DOE OSTI · 3018327
Radiative Defects in Chloride-Activated CdSe Thin Films
Abstract
Defect recombination limits wide-gap Se-based chalcogenide devices, yet how chloride activation reshapes radiative pathways remains unclear. Here we show that a 40 min CdCl 2 anneal converts evaporated CdSe from porous nanograins into dense micrometer-scale polycrystals and sharpens the optical band edge, reducing the Urbach energy from 85 to 17 meV at 300 K. Combining temperature- and fluence-dependent photoluminescence (PL), time-resolved PL, hyperspectral mapping, and hybrid-DFT, we resolve three emissive channels and identify their mechanisms. The near-edge band is excitonic at low temperature and evolves into free-carrier emission at elevated temperature. A sub-gap band at E g −0.45 eV requires above-gap carriers and thermally quenches with a 0.16 eV activation energy. A broad ∼1.05 eV infrared band is excited by above- and below-gap photons and retains microsecond lifetimes at room temperature; patial mapping links it to edge-rich microstructure. Calculations suggest selenium-vacancy and cadmium-vacancy−chlorine complexes, pointing to routes to suppress defect-related losses in wide-gap chalcogenide devices.
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Abudulimu, Abasi [Univ. of Toledo, OH (United States)] (ORCID:0000000217940993), Wang, Xiaoming [Univ. of Toledo, OH (United States)] (ORCID:0000000254381334), Brau, Tyler [Univ. of Toledo, OH (United States)], Kuliček, Jaroslav [Czech Technical Univ., Prague (Czech Republic)], Wenner, Scott L. [Univ. of Toledo, OH (United States)] (ORCID:0000000323543617), Phillips, Adam B. [Univ. of Toledo, OH (United States)] (ORCID:0000000226755052), Bastola, Ebin [Univ. of Toledo, OH (United States)] (ORCID:0000000241943385), Jamarkattel, Manoj K. [Univ. of Toledo, OH (United States)], Karade, Vijay C. [Univ. of Toledo, OH (United States)], Lamichhane, Kiran [Univ. of Toledo, OH (United States)], Dixit, Aparajita [Univ. of Toledo, OH (United States)], Rezek, Bohuslav [Czech Technical Univ., Prague (Czech Republic)] (ORCID:0000000203784598), Yan, Yanfa [Univ. of Toledo, OH (United States)] (ORCID:0000000339775789), Heben, Michael J. [Univ. of Toledo, OH (United States)] (ORCID:0000000237883471), Ellingson, Randy J. [Univ. of Toledo, OH (United States)] (ORCID:0000000195206586). 2026-01-26. Radiative Defects in Chloride-Activated CdSe Thin Films. https://doi.org/10.1021/acsenergylett.5c03191
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