Distinct mechano- and piezochromic behaviors of thermally activated delayed fluorescence（4CzTPN）crystal

Distinct mechano- and piezochromic behaviors of thermally activated delayed fluorescence（4CzTPN）crystal | 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 Distinct mechano- and piezochromic behaviors of thermally activated delayed fluorescence（4CzTPN）crystal Yarong Gu, Long Li, Min Wu, Kai Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6794720/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 16 Oct, 2025 Read the published version in Scientific Reports → Version 1 posted 12 You are reading this latest preprint version Abstract Incorporating mechano-luminescence (MCL) into thermally activated delayed fluorescence (TADF) molecules represents a promising strategy for developing multifunctional mechanoluminescent materials. However, the controllable utilization of the versatile properties inherent in TADF molecules remains challenging due to the inherent difficulties in system design. Herein, we investigate the pressure modulation of the photophysical properties of 2,3,5,6-tetrakis(carbazol-9-yl)-1,4-dicyanobenzene (4CzTPN), a representative TADF emitter, through in situ high-pressure photoluminescence (PL), time-resolved PL, UV-visible spectra and infrared spectroscopy. The different mechanisms of a blue shift by grinding crystals and of a red shift under hydrostatic pressure are fully investigated. High-pressure time-resolved measurements show that the short fluorescence lifetime decreases and the lifetime of delayed fluorescence disappears beyond 3.0 GPa. Infrared spectra indicate the style of relative intensity for the infrared absorption peak of ν(C-H) transform significantly when the pressure is greater than 3.0 GPa, which would be the cause of the disappearance of delayed fluorescence. This study enriches the insights into mechanochromic and multifunctional materials. Physical sciences/Chemistry/Materials chemistry Physical sciences/Chemistry/Photochemistry Physical sciences/Chemistry/Physical chemistry Thermally activated delayed fluorescence materials Solid state fluorescence lifetime High pressure IR spectra OLED Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Mechanochromic luminescence (MCL) molecules, as a new type of smart material, have been widely applied in fields such as sensors, optoelectronic devices, and anti-counterfeiting inks, which has attracted extensive attention 1 – 5 . Under external force stimuli, such as pressing, grinding, friction, and shearing, these materials can exhibit unique luminescence changes. In the past few years, significant progress has been made in MCL materials. At the same time, metal-free modern luminescent organic materials with thermally activated delayed fluorescence (TADF) behavior have become one of the most attractive luminescent materials in the field of organic light-emitting diodes (OLEDs) 6 – 11 . Such materials can achieve an internal quantum efficiency (IQE) of 100%. The extremely small energy gap ( \(\:\varDelta\:{E}_{ST}\) ) between the lowest singlet state (S 1 ) and the triplet state (T 1 ) of the excited state can increase the reverse intersystem crossing rate constant ( \(\:{k}_{RISC}\) ) from T 1 to S 1 . Integrating the functions of MCL and TADF into a single molecule will provide great opportunities for the multifunctional applications of organic emitters. In 2015, Chi et al. reported a single-molecule TADF white-emitting molecule that exhibited obvious MCL behavior 12 . In 2017, Swager and his colleagues introduced a series of TADF emitters, which showed significant two-color MCL responses 13 . In the same year, Takeda and his colleagues developed the first molecule with both TADF and multi-chromic MCL 14 . Recently, Wang and his colleagues reported a novel MCL-active TADF material based on changes in packing arrangements 15 . However, despite these advances, due to the lack of a systematic molecular design, the research on efficient TADF with multicolor MCL materials is still in its infancy. The 2,3,5,6-tetrakis(carbazol-9-yl)-1,4-dicyanobenzene (4CzTPN) exemplifies a thermally activated delayed fluorescence (TADF) molecule characterized by a twisted donor-acceptor (D-A) molecular architecture 6 , 16 . Within this structure, carbazole units function as electron donors while the dicyanobenzene moiety serves as the electron acceptor (Fig. 1 ). In this work, we explored the mechano-responsive luminescence characteristics of 4CzTPN with in situ high-pressure photoluminescence (PL), time-resolved PL measurements, UV-vis spectra and infrared spectra measurements. In situ steady state PL data show that the PL emission of 4CzTPN exhibits red-shift under high pressure. While PL emission of 4CzTPN exhibits blue-shift upon mechanical grinding. And time-resolved PL measurements data display that the average short PL lifetime decreases when the pressure is from 0 GPa to 10.0 GPa. Moreover, average long PL lifetime disappears when the pressure is beyond 3.0 GPa. In order to further analyze the properties of mechano-responsive luminescence characteristics of 4CzTPN, the powerful infrared spectra measurements are applied to investigate structural change. This work gives deep insight into the interesting mechanoresponsive behavior of 4CzTPN crystals from the structural point of view. Results and discussion Under ambient conditions, 4CzTPN crystals presented a bright yellow emission with the maximum wavelength (λ em ) of 580 nm, which was attributed to the S 1 -S 0 transition 6 . Upon compression, the PL intensity continuously decreased. With the change of emission intensity, the PL maximum showed a remarkable red-shift of approximately 97 nm, reaching up to 10.6 GPa (Fig. 2 a). The pressure coefficient of emission wavelengths was 9.4 nm GPa − 1 , which could be represented by the slope of linear fitting (Fig. 2 b). The red-shift of emission wavelength led to the reduction of S 1 energy level. The changes of S 1 energy level and T 1 energy level were the main reasons for the complex evolution of the PL lifetime. The fluorescence photographs exhibited the pressure-dependent color change process of the 4CzTPN crystal. Emission color changed through yellow to red step-by-step (Fig. 2 a). After releasing pressure, the PL spectra reverted to the original wavelength, providing unambiguous evidence of the reversible piezo-chromic behavior of the material. Figure 2 c showed the UV-visible absorption spectra of 4CzTPN crystal under high pressure. With the increasing pressure, an obvious red shift was observed, which was consistent with the significant red shift of the photoluminescence (PL) spectra. This distinct red shift phenomenon could be directly reflected by the change of the optical color, transitioning from yellow to red and then to black. The red-shift of UV-visible absorption band resulted in the reduction of S 1 energy level. The changes of S 1 energy level would be responsible for the complex evolution of the PL lifetime. More interestingly, after being ground, the PL spectrum exhibited a blue shift phenomenon of approximately 16 nm (Fig. 2 d). The blue shift may be resulted from a phase transition from crystalline state to amorphous state by grinding 17 – 19 . Table 1 The value of delay PL emission lifetime at different pressure. Pressure/GPa 0.0 0.5 1.0 1.5 2.1 3.0 Delay emission lifetime/µs 1.68 1.76 1.78 1.80 1.75 1.63 In order to elucidate the pressure-dependent behavior of PL emission as observed, we conducted measurements of the PL decay curves for 4CzTPN crystals under different pressures (as depicted in Fig. 3 a and Fig. 3 c). The emission decay profiles were modeled using a biexponential function 20 , 21 . Subsequently, the variations in the average lifetime as a function of increasing pressure are illustrated in Fig. 3 b. The average lifetime, referred to as the intensity-weighted lifetime \(\:{\tau\:}_{iw}\) , is calculated according to the formula \(\:{\tau\:}_{iw}=\left(A{\tau\:}_{1}^{2}+B{\tau\:}_{2}^{2}\right)/\left(A{\tau\:}_{1}+B{\tau\:}_{2}\right)\) 20, 22 . Under ambient conditions, there obviously existed two lifetime decay processes: a short PL lifetime of 7.94 ns and a long PL lifetime of 1.68 µs. The long PL lifetime could readily be attributed to the delayed fluorescence. The short PL lifetime was assigned as promoted fluorescence. Upon compression, the average short-lived component decreased sharply (Fig. 3 b). More interesting, the average long-lived component disappeared beyond 3.0 GPa (Table 1 ). The vanishing of delayed fluorescence would be due to the widening of singlet–triplet (S 1 and T 1 ) energy gap \(\:\varDelta\:{E}_{ST}\) 2 3 , 24 . In-situ high-pressure infrared spectroscopy measurements (Fig. 4 ) were carried out to understand the unique PL emission behavior based on the structural aspects. It can be seen that the entire infrared peak shifted to higher frequencies, which would promote the non-radiative process. The bands in the range of 1386 to 1536 cm⁻¹ are the C-H wagging (δ(C-H)) of the carbazole segment of 4CzTPN. Under compression, the wavenumber of the C-H bond showed a blue shift, indicating that as the C-H bond continued to be compressed and shortened, the vibration was enhanced, suggesting stronger molecular interactions. The band at 2237 cm⁻¹ can be identified as the stretching vibration of C ≡ N (ν(C ≡ N)), which is characteristic of the cyano bond 25 . The bands in the range of 3000 to 3100 cm⁻¹ are the C-H stretching vibrations (ν(C-H)) of the carbazole segment 26 . When be compressed, the relative intensity of the infrared absorption peak of ν(C-H) changed. The peak at 3023 cm⁻¹ (marked with an asterisk) gradually became stronger and shifted to a higher wavenumber, taking the dominant position. This indicated that with the increase of pressure, the absorption peak of (ν(C-H) changed due to the emergence of many newly formed intramolecular interactions within the reduced spacing 27 . When the pressure was greater than 3.0 GPa, the style of relative intensity for the infrared absorption peak of ν(C-H) transformed significantly, which would be the reason for the disappearance of delayed fluorescence. After the release of pressure, all the peaks in the infrared spectrum completely returned to their original states, which would be responsible for the of reversibility PL emission wavelength. Conclusion In summary, we find that the 4CzTPN crystal presents distinct luminescent responses to anisotropic grinding and isotropic compression. Grinding of the crystals leads to a phase transition from crystalline state to amorphous state, which would be responsible for the blue-shift of PL emission. In sharp contrast, high-pressure experiments carry out with DAC demonstrates that the yellow fluorescence of the crystals transform into red fluorescence with an emission wavelength (λ em ) of 677 nm under a pressure of 10.6 GPa. The red-shift is due to the decrease in the energy level of the S 1 state. High-pressure time-resolved measurements shows that the short fluorescence lifetime decrease, and the lifetime of delayed fluorescence disappears above 3.0 GPa. Infrared spectra indicate the style of relative intensity for the infrared absorption peak of ν(C-H) transform significantly when the pressure is greater than 3.0 GPa, which would be the cause of the disappearance of delayed fluorescence. This study has expanded the versatility of TADF material. It also indicates that high-pressure treatment is an effective method for controlling the fluorescence lifetime of TADF materials, providing a new approach to improving the performance of TADF-OLEDs. Methods Sample preparation and high-pressure generation 4CzTPN was purchased from Xi’an baolaite Technology Ltd and used as received. A symmetric diamond anvil cell (DAC) was used to generate high pressure. A T301 steel gasket was preindented to a thickness of 40 mm. The sample was loaded into a 150 mm size hole of the gasket. A small ruby ball was placed into the hole for in situ pressure calibration according to the R 1 ruby fluorescence method. Thick CCl 4 (Aldrich) was used as the pressure-transition medium (PTM) in the high-pressure PL, UV-Vis, IR measurement. Optical measurements The 355 nm line of a UV DPSS laser was used for PL measurements (Light & Microvision Industrial Technology Co., Ltd). The optical fiber spectrometer is an Ocean Optics QE65Pro spectrometer. The PL micrographs of the samples were captured using a Canon camera equipped on the light path. Time resolved PL data was collected via Edinburgh FLS1000 photoluminescence spectrometer under the laser excitation at 375 nm. The measured PL decay curves were fitted using double exponential functions. The IR absorption modes were detected by a liquid-nitrogen-cooled detector through a microscope spectrometer of SHMADZU, IRTracer-100. Declarations Competing interests The authors declare no competing interests. Author Contribution Y.G. designed this study. L.L. conducted the experiments. Y.G. performed all data analyses, and organized all figures and tables. Y.G., M.W., and K.W. written the main manuscript. All authors have read and approved the final manuscript. All the authors have approved this manuscript for publication. Acknowledgements This work was supported by the National Natural Science Foundation of China (NSFC) (12304266, 12304262), the Applied Basic Research program of Shanxi Province (202103021223361), Shandong Provincial Natural Science Foundation of China (ZR2024QA156). Data Availability The data that support the fundings of this study are available from the corresponding author upon reasonable request. References Zhang, X., Chi, Z., Zhang, Y., Liu, S. & Xu, J. Recent advances in mechanochromic luminescent metal complexes. J Mater. Chem. C 1 (2013). Yao, Z. Q. et al. A Dual-Stimuli-Responsive Coordination Network Featuring Reversible Wide-Range Luminescence-Tuning Behavior. Angew Chem. Int. Ed. Engl. 58 , 5614–5618 (2019). Shi, Y. et al. Pressure-Induced Emission (PIE) of One-Dimensional Organic Tin Bromide Perovskites. J. 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Mater. 31 , 1808242 (2019). Zobel, J. P., Wernbacher, A. M. & Gonzalez, L. Efficient Reverse Intersystem Crossing in Carbene-Copper-Amide TADF Emitters via an Intermediate Triplet State. Angew Chem. Int. Ed. Engl. 62 , e202217620 (2023). Phan Huu, D. K. A. et al. Thermally Activated Delayed Fluorescence: Polarity, Rigidity, and Disorder in Condensed Phases. J. Am. Chem. Soc. 144 , 15211–15222 (2022). Xie, Z. et al. White-light emission strategy of a single organic compound with aggregation-induced emission and delayed fluorescence properties. Angew Chem. Int. Ed. Engl. 54 , 7181–7184 (2015). Tsujimoto, H. et al. Thermally Activated Delayed Fluorescence and Aggregation Induced Emission with Through-Space Charge Transfer. J. Am. Chem. Soc. 139 , 4894–4900 (2017). Okazaki, M. et al. Thermally activated delayed fluorescent phenothiazine-dibenzo[a,j]phenazine-phenothiazine triads exhibiting tricolor-changing mechanochromic luminescence. Chem. Sci. 8 , 2677–2686 (2017). Zhao, C. et al. Thermally activated delayed fluorescence with dual-emission and pressure-induced bidirectional shifting: cooperative effects of intramolecular and intermolecular energy transfer. Chem. Sci. 14 , 1089–1096 (2023). Ishimatsu, R. et al. Electrogenerated chemiluminescence of donor-acceptor molecules with thermally activated delayed fluorescence. Angew Chem. Int. Ed. Engl. 53 , 6993–6996 (2014). Li, J. et al. Luminogens Based on Cyano-Substituted Anthracene Isomers: Different Molecular Packing and Distinct Piezochromic Properties. Adv Opt. Mater 9 (2021). Nagura, K. et al. Distinct responses to mechanical grinding and hydrostatic pressure in luminescent chromism of tetrathiazolylthiophene. J. Am. Chem. Soc. 135 , 10322–10325 (2013). Lv, Y., Liu, Y., Ye, X., Liu, G. & Tao, X. The effect of mechano-stimuli on the amorphous-to-crystalline transition of mechanochromic luminescent materials. CrystEngComm 17 , 526–531 (2015). Li, Y. et al. Investigations on Average Fluorescence Lifetimes for Visualizing Multi-Exponential Decays. Front. Phys. 8 , 576862 (2020). Engelborghs, A. S. Y. The Correct Use of Average Fluorescence Parameters. Photochem. Photobiol . 67 , 475–486 (1998). Thor, W., Bünzli, J. C. G., Wong, K. L. & Tanner, P. A. Shedding Light on Luminescence Lifetime Measurement and Associated Data Treatment. Adv. Photonics Res. 6 , 2400081 (2024). Eng, J. & Penfold, T. J. Open questions on the photophysics of thermally activated delayed fluorescence. Commun. Chem. 4 , 91 (2021). Noda, H., Nakanotani, H. & Adachi, C. Excited state engineering for efficient reverse intersystem crossing. Sci. Adv. 4 , eaao6910 (2018). Liu, J., Feng, R., Zhou, L., Gai, F. & Zhang, W. Photoenhancement of the C ≡ N Stretching Vibration Intensity of Aromatic Nitriles. J. Phys. Chem. Lett. 13 , 9745–9751 (2022). Gu, Y. et al. Pressure-Induced Emission Enhancement of Carbazole: The Restriction of Intramolecular Vibration. J. Phys. Chem. Lett. 8 , 4191–4196 (2017). Wang, Y. et al. Pressure-Engineered Through-Space Conjugation for Precise Control of Clusteroluminescence. Angew Chem. Int. Ed. Engl. 64 , e202420502 (2025). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 16 Oct, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 11 Jul, 2025 Reviews received at journal 10 Jul, 2025 Reviewers agreed at journal 21 Jun, 2025 Reviews received at journal 20 Jun, 2025 Reviewers agreed at journal 16 Jun, 2025 Reviews received at journal 15 Jun, 2025 Reviewers agreed at journal 15 Jun, 2025 Reviewers invited by journal 15 Jun, 2025 Editor assigned by journal 11 Jun, 2025 Editor invited by journal 11 Jun, 2025 Submission checks completed at journal 11 Jun, 2025 First submitted to journal 01 Jun, 2025 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. 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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-6794720","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":471920727,"identity":"53ec9e40-5ed1-4637-bb0c-627e48a10d36","order_by":0,"name":"Yarong Gu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwUlEQVRIiWNgGAWjYLCChAobHn5m5sMPiNfy4EyanGQ7W5oB0ToYH7YdNjY4z6MgQZRy+Ygcsw+JbYcTNx/mYTBgqLGJJqjF8EaO8YyEc+mJ2w7zHnjAcCwtt4Gglhk5xgwJZdZALXwJBowNh4nVwsacuLmZx0CCKC3yEiAtbc7GBszEajHgeVbMkAAMZInDwEBOIMYv8u3Jmxl/gKKy//DhBx9qbIiw5QAHUgQmEFIOtqWB/QEx6kbBKBgFo2AkAwB8tD9+aB4QLAAAAABJRU5ErkJggg==","orcid":"","institution":"Xinzhou Normal University","correspondingAuthor":true,"prefix":"","firstName":"Yarong","middleName":"","lastName":"Gu","suffix":""},{"id":471920728,"identity":"bfd230f6-25e2-47a2-9abd-7c2243461ea0","order_by":1,"name":"Long Li","email":"","orcid":"","institution":"Liaocheng University","correspondingAuthor":false,"prefix":"","firstName":"Long","middleName":"","lastName":"Li","suffix":""},{"id":471920729,"identity":"e6f3ffcd-92c7-4f1a-9ff6-5066fcc6c585","order_by":2,"name":"Min Wu","email":"","orcid":"","institution":"Liaocheng University","correspondingAuthor":false,"prefix":"","firstName":"Min","middleName":"","lastName":"Wu","suffix":""},{"id":471920730,"identity":"087b9f7f-2b5d-42e6-8660-2e1d06ac9e4f","order_by":3,"name":"Kai Wang","email":"","orcid":"","institution":"Liaocheng University","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2025-06-01 08:53:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6794720/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6794720/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-20002-z","type":"published","date":"2025-10-16T15:57:41+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":84914192,"identity":"3313980a-4c51-4c2d-b20f-2687cc8615ab","added_by":"auto","created_at":"2025-06-18 17:50:56","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":9378,"visible":true,"origin":"","legend":"\u003cp\u003eChemical structure of 4CzTPN.\u003c/p\u003e","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6794720/v1/14d3001cbe8ebab8d841e3ae.png"},{"id":84913927,"identity":"5ab50c2c-616b-49a8-9823-ad269d429e16","added_by":"auto","created_at":"2025-06-18 17:42:56","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":47468,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Pressure-dependent PL emissions of 4CzPN. Insets illustrate the corresponding PL micrographs with increasing pressure. (b) Pressure-dependent emission wavelengths of 4CzPN. Black lines represent linear fittings of the data to achieve pressure coefficients of emission wavelengths. (c) UV-Vis spectra of 4CzPN under high pressure. Insets illustrate the corresponding sample micrographs with increasing pressure. (d) PL emissions of 4CzPN upon grinding.\u003c/p\u003e","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6794720/v1/0614542cc93ad075f12259bc.png"},{"id":84913930,"identity":"fb1dc1d9-0c93-4650-afff-0303a13b462a","added_by":"auto","created_at":"2025-06-18 17:42:56","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":51667,"visible":true,"origin":"","legend":"\u003cp\u003e(a,c) High pressure PL decay curves of the 4CzTPN crystals in the time range of 0-100 ns and 0-2700 ns. (b) The change of average short PL lifetime at different pressure.\u003c/p\u003e","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6794720/v1/42de9ed4a3b00378c5762c88.png"},{"id":84913932,"identity":"b83b3596-01ff-4464-a716-cf0a22ab5d2d","added_by":"auto","created_at":"2025-06-18 17:42:56","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":86305,"visible":true,"origin":"","legend":"\u003cp\u003eHigh Pressure IR spectra of 4CzTPN in the wavenumber region of 500 cm\u003csup\u003e-1\u003c/sup\u003e-3500 cm\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6794720/v1/10cc222137a02eda3a2ebf63.png"},{"id":93956745,"identity":"c1d087f9-367a-4c4e-9be1-f06fc55a54f9","added_by":"auto","created_at":"2025-10-20 16:12:05","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":702387,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6794720/v1/63a2807d-c83a-47b6-8280-ddf6f94aceb5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Distinct mechano- and piezochromic behaviors of thermally activated delayed fluorescence（4CzTPN）crystal","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMechanochromic luminescence (MCL) molecules, as a new type of smart material, have been widely applied in fields such as sensors, optoelectronic devices, and anti-counterfeiting inks, which has attracted extensive attention\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Under external force stimuli, such as pressing, grinding, friction, and shearing, these materials can exhibit unique luminescence changes. In the past few years, significant progress has been made in MCL materials. At the same time, metal-free modern luminescent organic materials with thermally activated delayed fluorescence (TADF) behavior have become one of the most attractive luminescent materials in the field of organic light-emitting diodes (OLEDs)\u003csup\u003e\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Such materials can achieve an internal quantum efficiency (IQE) of 100%. The extremely small energy gap (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:{E}_{ST}\\)\u003c/span\u003e\u003c/span\u003e) between the lowest singlet state (S\u003csub\u003e1\u003c/sub\u003e) and the triplet state (T\u003csub\u003e1\u003c/sub\u003e) of the excited state can increase the reverse intersystem crossing rate constant (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{k}_{RISC}\\)\u003c/span\u003e\u003c/span\u003e) from T\u003csub\u003e1\u003c/sub\u003e to S\u003csub\u003e1\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eIntegrating the functions of MCL and TADF into a single molecule will provide great opportunities for the multifunctional applications of organic emitters. In 2015, Chi et al. reported a single-molecule TADF white-emitting molecule that exhibited obvious MCL behavior\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. In 2017, Swager and his colleagues introduced a series of TADF emitters, which showed significant two-color MCL responses\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. In the same year, Takeda and his colleagues developed the first molecule with both TADF and multi-chromic MCL\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Recently, Wang and his colleagues reported a novel MCL-active TADF material based on changes in packing arrangements\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. However, despite these advances, due to the lack of a systematic molecular design, the research on efficient TADF with multicolor MCL materials is still in its infancy.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe 2,3,5,6-tetrakis(carbazol-9-yl)-1,4-dicyanobenzene (4CzTPN) exemplifies a thermally activated delayed fluorescence (TADF) molecule characterized by a twisted donor-acceptor (D-A) molecular architecture\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Within this structure, carbazole units function as electron donors while the dicyanobenzene moiety serves as the electron acceptor (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In this work, we explored the mechano-responsive luminescence characteristics of 4CzTPN with in situ high-pressure photoluminescence (PL), time-resolved PL measurements, UV-vis spectra and infrared spectra measurements. In situ steady state PL data show that the PL emission of 4CzTPN exhibits red-shift under high pressure. While PL emission of 4CzTPN exhibits blue-shift upon mechanical grinding. And time-resolved PL measurements data display that the average short PL lifetime decreases when the pressure is from 0 GPa to 10.0 GPa. Moreover, average long PL lifetime disappears when the pressure is beyond 3.0 GPa. In order to further analyze the properties of mechano-responsive luminescence characteristics of 4CzTPN, the powerful infrared spectra measurements are applied to investigate structural change. This work gives deep insight into the interesting mechanoresponsive behavior of 4CzTPN crystals from the structural point of view.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e \u003c/p\u003e \u003cp\u003eUnder ambient conditions, 4CzTPN crystals presented a bright yellow emission with the maximum wavelength (λ\u003csub\u003eem\u003c/sub\u003e) of 580 nm, which was attributed to the S\u003csub\u003e1\u003c/sub\u003e-S\u003csub\u003e0\u003c/sub\u003e transition\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Upon compression, the PL intensity continuously decreased. With the change of emission intensity, the PL maximum showed a remarkable red-shift of approximately 97 nm, reaching up to 10.6 GPa (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The pressure coefficient of emission wavelengths was 9.4 nm GPa\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which could be represented by the slope of linear fitting (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). The red-shift of emission wavelength led to the reduction of S\u003csub\u003e1\u003c/sub\u003e energy level. The changes of S\u003csub\u003e1\u003c/sub\u003e energy level and T\u003csub\u003e1\u003c/sub\u003e energy level were the main reasons for the complex evolution of the PL lifetime. The fluorescence photographs exhibited the pressure-dependent color change process of the 4CzTPN crystal. Emission color changed through yellow to red step-by-step (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). After releasing pressure, the PL spectra reverted to the original wavelength, providing unambiguous evidence of the reversible piezo-chromic behavior of the material. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec showed the UV-visible absorption spectra of 4CzTPN crystal under high pressure. With the increasing pressure, an obvious red shift was observed, which was consistent with the significant red shift of the photoluminescence (PL) spectra. This distinct red shift phenomenon could be directly reflected by the change of the optical color, transitioning from yellow to red and then to black. The red-shift of UV-visible absorption band resulted in the reduction of S\u003csub\u003e1\u003c/sub\u003e energy level. The changes of S\u003csub\u003e1\u003c/sub\u003e energy level would be responsible for the complex evolution of the PL lifetime. More interestingly, after being ground, the PL spectrum exhibited a blue shift phenomenon of approximately 16 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). The blue shift may be resulted from a phase transition from crystalline state to amorphous state by grinding\u003csup\u003e\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe value of delay PL emission lifetime at different pressure.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePressure/GPa\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDelay emission lifetime/\u0026micro;s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.63\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn order to elucidate the pressure-dependent behavior of PL emission as observed, we conducted measurements of the PL decay curves for 4CzTPN crystals under different pressures (as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). The emission decay profiles were modeled using a biexponential function\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Subsequently, the variations in the average lifetime as a function of increasing pressure are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb. The average lifetime, referred to as the intensity-weighted lifetime \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{iw}\\)\u003c/span\u003e\u003c/span\u003e, is calculated according to the formula \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{iw}=\\left(A{\\tau\\:}_{1}^{2}+B{\\tau\\:}_{2}^{2}\\right)/\\left(A{\\tau\\:}_{1}+B{\\tau\\:}_{2}\\right)\\)\u003c/span\u003e\u003c/span\u003e\u003csup\u003e20,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Under ambient conditions, there obviously existed two lifetime decay processes: a short PL lifetime of 7.94 ns and a long PL lifetime of 1.68 \u0026micro;s. The long PL lifetime could readily be attributed to the delayed fluorescence. The short PL lifetime was assigned as promoted fluorescence. Upon compression, the average short-lived component decreased sharply (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). More interesting, the average long-lived component disappeared beyond 3.0 GPa (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The vanishing of delayed fluorescence would be due to the widening of singlet\u0026ndash;triplet (S\u003csub\u003e1\u003c/sub\u003e and T\u003csub\u003e1\u003c/sub\u003e) energy gap \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:{E}_{ST}\\)\u003c/span\u003e\u003c/span\u003e\u003csup\u003e2\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn-situ high-pressure infrared spectroscopy measurements (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) were carried out to understand the unique PL emission behavior based on the structural aspects. It can be seen that the entire infrared peak shifted to higher frequencies, which would promote the non-radiative process. The bands in the range of 1386 to 1536 cm⁻\u0026sup1; are the C-H wagging (δ(C-H)) of the carbazole segment of 4CzTPN. Under compression, the wavenumber of the C-H bond showed a blue shift, indicating that as the C-H bond continued to be compressed and shortened, the vibration was enhanced, suggesting stronger molecular interactions. The band at 2237 cm⁻\u0026sup1; can be identified as the stretching vibration of C\u0026thinsp;\u0026equiv;\u0026thinsp;N (ν(C\u0026thinsp;\u0026equiv;\u0026thinsp;N)), which is characteristic of the cyano bond\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The bands in the range of 3000 to 3100 cm⁻\u0026sup1; are the C-H stretching vibrations (ν(C-H)) of the carbazole segment\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. When be compressed, the relative intensity of the infrared absorption peak of ν(C-H) changed. The peak at 3023 cm⁻\u0026sup1; (marked with an asterisk) gradually became stronger and shifted to a higher wavenumber, taking the dominant position. This indicated that with the increase of pressure, the absorption peak of (ν(C-H) changed due to the emergence of many newly formed intramolecular interactions within the reduced spacing\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. When the pressure was greater than 3.0 GPa, the style of relative intensity for the infrared absorption peak of ν(C-H) transformed significantly, which would be the reason for the disappearance of delayed fluorescence. After the release of pressure, all the peaks in the infrared spectrum completely returned to their original states, which would be responsible for the of reversibility PL emission wavelength.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, we find that the 4CzTPN crystal presents distinct luminescent responses to anisotropic grinding and isotropic compression. Grinding of the crystals leads to a phase transition from crystalline state to amorphous state, which would be responsible for the blue-shift of PL emission. In sharp contrast, high-pressure experiments carry out with DAC demonstrates that the yellow fluorescence of the crystals transform into red fluorescence with an emission wavelength (λ\u003csub\u003eem\u003c/sub\u003e) of 677 nm under a pressure of 10.6 GPa. The red-shift is due to the decrease in the energy level of the S\u003csub\u003e1\u003c/sub\u003e state. High-pressure time-resolved measurements shows that the short fluorescence lifetime decrease, and the lifetime of delayed fluorescence disappears above 3.0 GPa. Infrared spectra indicate the style of relative intensity for the infrared absorption peak of ν(C-H) transform significantly when the pressure is greater than 3.0 GPa, which would be the cause of the disappearance of delayed fluorescence. This study has expanded the versatility of TADF material. It also indicates that high-pressure treatment is an effective method for controlling the fluorescence lifetime of TADF materials, providing a new approach to improving the performance of TADF-OLEDs.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eSample preparation and high-pressure generation\u003c/h2\u003e \u003cp\u003e4CzTPN was purchased from Xi\u0026rsquo;an baolaite Technology Ltd and used as received. A symmetric diamond anvil cell (DAC) was used to generate high pressure. A T301 steel gasket was preindented to a thickness of 40 mm. The sample was loaded into a 150 mm size hole of the gasket. A small ruby ball was placed into the hole for in situ pressure calibration according to the R\u003csub\u003e1\u003c/sub\u003e ruby fluorescence method. Thick CCl\u003csub\u003e4\u003c/sub\u003e (Aldrich) was used as the pressure-transition medium (PTM) in the high-pressure PL, UV-Vis, IR measurement.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eOptical measurements\u003c/h3\u003e\n\u003cp\u003eThe 355 nm line of a UV DPSS laser was used for PL measurements (Light \u0026amp; Microvision Industrial Technology Co., Ltd). The optical fiber spectrometer is an Ocean Optics QE65Pro spectrometer. The PL micrographs of the samples were captured using a Canon camera equipped on the light path. Time resolved PL data was collected via Edinburgh FLS1000 photoluminescence spectrometer under the laser excitation at 375 nm. The measured PL decay curves were fitted using double exponential functions. The IR absorption modes were detected by a liquid-nitrogen-cooled detector through a microscope spectrometer of SHMADZU, IRTracer-100.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eY.G. designed this study. L.L. conducted the experiments. Y.G. performed all data analyses, and organized all figures and tables. Y.G., M.W., and K.W. written the main manuscript. All authors have read and approved the final manuscript. All the authors have approved this manuscript for publication.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis work was supported by the National Natural Science Foundation of China (NSFC) (12304266, 12304262), the Applied Basic Research program of Shanxi Province (202103021223361), Shandong Provincial Natural Science Foundation of China (ZR2024QA156).\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data that support the fundings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eZhang, X., Chi, Z., Zhang, Y., Liu, S. \u0026amp; Xu, J. Recent advances in mechanochromic luminescent metal complexes. \u003cem\u003eJ Mater. Chem. C\u003c/em\u003e 1 (2013).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYao, Z. Q. et al. 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Engl.\u003c/em\u003e \u003cb\u003e64\u003c/b\u003e, e202420502 (2025).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Thermally activated delayed fluorescence materials, Solid state fluorescence lifetime, High pressure, IR spectra, OLED","lastPublishedDoi":"10.21203/rs.3.rs-6794720/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6794720/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIncorporating mechano-luminescence (MCL) into thermally activated delayed fluorescence (TADF) molecules represents a promising strategy for developing multifunctional mechanoluminescent materials. However, the controllable utilization of the versatile properties inherent in TADF molecules remains challenging due to the inherent difficulties in system design. Herein, we investigate the pressure modulation of the photophysical properties of 2,3,5,6-tetrakis(carbazol-9-yl)-1,4-dicyanobenzene (4CzTPN), a representative TADF emitter, through in situ high-pressure photoluminescence (PL), time-resolved PL, UV-visible spectra and infrared spectroscopy. The different mechanisms of a blue shift by grinding crystals and of a red shift under hydrostatic pressure are fully investigated. High-pressure time-resolved measurements show that the short fluorescence lifetime decreases and the lifetime of delayed fluorescence disappears beyond 3.0 GPa. Infrared spectra indicate the style of relative intensity for the infrared absorption peak of ν(C-H) transform significantly when the pressure is greater than 3.0 GPa, which would be the cause of the disappearance of delayed fluorescence. This study enriches the insights into mechanochromic and multifunctional materials.\u003c/p\u003e","manuscriptTitle":"Distinct mechano- and piezochromic behaviors of thermally activated delayed fluorescence（4CzTPN）crystal","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-18 17:42:51","doi":"10.21203/rs.3.rs-6794720/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-11T09:16:56+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-11T03:56:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"57672354050440980618413536153756281417","date":"2025-06-22T03:20:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-20T12:55:39+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"280307353813443066304808168415719244933","date":"2025-06-16T10:54:40+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-15T13:33:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"326037245309241992306216939902148805032","date":"2025-06-15T06:23:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-15T04:11:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-11T08:49:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-06-11T08:29:39+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-11T06:29:54+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-06-01T08:50:09+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"068a1a84-0b72-44c5-baf8-8fffe97a0e18","owner":[],"postedDate":"June 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":50113671,"name":"Physical sciences/Chemistry/Materials chemistry"},{"id":50113672,"name":"Physical sciences/Chemistry/Photochemistry"},{"id":50113673,"name":"Physical sciences/Chemistry/Physical chemistry"}],"tags":[],"updatedAt":"2025-10-20T16:08:57+00:00","versionOfRecord":{"articleIdentity":"rs-6794720","link":"https://doi.org/10.1038/s41598-025-20002-z","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-10-16 15:57:41","publishedOnDateReadable":"October 16th, 2025"},"versionCreatedAt":"2025-06-18 17:42:51","video":"","vorDoi":"10.1038/s41598-025-20002-z","vorDoiUrl":"https://doi.org/10.1038/s41598-025-20002-z","workflowStages":[]},"version":"v1","identity":"rs-6794720","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6794720","identity":"rs-6794720","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}