Photo-activated Charge Transport and Unified Mechanism of Self- Trapped Excitons in Cs₂NaInCl₆ Double Perovskite

Photo-activated Charge Transport and Unified Mechanism of Self- Trapped Excitons in Cs₂NaInCl₆ Double Perovskite | 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 Photo-activated Charge Transport and Unified Mechanism of Self- Trapped Excitons in Cs₂NaInCl₆ Double Perovskite Fahad K. Alshammari, Abdullah A. Alatawi, Achref Jebnouni, Amjad Salamah Aljaloud, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9118340/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract On account of their environmentally-benign composition and structural stability, lead-free halide double perovskites are known for being good substitutes for Pb-based materials. This paper includes a detailed examination of the electrical, optical and structural properties of Cs₂NaInCl₆. It also shows unified photo-physical properties and a charge-transport mechanism controlled by innate self-trapped excitons (STEs). An excellent thermal stability reaching 620°C is confirmed through thermogravimetric analysis while a highly crystalline cubic \(Fm\stackrel{-}{3}m\) phase is demonstrated by X-ray diffraction. Optical absorption, however, provides not only a low Urbach energy (0.31 eV) which confirms minimal disorder but also a wide direct bandgap (4.81 eV). A broad intrinsic blue emission which originates from STEs and a reduced electron–phonon coupling at low temperatures are revealed through temperature-dependent and steady-state photoluminescence measurements. A multi-step relaxation pathway that includes the formation of long-lived localized states, lattice relaxation and ultrafast exciton self-trapping is demonstrated using transient absorption spectroscopy and time-resolved PL. It is proven that Illumination activates persistent photocarriers, improves polarization and reduces the bulk resistance considerably by means of dielectric analysis, electric-modulus modeling and impedance spectroscopy. A strong voltage-independent photoconductive gain reaching three orders of magnitude is further proven by I–V measurements without altering the underlying ohmic transport regime. These results collectively set up a coherent microscopic picture where carrier stabilization, trap filling and STE formation together influence not only the AC/DC transport properties but also the optical emission. Hence, as a lead-free perovskite having strong potential for radiation-detection, dielectric and UV-emitting applications, Cs₂NaInCl₆ seems highly stable, robust and intrinsically-excitonic. Physical sciences/Materials science Physical sciences/Optics and photonics Physical sciences/Physics Lead-free double perovskite Self-trapped excitons (STEs) Exciton–phonon coupling Photoluminescence dynamics Wide bandgap semiconductor AC and DC transport Full Text Additional Declarations No competing interests reported. Supplementary Files SupportingInformation.pdf Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 19 Mar, 2026 Editor invited by journal 18 Mar, 2026 Editor assigned by journal 14 Mar, 2026 Submission checks completed at journal 14 Mar, 2026 First submitted to journal 13 Mar, 2026 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-9118340","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":609804804,"identity":"7234c997-f7d7-4dee-8c2d-301b0eb9b02a","order_by":0,"name":"Fahad K. Alshammari","email":"","orcid":"","institution":"University of Ha'il","correspondingAuthor":false,"prefix":"","firstName":"Fahad","middleName":"K.","lastName":"Alshammari","suffix":""},{"id":609804805,"identity":"32d9cc53-b324-4216-ac43-0294915582b1","order_by":1,"name":"Abdullah A. 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This paper includes a detailed examination of the electrical, optical and structural properties of Cs₂NaInCl₆. It also shows unified photo-physical properties and a charge-transport mechanism controlled by innate self-trapped excitons (STEs). An excellent thermal stability reaching 620\u0026deg;C is confirmed through thermogravimetric analysis while a highly crystalline cubic \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(Fm\\stackrel{-}{3}m\\)\u003c/span\u003e\u003c/span\u003e phase is demonstrated by X-ray diffraction. Optical absorption, however, provides not only a low Urbach energy (0.31 eV) which confirms minimal disorder but also a wide direct bandgap (4.81 eV). A broad intrinsic blue emission which originates from STEs and a reduced electron\u0026ndash;phonon coupling at low temperatures are revealed through temperature-dependent and steady-state photoluminescence measurements. A multi-step relaxation pathway that includes the formation of long-lived localized states, lattice relaxation and ultrafast exciton self-trapping is demonstrated using transient absorption spectroscopy and time-resolved PL. It is proven that Illumination activates persistent photocarriers, improves polarization and reduces the bulk resistance considerably by means of dielectric analysis, electric-modulus modeling and impedance spectroscopy. A strong voltage-independent photoconductive gain reaching three orders of magnitude is further proven by I\u0026ndash;V measurements without altering the underlying ohmic transport regime. These results collectively set up a coherent microscopic picture where carrier stabilization, trap filling and STE formation together influence not only the AC/DC transport properties but also the optical emission. Hence, as a lead-free perovskite having strong potential for radiation-detection, dielectric and UV-emitting applications, Cs₂NaInCl₆ seems highly stable, robust and intrinsically-excitonic.\u003c/p\u003e","manuscriptTitle":"Photo-activated Charge Transport and Unified Mechanism of Self- Trapped Excitons in Cs₂NaInCl₆ Double Perovskite","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-23 22:37:38","doi":"10.21203/rs.3.rs-9118340/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-03-19T05:20:33+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-03-18T10:52:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-14T11:48:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-14T11:48:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-03-13T22:17:14+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":"47f5fe69-ec8c-47a7-b6d3-97e3318afa17","owner":[],"postedDate":"March 23rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":64893897,"name":"Physical sciences/Materials science"},{"id":64893898,"name":"Physical sciences/Optics and photonics"},{"id":64893899,"name":"Physical sciences/Physics"}],"tags":[],"updatedAt":"2026-05-14T05:23:18+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-23 22:37:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9118340","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9118340","identity":"rs-9118340","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}