Cs3Cu2I5 Single Crystal for Efficient Direct X-ray Detection

Cs3Cu2I5 Single Crystal for Efficient Direct X-ray Detection | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Cs 3 Cu 2 I 5 Single Crystal for Efficient Direct X-ray Detection Wei Qinhua, Fan Xiongsheng, Xiang Peng, Qin Laishun, Liu Wenjun, and 10 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2481952/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Low-dimensional copper-based halide perovskite single crystals are considered excellent scintillators for indirect X-ray detection, but their potential in direct X-ray detection has not been investigated. Herein, high-quality pure Cs 3 Cu 2 I 5 and Li-doped Cs 3 Cu 2 I 5 :Li single crystals are grown by the Bridgman method. The Li + dopant enhances the photoelectric properties of the Cs 3 Cu 2 I 5 single crystal by extending the carrier life time, improving the carrier mobility from 6.49 to 9.52 cm 2 V -1 s -1 , and increasing the mobility-lifetime (μτ) product from 1.4×10 -4 to 2.9×10 -4 cm 2 V –1 . The sensitive direct X-ray detector with a vertical device configuration of Au/Cs 3 Cu 2 I 5 :Li single crystal/PCBM/Au is fabricated and demonstrated to have a high sensitivity of 831.1 µC Gy air -1 cm -2 and low detection limit of 34.8 nGy air s -1 . Furthermore, the detector shows fast response, negligible baseline current drift and excellent stability upon X-ray illumination. Physical sciences/Materials science/Materials for devices/Electronic devices Physical sciences/Optics and photonics/Optical physics/X-rays Copper-based halides perovskite semiconductor Cs3Cu2I5:Li single crystal direct X-ray detection Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction X-ray imaging is widely used in medical diagnosis and treatment 1 , such as digital radiographic (DR) 2 and computerized tomography (CT) 3 . However, a high radiation dose poses health and cancer hazards and so low-dose X-ray imaging is highly desirable. There are indirect and direct approaches in X-ray imaging 4 . The indirect converter with a typical sensitivity of 0.3 µC Gy air –1 cm –2 is more prevalent but suffers from low spatial resolution and quantum efficiency due to inevitable visible light scattering. On the other hand, although the direct converter composed of semiconducting materials is able to monitor the X-ray excited charges 5 with higher sensitivity and spatial resolution in low-dose X-ray imaging, conventional semiconducting materials have some limitations and deficiencies. For instance, Si 6 and α-Se 7 lack sufficient stopping power for X-ray, consequently hindering operation in the high-energy range and HgI 2 8 detectors are plagued by the large leakage currents and low stability. CdZnTe 9 has shown great potential in room-temperature X-ray detection, there are drawbacks such as non-uniform charge transport and larger noise. In addition, the complicated preparation process and high fabrication cost pose practical challenges 10 . Recently, halide perovskites possessing attractive properties, such as large radiation attenuation coefficients, high carrier mobility life product (μτ), tunable band gap and bulk resistivity, and high fluorescence yields 11,12 , have been proposed to be efficient direct X-ray irradiation detectors 13 . However, common lead halide organic-inorganic perovskites suffer from the poor environmental stability and toxicity of lead-based salts 14,15 , Lead-free Copper-based halide perovskites show large radiation attenuation, high photoluminescence quantum yield (PLQY), lack of self-absorption, and good air-stability 16 17 18 , rendering it suitable for X-ray imaging and γ-ray detection, especially the zero-dimensional (0D) Cs 3 Cu 2 I 5 crystal. For example, clear reconstructed 3D snail CT images have been obtained by the Cs 3 Cu 2 I 5 nanocrystal-based fiber-optic panel 19 . The Cs 3 Cu 2 I 5 :Tl single crystal simultaneously exhibits high scintillation yield and remarkable energy resolution under 137 Cs γ-ray radiation in conjunction with low detection limit and afterglow in indirect X-ray detection 20,21 . The Li + -doped Cs 3 Cu 2 I 5 single crystal also has an excellent figure-of-merit, which can be used in the field of dual gamma-ray and neutron detection 22 . Moreover, the Cs 3 Cu 2 I 5 :In single crystal-based imaging system has excellent spatial resolution 23 . Because of the Cs 3 Cu 2 I 5 is constructed with [Cu 2 I 5 ] 3- coordinated polyhedron, spatially separated by Cs + that only serves as a skeleton to form the localized electronic structure 24 . The beneficial disrupted ion migration channels avoid the dark current noise and baseline drift problems at high bias voltages 25 , thereby maintaining the resolution and stability of the Cs 3 Cu 2 I 5 -based detector. In direct X-ray detection by the Cs 3 Cu 2 I 5 single crystal, the semiconductor converts X-ray into electrical signals with high sensitivity and spatial resolution. However, because of the larger band-gap of the Cs 3 Cu 2 I 5 single crystal and poor electrical properties, the capability of Cs 3 Cu 2 I 5 in direct X-ray detection has not been studied systematically. In this work, the strategy of Li + -doped was adopted to enhance the photoelectric properties of Cs 3 Cu 2 I 5 single crystal by extending the carrier life time and improving the carrier mobility. The pure Cs 3 Cu 2 I 5 and Li-doped Cs 3 Cu 2 I 5 :Li single crystals with a diameter of 12 mm are prepared by the Bridgman method and their properties pertaining to direct X-ray detection are investigated. The pure Cs 3 Cu 2 I 5 single crystal has moderate electronic properties such as carrier mobility of 6.49 cm 2 V -1 s -1 and mobility-lifetime (μτ) product of 1.4×10 -4 cm 2 V –1 . Doping with lithium improves optical-electrical properties including bigger carrier mobility of 9.52 cm 2 V -1 s -1 and mobility-lifetime (μτ) product of 2.9×10 -4 cm 2 V –1 . Subsequently, the direct X-ray detector assembled with the Cs 3 Cu 2 I 5 :Li single crystal shows a high sensitivity of 831.1 µC Gy air -1 cm -2 and low detection limit of 34.8 nGyair s -1 . The detector also exhibits excellent stability with negligible current drifts during continuous X-ray exposure. Results Crystal Growth and First-Principle Calculation. Figure 1 a presents the schematic diagram of the custom vertical Bridgman growth furnace with three zones. The temperature gradient can be adjusted from 10°C to 25°C for a length of 40 mm and the descending speed can be adjusted up to 0.001 mm/h. The pure Cs 3 Cu 2 I 5 and 2.5 at% Li + -doped Cs 3 Cu 2 I 5 :Li single crystals are grown by the self-seeding Bridgman technique with a capillary tube. The as-grown Cs 3 Cu 2 I 5 :Li single crystal ingots with a diameter of 12 mm and transparent machined sample without cracks and visible inclusions are exhibited in Fig. 1 a. The actual Li + doped concentration was confirmed by ICP-OES measurement. The actual Li + concentration is about 0.92 at% for 2.5 at% Li + -doped Cs 3 Cu 2 I 5 crystal, indicating that the Li + was introduced successfully. The powder XRD pattern of the polycrystalline Cs 3 Cu 2 I 5 :Li can be indexed to the pure Cs 3 Cu 2 I 5 PDF card #45–0077 revealing the absence of impurity phases like CsI or CuI, as shown in Fig. 1 b. Cs 3 Cu 2 I 5 crystallizes into the orthorhombic space group of Pnma at room temperature. Consider for the radius of Li + (0.59 Å) is closer to that of Cu + (0.60 Å), the Li + exhibits a tendency to substitute for the Cu + site. To gain mechanistic insights into the optical properties of the Li + doped effect on Cs 3 Cu 2 I 5 single crystals, the electronic band structures are derived by density-functional theory (DFT) calculation with the PBE hybrid functional. Both the valence band edges in Figs. 1 c and d are completely flat between the F and Z direction, which differ from the large bandwidth and dispersion band edges of conventional 3D structures. The direct band-gap of Cs 3 Cu 2 I 5 is smaller than that of Li + -doped Cs 3 Cu 2 I 5 , indicating a broken symmetry after introducing Li + to enlarge the band-gap. According to the DOS and PDOS map, the valence band maximum (VBM) is mainly contributed by the I-p orbitals and some Cu-d orbitals. Whereas, the conduction band minimum (CBM) density states are mainly composed of Cu-4s and I-5p orbitals. The flat VBM energy profiles of pure and Li + -doped Cs 3 Cu 2 I 5 indicate localized charge distributions corresponding to the charge density maps of VBM and CBM (Figs. 1 e and f). In particular, most of the charges of Li + -doped Cs 3 Cu 2 I 5 transfer from the [LiI 6 ] octahedrons to [CuI 6 ] octahedrons while some charges transfer from the metal to halide upon photoexcitation from VBM to CBM as shown in Fig. 1 f marked with red circle. Compared to the pure Cs 3 Cu 2 I 5 , more prominent charge transfer in Li + -doped Cs 3 Cu 2 I 5 enhances the conductivity and doping with Li extends the carrier lifetime and improves the carrier mobility. Optical properties of pure and Li + -doped Cs 3 Cu 2 I 5 single crystal. The survey XPS spectrum of Cs 3 Cu 2 I 5 :Li crystal in Fig. 2 a reveals the C 1s, Cs 3d, Cu 2p, and I 3d components and the high-resolution spectra are conducted to validate the chemical states of matrix ions. The binding energies of Cu 2p 1/2 and Cu 2p 3/2 are consistent with Cu-I bond and demonstrate the presence of Cu + in the host. The satellite peak for the Cu 2+ oxidation state cannot be observed. The binding energies of the 3d orbital correspond to the Cs and I + 1 and − 1 states, respectively. Compared to the XPS result of Cs 3 Cu 2 I 5 crystal, presenting in Figure S1, the Li + doped has no influence on chemical states of the crystal composition, except that the peaks position has a slight shift of 0.4 eV. The PLE and PL spectra of pure Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li single crystals was measured and shown in Fig. 2 b while the time resolved PL decay time curves were shown in Fig. 2 c. After Li + doping, the excitation (at 310 nm) and emission (at 445 nm) bands do not show obvious changes, but the decay time becomes slightly longer from 1002 ns to 1015 ns, indicating that the Li + -doped Cs 3 Cu 2 I 5 crystal has a longer electron-hole recombination time. Hence, the mobility-lifetime (µτ) product increases with Li + doping boding well for direct X-ray detection. Figures 2 d and e present the ultraviolet-visible absorption spectra of the pure and Li + -doped Cs 3 Cu 2 I 5 sample, respectively. The inset is the Tauc plot curve converted by the Kubelka-Munk equation for the band gap calculation 26 . Both the pure and Li + -doped Cs 3 Cu 2 I 5 exhibit a sharp absorption edge indicative of a direct band gap. The corresponding band gap energy ( E g ) of Cs 3 Cu 2 I 5 :Li is estimated to be 3.62 eV, which is bigger than that of the pure Cs 3 Cu 2 I 5 crystal (3.57 eV) and slightly exceeds that of the conventional semiconductor X-ray detector 27 . This trend is in good agreement with the DFT calculation shown in Figs. 1 c and d. Electronic properties of the Cs 3 Cu 2 I 5 single crystal. The carrier mobility is an important factor for X-ray detection, and the Hall-effect measurement was used to investigate the electronic properties of pure and Cs 3 Cu 2 I 5 :Li single crystal. Two samples exhibit n-type conductivity. The Cs 3 Cu 2 I 5 :Li single crystal has higher carrier mobility of 9.52 cm 2 V − 1 s − 1 than the pure Cs 3 Cu 2 I 5 single crystal (6.49 cm 2 V − 1 s − 1 ), and it is larger than that of Cs 3 Bi 2 Br 9 (1.54 cm 2 V − 1 s − 1 ) 28 and two times that of Cs 2 AgBiBr 6 (3.17 cm 2 V − 1 s − 1 ) 29 and MAPbBr 3 (4.16 cm 2 V − 1 s − 1 ) 30 . It means that the Li dopant enhances the conductivity of the Cs 3 Cu 2 I 5 single crystal, and the positive effect on the conductivity is confirmed by experiments and DFT calculation. The pure Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li single crystal ingots are machined into squares and integrated into X-ray detectors with the stacked structure of Au/Cs 3 Cu 2 I 5 or Cs 3 Cu 2 I 5 :Li/PCBM/Au and level alignment as shown in Fig. 3 a. Figure 3 b compares the absorption coefficients of typical and potential materials for X-ray detection, which were calculated according to the photon cross-section database 31 . Since Cs 3 Cu 2 I 5 consisting of heave elements of Cs, Cu, and I have a large high density (4.52 g cm − 3 ), it has a bigger X-ray absorption coefficient than Cs 2 AgBiBr 6 , α-Se, and commercial silicon, and comparable with CdTe. The photoconductivity measurements are carried out to determine the optoelectronic properties of the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li single crystal, as shown in Fig. 3 c. The photocurrent response is monitored by applying a voltage ranging from 0 to 60 V and the Hecht formula is employed to fit the photocurrent-voltage curve: I = I 0 µτV/L 2 (1-exp(-L 2 /µτV)) where I 0 is the saturated current, L is the thickness of the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li single crystal, and V is the applied voltage. The µτ products of the pure Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li single crystal are determined to be 1.4×10 − 4 cm 2 V − 1 and 2.9×10 − 4 cm 2 V − 1 , respectively, and the bigger µτ product indicates enhanced transport of photogenerated charges. Moreover, the Cs 3 Cu 2 I 5 :Li single crystal has a smaller resistivity of 2.7×10 10 Ω cm compared to 4.3×10 11 Ω cm of the Cs 3 Cu 2 I 5 single crystal, as shown in Fig. 3 (d). Figure 3 (e) shows the current density-voltage (J-V) characteristics of the X-ray detectors made of the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li single crystals. The Cs 3 Cu 2 I 5 X-ray detector exhibits obviously lower dark currents than Cs 3 Cu 2 I 5 :Li due to the high resistivity, and the dark current mainly comes from the injected current form the electrodes at the applied electric field. Meanwhile, the Cs 3 Cu 2 I 5 :Li X-ray detector shows a significantly enhanced light current of 2.0×10 − 8 A cm − 2 at an electric field of 45 V/mm, which is more than twice that of the Cs 3 Cu 2 I 5 X-ray detector of 9.3×10 − 9 A cm − 2 . The light current originates from the X-ray excited photocurrent, and the Li-doped Cs 3 Cu 2 I 5 :Li single crystal possesses higher conductivity due to enhanced charge transport thus facilitating high-sensitivity X-ray detection. Direct X-ray detection. To obtain dynamic information from the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li X-ray detectors, the time-resolved light current response for various X-ray dose rates from 1579 µGy air s − 1 to 82 µGy air s − 1 are presented in Fig. 4 a, the inset is the picture of detector. Both detectors show decent response signals upon on/off X-ray switching and good linear relationship with the X-ray dose rates. The Cs 3 Cu 2 I 5 :Li X-ray detector exhibits obviously higher dark currents and light currents with larger X-ray on-off than the pure Cs 3 Cu 2 I 5 detector at an electric field of 45 V/mm, indicating the Cs 3 Cu 2 I 5 :Li X-ray detector has more sensitive X-ray detection properties. Figure S2 presents the current response of the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li detectors during X-ray on/off at different electric fields and X-ray dose rates. To investigate the sensitivity of the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li X-ray detectors, the X-ray generated photocurrent density are plotted as a function of X-ray dose rates as shown in Figs. 4 b and 4 c. The sensitivity of the X-ray detector can be calculated from the slope of the photocurrents versus X-ray dose rates plots acquired at different electric fields. The pure Cs 3 Cu 2 I 5 detector has X-ray sensitivities of 441.5 µC Gy air −1 cm − 2 , 363.3 µC Gy air −1 cm − 2 , 288.5 µC Gy air −1 cm − 2 , 233.1 µC Gy air −1 cm − 2 and 168.9 µC Gy air −1 cm − 2 at 45, 37, 30, 28 and 15 V/mm, respectively. In comparison, the Cs 3 Cu 2 I 5 :Li X-ray detector shows enhanced sensitivities of 831.1 µC Gy air −1 cm − 2 , 661.8 µC Gy air −1 cm − 2 , 422.0 µC Gy air −1 cm − 2 , 311.5 µC Gy air −1 cm − 2 and 95.6 µC Gy air −1 cm − 2 at electric fields of 45, 37, 30, 28 and 15 V/mm, respectively. The signal-to-noise ratio (SNR) is another important parameter for X-ray detection and can be calculated by the following equation: SNR = I signal / I noise = (I photo – I dark ) / I noise , where I photo is the average current during X-ray irradiation, I dark is the average dark current derived from parallel experiments at each bias, and I noise is the noise current calculated from the standard deviation of the photocurrents. The SNRs of the X-ray detectors at an electric field of 45 V/mm are plotted as a function of dose rates in Fig. 4 d, and a linear dependence with X-ray dose rates is observed. According to the International Union of Pure and Applied Chemistry standard, the detector signal should maintain an SNR of over 3. The Cs 3 Cu 2 I 5 :Li X-ray detector has a smaller limit-of-detection (LoD) of 34.8 nGy air s − 1 than the pure Cs 3 Cu 2 I 5 X-ray detector of 335.1 nGy air s − 1 , which is consistent with the higher sensitivity of the Cs 3 Cu 2 I 5 :Li X-ray detector. Then, we highlight the performance of perovskite based X-ray direct conversion detectors and summarize the important parameters including the µτ product, sensitivity, detection limit and resistivity in Table S1. The Cs 3 Cu 2 I 5 :Li crystal presents good comprehensive performance. To evaluate the detection stability under continuous operating conditions, X-ray on/off experiments are carried out at the 45 V/mm external electric field and 1579 µGy air s − 1 X-ray dose for 3600 s as shown in Figs. 4 e and S3. Both the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li X-ray detectors exhibit reproducible and stable response with small X-ray on/off changes, indicating excellent materials and working stability under continuous X-ray exposure. The temporal baseline tracking of the X-ray detectors shown in Figure S4, and the current drift (I drift ) can be calculated by the following equation: I drift = (I t – I 0 ) / (E×S×t), where I t is the current at time t, I 0 is the current immediately after stabilization, E is the electric field, and S is the area of the device. Both the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li X-ray detectors are able to maintain stable dark and light currents in 3600 s, and both of the Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 :Li X-ray detectors show smaller light current drifts of 1.17×10 − 4 A cm – 1 s – 1 V –1 and 1.35×10 − 4 A cm – 1 s – 1 V – 1 , indicating excellent working stability. The X-ray imaging capability of the Cs 3 Cu 2 I 5 :Li X-ray detector is assessed by x-y scanning experiments with a key containing a plastic handle and metal bit as the imaging target. As shown in Fig. 4 f, the X-ray image clearly reveals a clear outline of the key consistent with the optical image in the scanning mode. Conclusion The pure Cs 3 Cu 2 I 5 and Li + -doped Cs 3 Cu 2 I 5 :Li single crystals are studied for high sensitivity direct X-ray detection. The high quality pure Cs 3 Cu 2 I 5 single crystal with a size of 12 mm is grown by the Bridgman method, and doped with Li + to form Cs 3 Cu 2 I 5 :Li single crystal. The pure Cs 3 Cu 2 I 5 single crystal shows moderate electronic properties with carrier mobility of 6.49 cm 2 V -1 s -1 and mobility-lifetime (μτ) product of 1.4×10 -4 cm 2 V –1 . In comparison, the Cs 3 Cu 2 I 5 :Li single crystal has significantly enhanced optical-electrical properties such as carrier mobility of 9.52 cm 2 V -1 s -1 and mobility-lifetime (μτ) product of 2.9×10 -4 cm 2 V –1 . The positive effect of Li + - doped on the properties of Cs 3 Cu 2 I 5 crystal is approved by experiments and DFT calculation. The physical mechanism need to be studied further. The efficient direct X-ray detector composed of the Cs 3 Cu 2 I 5 :Li single crystal (Au/Cs 3 Cu 2 I 5 :Li/PCBM/Au) shows a high sensitivity of 831.1 µC Gy air -1 cm -2 , low detection limit of 34.8 nGyair s -1 , and excellent stability under continuous X-ray illumination. The results demonstrate the high potential of the Cs 3 Cu 2 I 5 :Li single crystal in direct X-ray detection. Methods Materials. Anhydrous 99.999% pure CuI (ALDRICH) and 99.99% pure CsI and LiI (APL Engineered Materials, Inc.) were used as starting materials. The pure and 2.5at% Li + -doped Cs 3 Cu 2 I 5 crystals were grown by the Bridgman method. Owing to the similar Shannon radii, Li + is assumed to substitute for Cu + (d 10 ). The mixture was charged into a quartz crucible with a straight capillary on the bottom. The crucible was evacuated to a pressure 5×10 -5 Pa and sealed with an oxyhydrogen flame. The sealed ampoule was transferred to a three-zone Bridgman furnace and the temperature in the three-zone was 460°C, 480°C and 200°C, respectively. To completely melt the starting materials, the quartz crucible was held in the high-temperature zone for 40 h. The temperature gradient near the solid-liquid interface was 20 ℃/cm and the quartz crucible was descended at a speed of 0.5-1 mm/h. Finally, the furnace cooled to room temperature in 60 h to obtain the Cs 3 Cu 2 I 5 single crystal. Material characterization. The crystal structure and phases were determined on the SmartLab SE X-ray diffractometer with Cu Kα radiation (λ = 0.1541 nm). Inductively coupled plasma optical emission spectrometry (ICP-OES) (Agilent Technologies 5100) and X-ray photoelectron spectroscopy (XPS) (Thermo Scientific K-Alpha) were carried out to determine the chemical composition. The electronic properties were evaluated by Hall-effects using the PPMS-9 comprehensive physical property measurement system as well as photoconduction measurements. The photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra, and decay time data were obtained on an FLS1000 spectrometer with a pulsed nano-LED under UV light irradiation. The absorption spectra were acquired on the ultraviolet-visible spectrophotometer (UV2600, SDPTOP). Computation details. The density functional theory computations were performed using the Vienna Ab-initio Simulation Package(VASP) 32 33 34 35 . The hybrid exchange-correlation functional Perdew, Burke, and Ernzerhof (PBE) 36 together with the projected augmented wave (PAW) potentials 37,38 was employed in the current calculations to better reproduce the band structures 39 . The total density of states (DOS) and projected DOS (PDOS) vacancy defects of Cs, Cu, Li and I were calculated by the DFT-PBE level. The wavefunctions expanded in plane waves were cut off to a 550 eV kinetic energy and the Brillouin zone was sampled using a Γ-centred 2×2×2 k-mesh, which was examined to have good convergence against denser k-points. Detector performance. The X-ray detection properties of the detector were evaluated using an X-ray generation system for medical imaging (Varex, G242, 18932-M8, USA) at an accelerating voltage of 50 kV and currents are ranging from 10 to 200 uA. The dose rate of the X-rays was calibrated with an X2 CT dosimeter (Unfors Raysafe, Sweden). During the measurement, the environment was kept dark and the external electrical bias and current were recorded by the PDA FS380 semiconductor analyzer. The X-ray imaging capability of the detector was demonstrated by moving the object between the detector (1 mm 2 ) and X-ray beam (1.62 mGy air s -1 ) using a self-assembled x-y scanning system consisting of a motorized linear displacement stage (Newport, M-IMS400CC. A motorized linear displacement stage combined with a motion controller (Newport, M-IMS400CC) was used to control scanning along the x and y axes. Declarations Acknowledgements The authors acknowledge the financial support provided by the National Natural Science Foundation of China (NSFC) (No. 12275262, 21975280, 62004091 and 12235006), Natural Science Foundation of Zhejiang (No. Z23E020002, LGG22E020001), Shenzhen Excellent Science and Technology Innovation Talent Training Project-Outstanding Youth Project (RCJC20200714114435061), Shenzhen Basic Research Program (JCYJ20200109115212546), Chinese Academy of Sciences Special Research Assistant Project (Y95909), Chinese Academy of Sciences Excellent Youth Innovation Fund grade B (E2G0161001). City University of Hong Kong Donation Research Grant (DON-RMG 9229021), City University of Hong Kong Donation Grant (9220061), Hong Kong PDFS - RGC Postdoctoral Fellowship Scheme (PDFS2122-1S08 and CityU 9061014), as well as Hong Kong HMRF (Health and Medical Research Fund) (2120972 and CityU 9211320). The authors also acknowledge Professor Jiang Tang of Huazhong University of Science and Technology for his useful advice. References Ou, X. et al. Recent Development in X-Ray Imaging Technology: Future and Challenges. Research 2021, 9892152, doi: 10.34133/2021/9892152 (2021). Lee, S. M. et al. Deep Learning Applications in Chest Radiography and Computed Tomography: Current State of the Art. Journal of Thoracic Imaging 34 (2019). Mei, X. et al. Artificial intelligence–enabled rapid diagnosis of patients with COVID-19. Nature Medicine 26 , 1224–1228, doi: 10.1038/s41591-020-0931-3 (2020). Wu, H., Ge, Y., Niu, G. & Tang, J. Metal Halide Perovskites for X-Ray Detection and Imaging. 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Cs 2 AgBiBr 6 single-crystal X-ray detectors with a low detection limit. Nature Photonics 11 , 726–732, doi: 10.1038/s41566-017-0012-4 (2017). Li, L. et al. Enhanced X-ray Sensitivity of MAPbBr 3 Detector by Tailoring the Interface-States Density. ACS Appl. Mater. Interfaces 11 , 7522–7528, doi: 10.1021/acsami.8b18598 (2019). Berger, M. J. et al. XCOM: photon cross sections database. NIST http://physics.nist.gov/xcom, (2013). Kresse, G. & Hafner, J. Ab initio molecular dynamics for liquid metals. Physical Review B 47 , 558–561, doi: 10.1103/PhysRevB.47.558 (1993). Kresse, G. & Hafner, J. Ab initio molecular-dynamics simulation of the liquid-metal–amorphous-semiconductor transition in germanium. Physical Review B 49 , 14251–14269, doi: 10.1103/PhysRevB.49.14251 (1994). Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science 6 , 15–50, doi: https://doi.org/10.1016/0927-0256(96)00008-0 (1996). Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Physical Review B 54 , 11169–11186, doi: 10.1103/PhysRevB.54.11169 (1996). Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized Gradient Approximation Made Simple. Physical Review Letters 77 , 3865–3868, doi: 10.1103/PhysRevLett.77.3865 (1996). Blöchl, P. E. Projector augmented-wave method. Physical Review B 50 , 17953–17979, doi: 10.1103/PhysRevB.50.17953 (1994). Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B 59 , 1758–1775, doi: 10.1103/PhysRevB.59.1758 (1999). Paier, J., Hirschl, R., Marsman, M. & Kresse, G. The Perdew–Burke–Ernzerhof exchange-correlation functional applied to the G2-1 test set using a plane-wave basis set. The Journal of Chemical Physics 122 , 234102, doi: 10.1063/1.1926272 (2005). Additional Declarations There is NO Competing Interest. Supplementary Files SupportingInformation.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-2481952","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":167998972,"identity":"b76e91fe-1113-4bd0-8e19-ea1d76c53b5f","order_by":0,"name":"Wei Qinhua","email":"","orcid":"","institution":"College of Materials and Chemistry, China Jiliang University, Hangzhou 310018, China","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Qinhua","suffix":""},{"id":167998973,"identity":"d89dd156-0e45-4b37-b596-70e17b643fb4","order_by":1,"name":"Fan Xiongsheng","email":"","orcid":"","institution":"Materials Interfaces Center,Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Fan","middleName":"","lastName":"Xiongsheng","suffix":""},{"id":167998974,"identity":"561cc485-9ffd-43d8-b84e-5872a351c781","order_by":2,"name":"Xiang Peng","email":"","orcid":"","institution":"College of Materials and Chemistry, China Jiliang University","correspondingAuthor":false,"prefix":"","firstName":"Xiang","middleName":"","lastName":"Peng","suffix":""},{"id":167998975,"identity":"041ca7f3-26d8-40da-95c1-4fc5869c9198","order_by":3,"name":"Qin Laishun","email":"","orcid":"","institution":"College of Materials and Chemistry, China Jiliang University","correspondingAuthor":false,"prefix":"","firstName":"Qin","middleName":"","lastName":"Laishun","suffix":""},{"id":167998976,"identity":"e13f76a7-f7be-46b3-99a5-813cacf48d1d","order_by":4,"name":"Liu Wenjun","email":"","orcid":"","institution":"Materials Interfaces Center, Shenzhen Institute of Advanced 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Sciences","correspondingAuthor":false,"prefix":"","firstName":"Liu","middleName":"","lastName":"Yanliang","suffix":""},{"id":167998986,"identity":"79b0e75c-3f81-4b7b-91b9-a7c0ccdea2ca","order_by":14,"name":"Xue-Feng Yu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvklEQVRIiWNgGAWjYDAC5gNAooKBhwQtbAlA4gxQCxtJWhjbQAxidRgcY2CT5p1XJ8M/v4Hxww8GuzyCWiTbQFq2HeaROMbALNnDkFxMUAu/fANIywEehmMMDNIMDAcSGwhpYWMD2TKnjkceaMtvorTwg7U0MPOAPUWUFsk2xmbLOccO8xgeS2yz7DFIJqzF4BjzwRtvaurs5Q4fPnzjR4UdYS3ASGmRgDKAig0IqwcB5g/EqRsFo2AUjIIRCwCCkTAE4/npDAAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0003-2566-6194","institution":"Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences","correspondingAuthor":true,"prefix":"","firstName":"Xue-Feng","middleName":"","lastName":"Yu","suffix":""}],"badges":[],"createdAt":"2023-01-16 02:20:47","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2481952/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2481952/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":31695444,"identity":"c43ac2b8-fb54-4a6c-a120-ff7a3ca8d678","added_by":"auto","created_at":"2023-01-17 16:15:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1065682,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of the vertical Bridgman furnace for crystal growth and photographs of the as-grown Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5 \u003c/sub\u003eand\u003csub\u003e \u003c/sub\u003eCs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystals and machined samples. (b) Powder XRD pattern of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li. Electronic band structure of (c) pure and (d) Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e. Charge density maps of VBM and CBM of (e) pure and (f) Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-2481952/v1/2c0f2899defec68e0b0c525a.png"},{"id":31696173,"identity":"69e53c2e-de90-4154-a179-53f7b40e2c38","added_by":"auto","created_at":"2023-01-17 16:23:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":3195000,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XPS survey spectrum of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li and High-resolution XPS spectra of Cs 3d, Cu 2p and I 3d. (b) Photoluminescence emission and excitation spectra and (c) Decay profiles of pure and Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e. Absorption spectra of (d) pure and (e) Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e (Inset: Tauc plot showing the direct bandgap).\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-2481952/v1/1188d929e9c91c3d024c55dc.png"},{"id":31695443,"identity":"dc9db617-d14d-4cf0-8831-be90731a425c","added_by":"auto","created_at":"2023-01-17 16:15:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":164838,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic of X-ray detector fabrication and device configuration, Calculated attenuation coefficient of various semiconductors for different X-ray energy (b), (c) Photoconductivity, (d) resistivity spectra of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li. (e) J-V characteristics of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li assisted X-ray detectors.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-2481952/v1/a52e889664d73f6921526d2b.png"},{"id":31695442,"identity":"afc6c9a4-8f3b-4086-aa40-16cc8a3d9a02","added_by":"auto","created_at":"2023-01-17 16:15:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2097679,"visible":true,"origin":"","legend":"\u003cp\u003e(a) X-ray response of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li assisted X-ray detectors and the picture of detector. Current densities generated by X-ray as a function of dose rates at different applied electrical fields for (b) Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and (c) Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li detectors. (d) Dose rate dependent SNR of the detectors. (e) Stability of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li detector under pulsed X-ray irradiation at a fixed dose rate. (f) Optical and X-ray images of a metallic key.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-2481952/v1/2139fc16cda6062b70a71308.png"},{"id":31751951,"identity":"1b6e2306-761a-44b1-90d9-750ad7b0fd4b","added_by":"auto","created_at":"2023-01-18 14:47:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1735934,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2481952/v1/b56c730f-2c97-48b0-8971-673286def1d0.pdf"},{"id":31695446,"identity":"662ced34-d0f5-4fc9-b71b-7a7593ebb4d1","added_by":"auto","created_at":"2023-01-17 16:15:01","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":14778454,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-2481952/v1/89c3e8aee44d624c872dbba3.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003eCs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e Single Crystal for Efficient Direct X-ray Detection\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eX-ray imaging is widely used in medical diagnosis and treatment\u003csup\u003e1\u003c/sup\u003e, such as digital radiographic (DR)\u003csup\u003e2\u003c/sup\u003e and computerized tomography (CT)\u003csup\u003e3\u003c/sup\u003e. However, a high radiation dose poses health and cancer hazards and so low-dose X-ray imaging is highly desirable. There are indirect and direct approaches in X-ray imaging\u0026nbsp;\u003csup\u003e4\u003c/sup\u003e. The indirect converter with a typical sensitivity of 0.3 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026ndash;1\u003c/sup\u003e cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e is more prevalent but suffers from low spatial resolution and quantum efficiency due to inevitable visible light scattering. On the other hand, although the direct converter composed of semiconducting materials is able to monitor the X-ray excited charges\u003csup\u003e5\u003c/sup\u003e with higher sensitivity and spatial resolution in low-dose X-ray imaging, conventional semiconducting materials have some limitations and deficiencies. For instance, Si\u003csup\u003e6\u003c/sup\u003e\u003csup\u003e\u0026nbsp;\u003c/sup\u003eand \u0026alpha;-Se\u003csup\u003e7\u003c/sup\u003e lack sufficient stopping power for X-ray,\u0026nbsp;consequently hindering operation\u0026nbsp;in the high-energy range\u0026nbsp;and\u0026nbsp;HgI\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e8\u003c/sup\u003e\u003csup\u003e\u0026nbsp;\u003c/sup\u003edetectors\u0026nbsp;are plagued by the\u0026nbsp;large leakage currents and low stability. CdZnTe\u003csup\u003e9\u003c/sup\u003e has\u0026nbsp;shown\u0026nbsp;great potential in room-temperature X-ray detection,\u0026nbsp;there are drawbacks such as\u0026nbsp;non-uniform charge transport and larger noise.\u0026nbsp;In addition,\u0026nbsp;the complicated preparation process and high fabrication cost\u0026nbsp;pose practical\u0026nbsp;challenges\u0026nbsp;\u003csup\u003e10\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRecently, halide perovskites possessing\u0026nbsp;attractive\u0026nbsp;properties, such as large radiation attenuation coefficients,\u0026nbsp;high\u0026nbsp;carrier mobility life product (\u0026mu;\u0026tau;), tunable band gap and bulk resistivity, and high fluorescence yields\u003csup\u003e11,12\u003c/sup\u003e,\u0026nbsp;have been proposed to be efficient direct X-ray\u0026nbsp;irradiation detectors\u003csup\u003e13\u003c/sup\u003e.\u0026nbsp;However, common lead halide organic-inorganic perovskites suffer from the poor environmental stability and toxicity of lead-based salts\u003csup\u003e14,15\u003c/sup\u003e, Lead-free Copper-based\u0026nbsp;halide perovskites\u0026nbsp;show\u0026nbsp;large radiation attenuation,\u0026nbsp;high photoluminescence quantum yield (PLQY), lack of self-absorption, and good air-stability\u003csup\u003e16\u003c/sup\u003e \u003csup\u003e17\u003c/sup\u003e \u003csup\u003e18\u003c/sup\u003e, rendering it suitable for X-ray imaging and \u0026gamma;-ray detection, especially the zero-dimensional (0D) Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e crystal. For example, clear reconstructed 3D snail CT images have been obtained by the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e nanocrystal-based fiber-optic panel\u003csup\u003e19\u003c/sup\u003e. The Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Tl single crystal simultaneously exhibits high scintillation yield and remarkable energy resolution under \u003csup\u003e137\u003c/sup\u003eCs \u0026gamma;-ray radiation in conjunction with low detection limit and afterglow in indirect X-ray detection\u003csup\u003e20,21\u003c/sup\u003e. The Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal\u0026nbsp;also\u0026nbsp;has an excellent figure-of-merit, which can be used in the field of dual gamma-ray and neutron detection\u003csup\u003e22\u003c/sup\u003e.\u0026nbsp;Moreover,\u0026nbsp;the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:In single crystal-based imaging system has excellent spatial resolution\u003csup\u003e23\u003c/sup\u003e. Because of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e is constructed with [Cu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e]\u003csup\u003e3-\u003c/sup\u003e coordinated polyhedron, spatially separated by Cs\u003csup\u003e+\u003c/sup\u003e that only serves as a skeleton to form the localized electronic structure\u003csup\u003e24\u003c/sup\u003e. The beneficial disrupted ion migration channels avoid the dark current noise and baseline drift problems at high bias voltages\u003csup\u003e25\u003c/sup\u003e, thereby maintaining the resolution and stability of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e-based detector. In direct X-ray detection by the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal, the semiconductor converts X-ray into electrical signals with high sensitivity and spatial resolution. However, because of the larger band-gap of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal and poor electrical properties, the capability of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e in direct X-ray detection has not been studied systematically.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn this work, the strategy of Li\u003csup\u003e+\u003c/sup\u003e-doped was adopted to enhance\u0026nbsp;the photoelectric properties of\u0026nbsp;Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal by extending the carrier life time and improving the carrier mobility. The pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Li-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystals with a diameter of 12 mm are prepared by the Bridgman method and their properties pertaining to direct X-ray detection are investigated. The pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal has moderate electronic properties such as carrier mobility of 6.49 cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e-1\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e and mobility-lifetime (\u0026mu;\u0026tau;) product of\u0026nbsp;1.4\u0026times;10\u003csup\u003e-4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. Doping with lithium improves\u003csub\u003e\u0026nbsp;\u003c/sub\u003eoptical-electrical properties including bigger carrier mobility of 9.52\u0026nbsp;cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e-1\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e and mobility-lifetime (\u0026mu;\u0026tau;) product of\u0026nbsp;2.9\u0026times;10\u003csup\u003e-4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. Subsequently, the direct X-ray detector assembled with the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal shows a high sensitivity of\u0026nbsp;831.1\u0026nbsp;\u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e cm\u003csup\u003e-2\u003c/sup\u003e and low detection limit of\u0026nbsp;34.8\u0026nbsp;nGyair s\u003csup\u003e-1\u003c/sup\u003e. The detector also exhibits excellent stability with negligible current drifts during continuous X-ray exposure.\u0026nbsp;\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e \u003cb\u003eCrystal Growth and First-Principle Calculation.\u003c/b\u003e Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea presents the schematic diagram of the custom vertical Bridgman growth furnace with three zones. The temperature gradient can be adjusted from 10\u0026deg;C to 25\u0026deg;C for a length of 40 mm and the descending speed can be adjusted up to 0.001 mm/h. The pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and 2.5 at% Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystals are grown by the self-seeding Bridgman technique with a capillary tube. The as-grown Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal ingots with a diameter of 12 mm and transparent machined sample without cracks and visible inclusions are exhibited in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea. The actual Li\u003csup\u003e+\u003c/sup\u003e doped concentration was confirmed by ICP-OES measurement. The actual Li\u003csup\u003e+\u003c/sup\u003e concentration is about 0.92 at% for 2.5 at% Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e crystal, indicating that the Li\u003csup\u003e+\u003c/sup\u003e was introduced successfully. The powder XRD pattern of the polycrystalline Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li can be indexed to the pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e PDF card #45\u0026ndash;0077 revealing the absence of impurity phases like CsI or CuI, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb. Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e crystallizes into the orthorhombic space group of Pnma at room temperature. Consider for the radius of Li\u003csup\u003e+\u003c/sup\u003e (0.59 \u0026Aring;) is closer to that of Cu\u003csup\u003e+\u003c/sup\u003e (0.60 \u0026Aring;), the Li\u003csup\u003e+\u003c/sup\u003e exhibits a tendency to substitute for the Cu\u003csup\u003e+\u003c/sup\u003e site.\u003c/p\u003e \u003cp\u003eTo gain mechanistic insights into the optical properties of the Li\u003csup\u003e+\u003c/sup\u003e doped effect on Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystals, the electronic band structures are derived by density-functional theory (DFT) calculation with the PBE hybrid functional. Both the valence band edges in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and d are completely flat between the F and Z direction, which differ from the large bandwidth and dispersion band edges of conventional 3D structures. The direct band-gap of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e is smaller than that of Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e, indicating a broken symmetry after introducing Li\u003csup\u003e+\u003c/sup\u003e to enlarge the band-gap. According to the DOS and PDOS map, the valence band maximum (VBM) is mainly contributed by the I-p orbitals and some Cu-d orbitals. Whereas, the conduction band minimum (CBM) density states are mainly composed of Cu-4s and I-5p orbitals. The flat VBM energy profiles of pure and Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e indicate localized charge distributions corresponding to the charge density maps of VBM and CBM (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee and f). In particular, most of the charges of Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e transfer from the [LiI\u003csub\u003e6\u003c/sub\u003e] octahedrons to [CuI\u003csub\u003e6\u003c/sub\u003e] octahedrons while some charges transfer from the metal to halide upon photoexcitation from VBM to CBM as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef marked with red circle. Compared to the pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e, more prominent charge transfer in Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e enhances the conductivity and doping with Li extends the carrier lifetime and improves the carrier mobility.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eOptical properties of pure and Li\u003c/b\u003e \u003csup\u003e \u003cb\u003e+\u003c/b\u003e \u003c/sup\u003e \u003cb\u003e-doped Cs\u003c/b\u003e \u003csub\u003e \u003cb\u003e3\u003c/b\u003e \u003c/sub\u003e \u003cb\u003eCu\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003eI\u003c/b\u003e \u003csub\u003e \u003cb\u003e5\u003c/b\u003e \u003c/sub\u003e \u003cb\u003esingle crystal.\u003c/b\u003e The survey XPS spectrum of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li crystal in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea reveals the C 1s, Cs 3d, Cu 2p, and I 3d components and the high-resolution spectra are conducted to validate the chemical states of matrix ions. The binding energies of Cu 2p\u003csub\u003e1/2\u003c/sub\u003e and Cu 2p\u003csub\u003e3/2\u003c/sub\u003e are consistent with Cu-I bond and demonstrate the presence of Cu\u003csup\u003e+\u003c/sup\u003e in the host. The satellite peak for the Cu\u003csup\u003e2+\u003c/sup\u003e oxidation state cannot be observed. The binding energies of the 3d orbital correspond to the Cs and I\u0026thinsp;+\u0026thinsp;1 and \u0026minus;\u0026thinsp;1 states, respectively. Compared to the XPS result of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e crystal, presenting in Figure S1, the Li\u003csup\u003e+\u003c/sup\u003e doped has no influence on chemical states of the crystal composition, except that the peaks position has a slight shift of 0.4 eV. The PLE and PL spectra of pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystals was measured and shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb while the time resolved PL decay time curves were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec. After Li\u003csup\u003e+\u003c/sup\u003e doping, the excitation (at 310 nm) and emission (at 445 nm) bands do not show obvious changes, but the decay time becomes slightly longer from 1002 ns to 1015 ns, indicating that the Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e crystal has a longer electron-hole recombination time. Hence, the mobility-lifetime (\u0026micro;τ) product increases with Li\u003csup\u003e+\u003c/sup\u003e doping boding well for direct X-ray detection. Figures\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed and e present the ultraviolet-visible absorption spectra of the pure and Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e sample, respectively. The inset is the Tauc plot curve converted by the Kubelka-Munk equation for the band gap calculation\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. Both the pure and Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e exhibit a sharp absorption edge indicative of a direct band gap. The corresponding band gap energy (\u003cem\u003eE\u003c/em\u003e\u003csub\u003eg\u003c/sub\u003e) of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li is estimated to be 3.62 eV, which is bigger than that of the pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e crystal (3.57 eV) and slightly exceeds that of the conventional semiconductor X-ray detector \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. This trend is in good agreement with the DFT calculation shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and d.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eElectronic properties of the Cs\u003c/b\u003e \u003csub\u003e \u003cb\u003e3\u003c/b\u003e \u003c/sub\u003e \u003cb\u003eCu\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003eI\u003c/b\u003e \u003csub\u003e \u003cb\u003e5\u003c/b\u003e \u003c/sub\u003e \u003cb\u003esingle crystal.\u003c/b\u003e The carrier mobility is an important factor for X-ray detection, and the Hall-effect measurement was used to investigate the electronic properties of pure and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal. Two samples exhibit n-type conductivity. The Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal has higher carrier mobility of 9.52 cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e than the pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal (6.49 cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and it is larger than that of Cs\u003csub\u003e3\u003c/sub\u003eBi\u003csub\u003e2\u003c/sub\u003eBr\u003csub\u003e9\u003c/sub\u003e (1.54 cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003csup\u003e28\u003c/sup\u003e and two times that of Cs\u003csub\u003e2\u003c/sub\u003eAgBiBr\u003csub\u003e6\u003c/sub\u003e (3.17 cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003csup\u003e29\u003c/sup\u003e and MAPbBr\u003csub\u003e3\u003c/sub\u003e (4.16 cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003csup\u003e30\u003c/sup\u003e. It means that the Li dopant enhances the conductivity of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal, and the positive effect on the conductivity is confirmed by experiments and DFT calculation.\u003c/p\u003e \u003cp\u003eThe pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal ingots are machined into squares and integrated into X-ray detectors with the stacked structure of Au/Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e or Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li/PCBM/Au and level alignment as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb compares the absorption coefficients of typical and potential materials for X-ray detection, which were calculated according to the photon cross-section database\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Since Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e consisting of heave elements of Cs, Cu, and I have a large high density (4.52 g cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e), it has a bigger X-ray absorption coefficient than Cs\u003csub\u003e2\u003c/sub\u003eAgBiBr\u003csub\u003e6\u003c/sub\u003e, α-Se, and commercial silicon, and comparable with CdTe. The photoconductivity measurements are carried out to determine the optoelectronic properties of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec. The photocurrent response is monitored by applying a voltage ranging from 0 to 60 V and the Hecht formula is employed to fit the photocurrent-voltage curve:\u003c/p\u003e \u003cp\u003eI\u0026thinsp;=\u0026thinsp;I\u003csub\u003e0\u003c/sub\u003e\u0026micro;τV/L\u003csup\u003e2\u003c/sup\u003e(1-exp(-L\u003csup\u003e2\u003c/sup\u003e/\u0026micro;τV))\u003c/p\u003e \u003cp\u003ewhere I\u003csub\u003e0\u003c/sub\u003e is the saturated current, L is the thickness of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal, and V is the applied voltage. The \u0026micro;τ products of the pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal are determined to be 1.4\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2.9\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, and the bigger \u0026micro;τ product indicates enhanced transport of photogenerated charges. Moreover, the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal has a smaller resistivity of 2.7\u0026times;10\u003csup\u003e10\u003c/sup\u003e Ω cm compared to 4.3\u0026times;10\u003csup\u003e11\u003c/sup\u003e Ω cm of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d). Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(e) shows the current density-voltage (J-V) characteristics of the X-ray detectors made of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystals. The Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e X-ray detector exhibits obviously lower dark currents than Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li due to the high resistivity, and the dark current mainly comes from the injected current form the electrodes at the applied electric field. Meanwhile, the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detector shows a significantly enhanced light current of 2.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e A cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e at an electric field of 45 V/mm, which is more than twice that of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e X-ray detector of 9.3\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e A cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The light current originates from the X-ray excited photocurrent, and the Li-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal possesses higher conductivity due to enhanced charge transport thus facilitating high-sensitivity X-ray detection.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eDirect X-ray detection.\u003c/b\u003e To obtain dynamic information from the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detectors, the time-resolved light current response for various X-ray dose rates from 1579 \u0026micro;Gy\u003csub\u003eair\u003c/sub\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 82 \u0026micro;Gy\u003csub\u003eair\u003c/sub\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, the inset is the picture of detector. Both detectors show decent response signals upon on/off X-ray switching and good linear relationship with the X-ray dose rates. The Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detector exhibits obviously higher dark currents and light currents with larger X-ray on-off than the pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e detector at an electric field of 45 V/mm, indicating the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detector has more sensitive X-ray detection properties. Figure S2 presents the current response of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li detectors during X-ray on/off at different electric fields and X-ray dose rates.\u003c/p\u003e \u003cp\u003eTo investigate the sensitivity of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detectors, the X-ray generated photocurrent density are plotted as a function of X-ray dose rates as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec. The sensitivity of the X-ray detector can be calculated from the slope of the photocurrents versus X-ray dose rates plots acquired at different electric fields. The pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e detector has X-ray sensitivities of 441.5 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, 363.3 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, 288.5 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, 233.1 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e and 168.9 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e at 45, 37, 30, 28 and 15 V/mm, respectively. In comparison, the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detector shows enhanced sensitivities of 831.1 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, 661.8 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, 422.0 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, 311.5 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e and 95.6 \u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e at electric fields of 45, 37, 30, 28 and 15 V/mm, respectively.\u003c/p\u003e \u003cp\u003eThe signal-to-noise ratio (SNR) is another important parameter for X-ray detection and can be calculated by the following equation:\u003c/p\u003e \u003cp\u003eSNR\u0026thinsp;=\u0026thinsp;I\u003csub\u003e\u003cem\u003esignal\u003c/em\u003e\u003c/sub\u003e / I\u003csub\u003e\u003cem\u003enoise\u003c/em\u003e\u003c/sub\u003e = (I\u003csub\u003e\u003cem\u003ephoto\u003c/em\u003e\u003c/sub\u003e \u0026ndash; I\u003csub\u003e\u003cem\u003edark\u003c/em\u003e\u003c/sub\u003e) / I\u003csub\u003e\u003cem\u003enoise\u003c/em\u003e\u003c/sub\u003e,\u003c/p\u003e \u003cp\u003ewhere I\u003csub\u003e\u003cem\u003ephoto\u003c/em\u003e\u003c/sub\u003e is the average current during X-ray irradiation, I\u003csub\u003e\u003cem\u003edark\u003c/em\u003e\u003c/sub\u003e is the average dark current derived from parallel experiments at each bias, and I\u003csub\u003e\u003cem\u003enoise\u003c/em\u003e\u003c/sub\u003e is the noise current calculated from the standard deviation of the photocurrents. The SNRs of the X-ray detectors at an electric field of 45 V/mm are plotted as a function of dose rates in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed, and a linear dependence with X-ray dose rates is observed. According to the International Union of Pure and Applied Chemistry standard, the detector signal should maintain an SNR of over 3. The Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detector has a smaller limit-of-detection (LoD) of 34.8 nGy\u003csub\u003eair\u003c/sub\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e than the pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e X-ray detector of 335.1 nGy\u003csub\u003eair\u003c/sub\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is consistent with the higher sensitivity of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detector. Then, we highlight the performance of perovskite based X-ray direct conversion detectors and summarize the important parameters including the \u0026micro;τ product, sensitivity, detection limit and resistivity in Table S1. The Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li crystal presents good comprehensive performance.\u003c/p\u003e \u003cp\u003eTo evaluate the detection stability under continuous operating conditions, X-ray on/off experiments are carried out at the 45 V/mm external electric field and 1579 \u0026micro;Gy\u003csub\u003eair\u003c/sub\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e X-ray dose for 3600 s as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee and S3. Both the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detectors exhibit reproducible and stable response with small X-ray on/off changes, indicating excellent materials and working stability under continuous X-ray exposure. The temporal baseline tracking of the X-ray detectors shown in Figure S4, and the current drift (I\u003csub\u003e\u003cem\u003edrift\u003c/em\u003e\u003c/sub\u003e) can be calculated by the following equation:\u003c/p\u003e \u003cp\u003eI\u003csub\u003e\u003cem\u003edrift\u003c/em\u003e\u003c/sub\u003e = (I\u003csub\u003et\u003c/sub\u003e \u0026ndash; I\u003csub\u003e0\u003c/sub\u003e) / (E\u0026times;S\u0026times;t),\u003c/p\u003e \u003cp\u003ewhere I\u003csub\u003et\u003c/sub\u003e is the current at time t, I\u003csub\u003e0\u003c/sub\u003e is the current immediately after stabilization, E is the electric field, and S is the area of the device. Both the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detectors are able to maintain stable dark and light currents in 3600 s, and both of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detectors show smaller light current drifts of 1.17\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e A cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e s\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026ndash;1\u003c/sup\u003e and 1.35\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e A cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e s\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e V\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, indicating excellent working stability.\u003c/p\u003e \u003cp\u003eThe X-ray imaging capability of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li X-ray detector is assessed by x-y scanning experiments with a key containing a plastic handle and metal bit as the imaging target. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef, the X-ray image clearly reveals a clear outline of the key consistent with the optical image in the scanning mode.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystals are studied for high sensitivity direct X-ray detection. The high quality pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u0026nbsp;\u003c/sub\u003esingle crystal with a size of 12 mm is grown by the Bridgman method, and doped with\u0026nbsp;Li\u003csup\u003e+\u003c/sup\u003e to form Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal. The pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal shows moderate electronic properties with carrier mobility of 6.49 cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e-1\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e and mobility-lifetime (\u0026mu;\u0026tau;) product of 1.4\u0026times;10\u003csup\u003e-4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. In comparison, the\u0026nbsp;Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal has significantly enhanced\u0026nbsp;optical-electrical properties such as carrier mobility of 9.52 cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e-1\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e and mobility-lifetime (\u0026mu;\u0026tau;) product of 2.9\u0026times;10\u003csup\u003e-4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. The positive effect of Li\u003csup\u003e+\u003c/sup\u003e- doped on the properties of Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e crystal is approved by experiments and DFT calculation. The physical mechanism\u0026nbsp;need to be studied further. The efficient direct X-ray detector composed of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal (Au/Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li/PCBM/Au) shows a high sensitivity of\u0026nbsp;831.1\u0026nbsp;\u0026micro;C Gy\u003csub\u003eair\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e cm\u003csup\u003e-2\u003c/sup\u003e, low detection limit of\u0026nbsp;34.8\u0026nbsp;nGyair s\u003csup\u003e-1\u003c/sup\u003e, and excellent stability under continuous X-ray illumination. The results demonstrate the high potential of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li\u0026nbsp;single crystal\u0026nbsp;in direct X-ray detection.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eMaterials.\u003c/strong\u003e Anhydrous 99.999% pure CuI (ALDRICH) and 99.99% pure CsI\u003csub\u003e\u0026nbsp;\u003c/sub\u003eand LiI (APL Engineered Materials, Inc.) were used as starting materials. The pure and 2.5at% Li\u003csup\u003e+\u003c/sup\u003e-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u0026nbsp;\u003c/sub\u003ecrystals were grown by the Bridgman method. Owing to the similar Shannon radii, Li\u003csup\u003e+\u003c/sup\u003e is assumed to substitute for Cu\u003csup\u003e+\u0026nbsp;\u003c/sup\u003e(d\u003csup\u003e10\u003c/sup\u003e). The mixture was charged into a quartz crucible with a straight capillary on the bottom. The crucible was evacuated to a pressure 5\u0026times;10\u003csup\u003e-5\u003c/sup\u003e Pa and sealed with an oxyhydrogen flame.\u0026nbsp;The sealed ampoule was transferred to a three-zone Bridgman furnace and the temperature in the three-zone was 460\u0026deg;C, 480\u0026deg;C\u0026nbsp;and 200\u0026deg;C, respectively. To completely melt the\u0026nbsp;starting materials, the\u0026nbsp;quartz crucible\u0026nbsp;was held in the high-temperature zone for 40 h. The temperature gradient near the solid-liquid interface was\u0026nbsp;20 ℃/cm and the quartz crucible was descended at a speed of 0.5-1 mm/h. Finally, the\u0026nbsp;furnace\u0026nbsp;cooled to room temperature\u0026nbsp;in\u0026nbsp;60 h to obtain the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u0026nbsp;\u003c/sub\u003esingle crystal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterial characterization.\u003c/strong\u003e The crystal structure and phases were determined on the SmartLab SE X-ray diffractometer with Cu K\u0026alpha; radiation (\u0026lambda; = 0.1541 nm). Inductively coupled plasma optical emission spectrometry (ICP-OES) (Agilent Technologies 5100) and X-ray photoelectron spectroscopy (XPS) (Thermo Scientific K-Alpha) were carried out to determine the chemical composition. The electronic properties were evaluated by Hall-effects using the PPMS-9 comprehensive physical property measurement system as well as photoconduction measurements.\u0026nbsp;The photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra, and decay time\u0026nbsp;data\u0026nbsp;were\u0026nbsp;obtained\u0026nbsp;on an FLS1000 spectrometer with a pulsed nano-LED\u0026nbsp;under UV light irradiation.\u0026nbsp;The absorption spectra were acquired on the ultraviolet-visible spectrophotometer (UV2600, SDPTOP).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComputation details.\u0026nbsp;\u003c/strong\u003eThe density functional theory computations were performed using the Vienna Ab-initio Simulation Package(VASP)\u003csup\u003e32\u003c/sup\u003e \u003csup\u003e33\u003c/sup\u003e \u003csup\u003e34\u003c/sup\u003e \u003csup\u003e35\u003c/sup\u003e.\u003csup\u003e\u0026nbsp;\u003c/sup\u003eThe hybrid exchange-correlation functional Perdew, Burke, and Ernzerhof (PBE)\u003csup\u003e36\u003c/sup\u003e together with the projected augmented wave (PAW) potentials\u003csup\u003e37,38\u003c/sup\u003e was employed in the current calculations to better reproduce the band structures\u003csup\u003e39\u003c/sup\u003e. The total density of states (DOS) and projected DOS (PDOS) vacancy defects of Cs, Cu, Li and I were calculated by the DFT-PBE level. The wavefunctions expanded in plane waves were cut off to a 550 eV kinetic energy and the Brillouin zone was sampled using a \u0026Gamma;-centred 2\u0026times;2\u0026times;2 k-mesh, which was examined to have good convergence against denser k-points.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDetector performance.\u0026nbsp;\u003c/strong\u003eThe X-ray detection properties of the detector were evaluated using an X-ray generation system for medical imaging (Varex, G242, 18932-M8, USA) at an accelerating voltage of 50 kV and currents are ranging from 10 to 200 uA. The dose rate of the X-rays was calibrated with an X2 CT dosimeter (Unfors Raysafe, Sweden). During the measurement, the environment was kept dark and the external electrical bias and current were recorded by the PDA FS380 semiconductor analyzer. The X-ray imaging capability of the detector was demonstrated by moving the object between the detector (1 mm\u003csup\u003e2\u003c/sup\u003e) and X-ray beam (1.62 mGy\u003csub\u003eair\u003c/sub\u003e s\u003csup\u003e-1\u003c/sup\u003e) using a self-assembled x-y scanning system consisting of a motorized linear displacement stage (Newport, M-IMS400CC. A motorized linear displacement stage combined with a motion controller (Newport, M-IMS400CC) was used to control scanning along the x and y axes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge the financial support provided by the National Natural Science Foundation of China (NSFC) (No. 12275262, 21975280, 62004091 and 12235006), Natural Science Foundation of Zhejiang (No. Z23E020002, LGG22E020001), Shenzhen Excellent Science and Technology Innovation Talent Training Project-Outstanding Youth Project (RCJC20200714114435061), Shenzhen Basic Research Program (JCYJ20200109115212546), Chinese Academy of Sciences Special Research Assistant Project (Y95909), Chinese Academy of Sciences Excellent Youth Innovation Fund grade B (E2G0161001). City University of Hong Kong Donation Research Grant (DON-RMG 9229021), City University of Hong Kong Donation Grant (9220061), Hong Kong PDFS - RGC Postdoctoral Fellowship Scheme (PDFS2122-1S08 and CityU 9061014), as well as Hong Kong HMRF (Health and Medical Research Fund) (2120972 and CityU 9211320). The authors also acknowledge Professor Jiang Tang of Huazhong University of Science and Technology for his useful advice.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e\u003cspan\u003eOu, X. \u003cem\u003eet al.\u003c/em\u003e Recent Development in X-Ray Imaging Technology: Future and Challenges. \u003cem\u003eResearch\u003c/em\u003e 2021, 9892152, doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.34133/2021/9892152\u003c/span\u003e\u003c/span\u003e (2021).\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eLee, S. 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The Journal of Chemical Physics \u003cstrong\u003e122\u003c/strong\u003e, 234102, doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1063/1.1926272\u003c/span\u003e\u003c/span\u003e (2005).\u003c/span\u003e\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Copper-based halides perovskite, semiconductor, Cs3Cu2I5:Li single crystal, direct X-ray detection","lastPublishedDoi":"10.21203/rs.3.rs-2481952/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2481952/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLow-dimensional copper-based halide perovskite single crystals are considered excellent scintillators for indirect X-ray detection, but their potential in direct X-ray detection has not been investigated. Herein, high-quality pure Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e and Li-doped Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystals are grown by the Bridgman method. The Li\u003csup\u003e+\u003c/sup\u003e dopant enhances the photoelectric properties of the Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e single crystal by extending the carrier life time, improving the carrier mobility from 6.49 to 9.52 cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e-1\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e, and increasing the mobility-lifetime (μτ) product from 1.4×10\u003csup\u003e-4\u003c/sup\u003e to 2.9×10\u003csup\u003e-4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003eV\u003csup\u003e–1\u003c/sup\u003e. The sensitive direct X-ray detector with a vertical device configuration of Au/Cs\u003csub\u003e3\u003c/sub\u003eCu\u003csub\u003e2\u003c/sub\u003eI\u003csub\u003e5\u003c/sub\u003e:Li single crystal/PCBM/Au is fabricated and demonstrated to have a high sensitivity of 831.1 µC Gy\u003csub\u003eair\u003c/sub\u003e \u003csup\u003e-1\u003c/sup\u003e cm\u003csup\u003e-2\u003c/sup\u003e and low detection limit of 34.8 nGy\u003csub\u003eair\u003c/sub\u003e s\u003csup\u003e-1\u003c/sup\u003e. Furthermore, the detector shows fast response, negligible baseline current drift and excellent stability upon X-ray illumination.\u003c/p\u003e","manuscriptTitle":"Cs3Cu2I5 Single Crystal for Efficient Direct X-ray Detection","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-01-17 16:14:56","doi":"10.21203/rs.3.rs-2481952/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"50471081-1c6e-44e6-ae30-37d9d580f936","owner":[],"postedDate":"January 17th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":18462310,"name":"Physical sciences/Materials science/Materials for devices/Electronic devices"},{"id":18462311,"name":"Physical sciences/Optics and photonics/Optical physics/X-rays"}],"tags":[],"updatedAt":"2023-01-18T14:46:56+00:00","versionOfRecord":[],"versionCreatedAt":"2023-01-17 16:14:56","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2481952","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2481952","identity":"rs-2481952","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}