A comprehensive material study of CdSeTe films deposited with differing selenium compositions

•CdSeTe films deposited by sublimation have reduced Se content compared to source.•Crystallinity, photoluminescence, and morphology are affected by substrate temperature.•Source material is not stable, results in varying film composition/deposition rate. The addition of selenium into CdTe to create...

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Bibliographic Details
Published in:Thin solid films 2023-03, Vol.768 (C), p.139684, Article 139684
Main Authors: Danielson, Adam, Reich, Carey, Drayton, Jennifer, Bothwell, Alexandra, Shimpi, Tushar, Sites, James, Sampath, Walajabad
Format: Article
Language:English
Subjects:
Cadmium selenide telluride
Cadmium telluride
Close-space sublimation
Photoluminescence
Photovoltaics
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Summary:•CdSeTe films deposited by sublimation have reduced Se content compared to source.•Crystallinity, photoluminescence, and morphology are affected by substrate temperature.•Source material is not stable, results in varying film composition/deposition rate. The addition of selenium into CdTe to create the ternary alloy CdSeTe has been one of the most impactful advancements to CdTe-based photovoltaics in the last decade. CdSeTe/CdTe bilayer device structures have enabled a gain in short-circuit current due to the narrower bandgap of the alloy, with minimal to no loss in voltage. Intensity of photoluminescence and time-resolved photoluminescence measurements suggest this is due to an increase in carrier lifetime and concomitant greater fraction of radiative vs non-radiative recombination events which allows for a reduction in the voltage deficit. Here, we study the properties of as-deposited and CdCl2-treated CdSeTe films deposited by close-space sublimation under varying conditions from CdSeTe source charges with both 20 and 40 mol% CdSe. We find that the selenium content in the deposited films are substantially reduced from that of the source material. Additionally, deposition temperature, particularly that of the substrate, considerably affects the grain size, crystallinity, and photoluminescence of the material, illustrating the importance of source material selection and process optimization. Finally, we present evidence that the source material, and therefore the properties of the deposited films, change over time as the source material is used.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2023.139684