The Design of Boron Epitaxial Emitter for IBC Solar Cells.

Abstract

The efficiency of P-type Cz-Si base solar cells shows a severe degradation of up to 10% relative under illumination (light-induced degradation) or minority carrier injection in the dark, due to the existence of well-known boron-oxygen defect. N-type Silicon substrate as an alternative material has a large potential to be widely developed in industry because of its tolerance to impurities and no boron-oxygen related light-induced degradation even in the presence of a significant amount of oxygen. In this project n-type substrate silicon solar cells were fabricated and investigated. In previous studying at IMEC, the performance of n-type solar cell, of which emitter was formed by APCVD can obtain an efficiency up to 17.0%. The impact of silicon wafer starting surface before CVD is considered as one of main factor that influences the efficiency. We expect to find out the reasonable thickness of raw substrate to be removed by saw damage removal and chemical polishing. The emitter is going to be applied to interdigitated back contact (IBC). The second purpose is to study the influence of thermal oxidation on emitter doping concentration profile. In the fabrication of bulk crystalline silicon solar cells always involves 2~3 high temperature processes. Thus how much the thermal oxidation will affect the cells is the other goal of this study. In addition, two types of passivation will be investigated. Finally, an IBC solar cells simulation were performed with three types of emitter doping profile, gaussian function, complementary error function and box emitter doping profile.