Numerical Modelling of Tandem Solar Cells

In this work, Solar Cell Capacitance Simulator (SCAPS-1D), a software primarily developed to analyze single-junction devices, was used to effectively model photovoltaic thin-film multi-junction solar cells. The tandem configuration in this study consists of a modified cadmium telluride based top cell which uses n-MZO (magnesium doped zinc oxide) as an emitter layer (as opposed to n type cadmium sulfide) and a silicon-based bottom cell with n type silicon as an emitter layer. Parameters including the thickness of the emitter and absorber layers were varied to improve the open circuit voltage to 1.4 V, short circuit current to 24.5 mA/cm2, fill-factor to 85.9%, and overall efficiency of the device to 28.8%. This numerical work supports the study of tandem-devices and their potential to optimize efficiency by making use of the entire spectrum of solar irradiation.