Performance Optimization of ZnS/CIGS Solar Cell with over 25% Efficiency Enabled by Using a CuIn3Se5 OVC Layer

Chalcopyrite CIGS solar cells have been demonstrated with the highest efficiency for thin-film solar cell families. Herein, the effects of thickness and bandgap of cadmium (Cd) free ZnS buffer layer grown on CIGS absorber with an ordered vacancy compound (OVC) at buffer/absorber interface in CIGS solar cell structure have been investigated using ADEPT 2.1 simulator. The ZnS buffer possesses a wider energy bandgap than the traditional CdS buffer layer, which substantiates the higher conversion efficiency of this solar cell, allowing the photons of lower wavelength into the CIGS layer. Besides, CuIn 3 Se 5 has been used as an OVC layer that assists to improve the conversion efficiency to an optimized level of over 25% by reducing the recombination rate. Moreover, the optimized short circuit current (J sc ) and corresponding open-circuit voltage (V oc ) yield a higher fill factor (FF) of 86.22%, which, therefore, results in an optimum efficiency of the CIGS cell estimated as 25.68% under AM 1.5 irradiance.