Simulation-based optimization of CdS/CdTe solar cells incorporating MXene-enhanced SnO2 buffer layer: insights from experimentally validated material properties

Abstract

Cadmium telluride (CdTe) is considered as an outstanding material for thin film solar cell with a direct bandgap of 1.5 eV and high optical absorption. However, a short lifetime of minority carriers in absorber layer and lower photogenerated carrier concentration hinders the improvements in open circuit voltage (V_OC) and fill factor (FF) of the device. Various techniques such as passivation, doping, charge reflective coating and buffer layers are employed to overcome defects in CdTe layer and improve charge extraction for efficient device. A buffer layer in CdTe based PV device is used to enhance the device performance and stability. The SnO₂ is widely used in optoelectronics applications including solar cell due to its remarkable optoelectronic properties. Here, the photovoltaic (PV) performance of SnO₂ buffer layer in CdTe based solar cell has been investigated by numerical analysis using SCAPS-1D simulation software. The PV device comprises of SnO₂ buffer layer, CdS window layer, CdTe absorber layer and metal back contact. The optimum thickness of buffer layer, window layer and absorber layer were varied including the variation in donor density of SnO₂, Cds and acceptor density of CdTe. Furthermore, the temperature effect was considered along with the tuning of series and shunt resistance to investigate their effect on device performance. The SnO₂ buffer layer properties were improved with addition of 2D MXene materials. The Ti₂C₃ MXene is used to tune the bandgap, work function and importantly electron affinity of SnO₂ buffer layer using different MXene mixing concentration. The optimized simulated device using SnO₂ buffer layer modulated with 0 and 0.1 wt% MXene concentration demonstrates enhancement in FF from 82.87 % to 84.82 % mainly due to work function tuning and improved band alignment, thus increasing PCE from 21.86 % to 22.42 % respectively. In addition, the PV device showed an external quantum efficiency of around 90 % at visible wavelength. These results indicate the effectiveness of numerical modelling using SCAPS-1D for the MXene incorporation in PV.