Abstract
Two-step selenization process has been proved to control Cu 2 ZnSn(S,Se) 4 (CZTSSe) crystallization growth, helping to fabricate a homogeneous large-grain structure of CZTSSe absorber. The two-step selenization process is usually composed of the low-temperature nucleation (LT) and high-temperature grain growth reaction (HT) processes. Here, an exploration of optimizing the annealing conditions at each step in the two-step process is reported to obtain the excellent structure of ionic liquid solution based Cu 2 ZnSn(S,Se) 4 absorber, boosting performance of the solar cell. Based on the basic requirement of an absorber candidate for solar cells (the compact films), three effective kinds of two-step process are confirmed (LT400–10&HT540–10, LT400–10&HT550–10, and LT400–10&HT560–10). We further explore the other properties of sample prepared by one-step and these three kinds of two-step process, respectively, and the optimal two-step process can be identified as LT400–10&HT550–10, which also confirms a homogeneous large-grain structure of CZTSSe absorber. Finally, CZTSSe solar cell with the highest efficiency of 9.24% can be achieved, which can be improved 67% than one by one-step annealing process (5.54%). • The detail optimization of annealing conditions at each step in the two-step selenization process is explored. • Homogeneous large-grain structure of Cu 2 ZnSn(S,Se) 4 absorber can be fabricated at the optimal two-step selenization condition. • The best efficiency of corresponding device can be obtained to be 9.24%, increased by 67% compared with one-step process.
Published Version
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