DMF‐Based Large‐Grain Spanning Cu<sub>2</sub>ZnSn(S<i><sub>x</sub></i>,Se<sub>1‐</sub><i><sub>x</sub></i>)<sub>4</sub> Device with a PCE of 11.76%
Yubo Cui, Mengyang Wang, Peizhe Dong, Shuangshuang Zhang, Junjie Fu, Libo Fan, Chaoliang Zhao, Sixin Wu, Zhi Zheng
Abstract
Abstract A main concern of the promising DMF‐based Cu 2 ZnSn(S x ,Se 1‐ x ) 4 (CZTSSe) solar cells lies in the absence of a large‐grain spanning structure, which is a key factor for high open‐circuit voltage ( V oc ) and power conversion efficiency (PCE). A new strategy to achieve CZTSSe large‐grain spanning monolayer is proposed, by taking advantage of the synergistic optimization with a Cu 2+ plus Sn 2+ redox system and pre‐annealing temperatures. A series of structural, morphological, electrical, and photoelectric characterizations are employed to study the effects of the pre‐annealing temperatures on absorber qualities, and an optimized temperature of 430 ℃ is determined. The growth mechanism of the large‐grain spanning monolayer and the effect of redox reaction rate are carefully investigated. Three types of absorber growth mechanisms and a concept of critical temperature are proposed. The devices based on this large‐grain spanning monolayer suppress the recombination of carriers at crystal boundaries and interfaces. The champion device exhibits a high V oc (>500 mV) and PCE of 11.76%, which are both the maximum values among DMF‐based solar cells at the current stage.