A study on Cr incorporation to enhance performance of CZTSSe solar cells via optimizing selenization condition

Annealing Cu₂ZnSnS₄ (CZTS) precursor films in selenium atmosphere has been demonstrated to be an available means to enhance the quality of Cu₂ZnSn(S,Se)₄ (CZTSSe) absorber. Therefore, it is important to further explore the selenization conditions during annealing. Herein, Cr-doped CZTSSe absorber was synthesized using solution-processed, and the effects of different selenization conditions on the morphology, structure and photoelectrical performances of Cr-doped CZTSSe thin films were investigated firstly. Research shows that morphology of CCZTSSe films was greatly affected by different selenization conditions. By optimizing the selenization conditions, the crystallinity of CCZTSSe absorber was significantly optimized, and the compactness of the absorber was improved. It was further confirmed that the band gap of CCZTSSe absorber can be adjusted via changing the annealing conditions. The CCZTSSe under the optimum selenization conditions showed a better constituent composition, which further inhibited the harmful defects level of Cu_Zn and [2Cu_Zn + Sn_Zn] in the absorber. Finally, the Cr-doped CZTSSe device at optimum selenidation condition of 520 ℃ for 15 min showed the best conversion efficiency of 5.86 %, in which V_OC is 394 mV and FF is 54.07 %, respectively. A new strategy for high efficiency Cr-doped CZTSSe solar cells was proposed by optimizing selenization conditions.