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Large open‐circuit voltage boosting of pure sulfide chalcopyrite Cu(In,Ga)S 2 prepared using Cu‐deficient metal precursors
Author(s) -
Kim Shinho,
Nagai Takehiko,
Tampo Hitoshi,
Ishizuka Shogo,
Shibata Hajime
Publication year - 2020
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.3277
Subject(s) - copper indium gallium selenide solar cells , chalcopyrite , photoluminescence , open circuit voltage , sulfide , materials science , copper , metal , analytical chemistry (journal) , chemistry , optoelectronics , solar cell , metallurgy , voltage , electrical engineering , chromatography , engineering
We performed a comparative study to find out the reasons why it is necessary to prepare the pure sulfide chalcopyrite, Cu(InGa)S 2 (CIGS) under a Cu‐deficient condition to improve solar cell performance. It has been shown that CIGS that was grown under Cu‐deficient condition exhibits large open‐circuit voltage ( V OC ) boosting compared with that the one grown under Cu‐excess condition. Thus, CIGS were prepared from Cu‐excess and Cu‐deficient metal precursor (MP) and characterized concerning the origins of the different V OC . We observed that CIGS prepared using Cu‐excess MP suffered large recombination at buffer/CIGS interface and in bulk, which resulted in serious limitation of the V OC . On the other hand, CIGS prepared from Cu‐deficient MP exhibited largely improved V OC with reduced recombination. We conducted defect analysis using the photoluminescence (PL) method, and CIGS prepared using Cu‐excess MP exhibited strong deep emissions. However, CIGS prepared from Cu‐deficient MP exhibited PL emission characteristics without deep level transition. This implies that a large number of deep level defects exist in the CIGS prepared using Cu‐excess MP, and this might be the reason for the large recombination limiting V OC of the device. Finally, we also present the reason for deep levels in the CIGS prepared using Cu‐excess MP.