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

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 x=S/(S+O)$x = \text{S} / \left(\right. \text{S} + \text{O} \left.\right)$, 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. This study investigates the usage of Zn (O, S) as a buffer layer and compared it with cadmium sulphide/copper zinc tin sulphide (CZTS) structure. An integration of high doped back surface field (BSF) layer P+-CZTS is implemented to increase the performance of Zn (O, S)/CZTS. Effects of buffer, absorber, and BSF layer thicknesses and doping on open-circuit voltage, short-circuit density, fill factor, and efficiency were investigated.image (c) 2024 WILEY-VCH GmbH