Numerical Investigation of Copper Zinc Tin Sulphide Based Solar Cell with Non‐Toxic Zn (O, S) Buffer Layer

Abstract

Zinc oxide sulphide Zn (O, S) buffer layer has attracted enormous attention due to its composition of non‐toxic, low cost, and earth abundant elements, unlike cadmium sulphide (CdS) used in copper zinc tin sulphide (CZTS) solar cells. Zn (O, S) possesses a direct optical bandgap that's adjustable between 2.7 and 3.6 eV related to the mole fraction , making it a potential candidate as a buffer layer with CZTS based solar cells. In this work, the Zn (O, S)/CZTS‐based solar cell structure is numerically studied and compared with CdS/CZTS. The existence of defects and traps along the layers and interfaces is taken in consideration. To achieve optimal results, this research has focused on; effects of the element composition (x = S/(S + O)) ratio of Zn (O, S) buffer layer, the addition of a back surface field (BSF) layer, the influence of Zn (O, S)/CZTS and CdS/CZTS interfaces defect density, varying thicknesses and doping concentrations of the layers (absorber, buffer, BSF) on open‐circuit voltage (Voc), short‐circuit density (Jsc), fill factor (FF), and power conversion efficiency. Findings illustrate that the highest conversion efficiency of the Zn (O, S)/CZTS solar cell reached 14.65% with Voc = 0.9972 V, Jsc = 18.37 mA cm−2 and FF = 79.96% which is better than the CdS/CZTS structure.