Over 11% Efficient CuGaSe<sub>2</sub> Solar Cells Without Using KCN Treatment
Junbo Gong, Duoqi Gao, Zengyang Ma, Xuke Yang, Junjun Zhang, Xinxing Liu, Chao Chen, Jiang Tang, Bo Da, Jianmin Li, Guojia Fang, Xudong Xiao
Abstract
CuGaSe 2 (CGS) has a bandgap energy of 1.68 eV and is theoretically very suitable to be in tandem with silicon or Cu(In,Ga)Se 2 solar cells. However, due to the high quantity of surface defects, high‐performance CGS usually relies on a KCN surface treatment, which is a high‐toxic process and restricts its further development. Herein, by reducing the exposure time to air of the CGS layer as far as possible and developing a new absorber growth procedure to reduce the surface Cu x Se generation, grain size is successfully increased and interface recombination is reduced without the use of KCN. Combined with a simple annealing process, the defect concentration is successfully decreased and the depletion width is broadened dramatically and the power conversion efficiency is promoted to 11.05% without any traditionally used KCN treatment. This work provides a nontoxic and low‐pollution way to fabricate high‐efficient CGS solar cells.