In Search of Disorder Transitions and Defects Within Cu2ZnSn(S,Se)4‐Based Absorber Layers via Temperature‐Dependent Raman Spectroscopy Technique

Abstract

The temperature‐dependent (25–300 °C) disorder transitions analyzed via Raman spectroscopic technique for the different non‐stoichiometric Cu2ZnSn(S,Se)4 (CZTSSe) thin films are demonstrated. In the thin films prepared with different Zn conditions, i.e., in Zn‐1 (Zn‐poor), the density of the A‐type defect cluster [ZnCu + VCu] increases with temperature; however, it slightly decreases and remains constant for Zn‐rich samples, i.e., Zn‐2 and Zn‐3. At the same time, the density of the B‐type defect cluster [2ZnCu + ZnSn] increases with increasing temperature and Zn content. The observations further reveal that Zn concentration has less impact on VCu formation; therefore, above the optimum Cu‐poor and Zn‐rich conditions, ZnCu shallow donors negatively influence the kesterite device performances. Finally, solar cells based on all the CZTSSe thin‐film samples (Zn‐1, Zn‐2, and Zn‐3) are fabricated in which a device based on Zn‐2 exhibits excellent power conversion efficiency of ≈11.0% with open‐circuit voltage of 478 mV, short‐circuit current of 35.51 mA cm−2, and fill factor of 64%, respectively.