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Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se) 2 Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment
Author(s) -
Kim JooHyun,
Kim Min Kyu,
Gadisa Abay,
Stuard Samuel J.,
Nahid Masrur Morshed,
Kwon Soyeong,
Bae Soohyun,
Kim Byoungwoo,
Park Gi Soon,
Won Da Hye,
Lee Dong Ki,
Kim DongWook,
Shin Tae Joo,
Do Young Rag,
Kim Jihyun,
Choi Won Jun,
Ade Harald,
Min Byoung Koun
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.202003865
Subject(s) - copper indium gallium selenide solar cells , materials science , band gap , energy conversion efficiency , photocurrent , photovoltaic system , solar cell , optoelectronics , grain boundary , nanotechnology , engineering physics , microstructure , electrical engineering , metallurgy , engineering
Solution‐processed Cu(In,Ga)(S,Se) 2 (CIGS) has a great potential for the production of large‐area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum‐processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region. Careful engineering of the bandgap grading structure also results in an enlarged space charge region, which is favorable for electron–hole separation and efficient charge carrier collection. Besides, this device processing approach has led to a linearly increasing electron diffusion length and carrier lifetime with increasing the grain size of the CIGS film, which is a critical achievement for enhancing photocurrent yield. Overall, 15% of power conversion efficiency is achieved in solar cells processed from environmentally benign solutions. This approach offers critical insights for precise device design and processing rules for solution‐processed CIGS solar cells.