Degradation study of carrier selective contact silicon solar cells with ageing: Role of silicon surface morphology

Abstract

Ageing effect on the performance of Ag/ITO/MoOx/n-Si/LiFx/Al carrier selective contact (CSC) silicon solar cells has been investigated based on silicon surface morphology (planar, different pyramid sizes, and chemical polishing of pyramids). The cells with small silicon pyramids (~2 µm) have shown better stability with time than the medium/large pyramids (~5/~8 µm). The chemical polishing of pyramid peaks and valleys has further reduced the cells ageing effect due to minimization of the microstructural stress (tensile in the valleys and compressive at the peaks) at the MoOx/n-Si interface, which has been verified indirectly with cells fabricated on a planar surface. The cell’s performance degradation based on morphology points out the instability of the MoOx layer and Schottky barrier reduction, which results in hole-transport hindrance at the MoOx/n-Si junction with the S-shape in J-V graphs under illumination. The ageing effect on device performance is further investigated using the Sentaurus TCAD simulations with the MoOx layer work function variation, and the study indicates the band bending reduction (minimal carrier inversion) and hole transport barrier at the junction region.