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DOE OSTI · 2500791

Development of High-Quality, Very Large-Grained Cd(Se,Te) Thin Films for CdTe Solar Modules (Final Technical Report)

Duenow, Joel [National Renewable Energy Laboratory (NREL), Golden, CO (United States)]·Albin, David [National Renewable Energy Laboratory (NREL), Golden, CO (United States)]
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Abstract

TCF-21-25048 is a one-year project to quantify the potential attributes of recent NREL inventions where CdTe devices with grain sizes exceeding 100's of microns in lateral dimension can be fabricated using a novel seeded-epitaxial process. A CdSe0.1Te0.9 film is evaporated on commercially available transparent conducting oxide (TCO) where the latter surface roughness (Ra) has been reduced to < 1-nm. After NREL's colossal grain growth (CGG) process, the grain size of this "seed" layer is increased to 100-1000 um. CdTe is then deposited epitaxially resulting in a large-grain CdTe device structure without use of CdCl2. As of this report, we have: Demonstrated the feasibility of using Tec-15 substrates after surface roughness (Ra) reduction (nexTC); Developed reproducible CGG processes for this commercially available substrate; Developed a close-spaced sublimation (CSS) process for CdTe epitaxy using these substrates; Demonstrated that large-grain CdTe films have less sub-band (band tail) absorption than conventional, small-grain CdTe; Demonstrated that large-grain CdTe films (no CdCl2) have carrier lifetimes up to 1.5 ns; Demonstrated that carrier lifetimes in epi-CdTe films (no CdCl2) have comparable lifetimes when compared to the best pX-CdTe films (FSLR) treated with CdCl2; Started making large-grain CdTe devices using CGG templates and epitaxially deposited CdTe.

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Duenow, Joel [National Renewable Energy Laboratory (NREL), Golden, CO (United States)], Albin, David [National Renewable Energy Laboratory (NREL), Golden, CO (United States)]. 2025-01-09. Development of High-Quality, Very Large-Grained Cd(Se,Te) Thin Films for CdTe Solar Modules (Final Technical Report). https://doi.org/10.2172/2500791

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