Insights into the role of the interface defects density and the bandgap of the back surface field for efficient p-type silicon heterojunction solar cells

Abstract

An n-type silicon wafer appears to be an excellent base material for high efficiency silicon heterojunction solar cells with high annual energy output. The further development of viable p-wafer cells would open many industrial photovoltaic options. Here, the role of the interface defects density and the bandgap of the back surface field of p-type silicon heterojunction solar cells have been investigated in detail to provide guidelines for achieving high performance. The result indicates that the output characteristics of the heterojunction solar cells are sensitive to the density of interface defects (D_it) at both sides of the c-Si surface. However, the output parameters primarily affected by D_it at the front and rear side are not identical. Back surface field (BSF), which aims to reduce photo-generated carriers' recombination at the rear interface, has also been optimized by adjusting the bandgap to improve the collection efficiency. Finally, based on experimental results, we propose that the conversion efficiency of p-type silicon heterojunction solar cells could be increased beyond 23% by efficiently regulating the bifacial D_it and the bandgap of the BSF layer.