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

The temperature-dependent (25-300 degrees 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 [Zn-Cu + V-Cu] 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 [2Zn(Cu) + Zn-Sn] increases with increasing temperature and Zn content. The observations further reveal that Zn concentration has less impact on V-Cu formation; therefore, above the optimum Cu-poor and Zn-rich conditions, Zn-Cu 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 approximate to 11.0% with open-circuit voltage of 478 mV, short-circuit current of 35.51 mA cm(-2), and fill factor of 64%, respectively.