An insight into effect of front surface field on the performance of interdigitated back contact silicon heterojunction solar cells

Abstract

The development of interdigitated back contact silicon heterojunction has been flourishing in the field of solar cells. The front surface field has a decisive influence on the electrical field effect passivation of interdigitated back contact silicon heterojunction solar cells, and the effect of passivation layers on the performance of solar cells needs to be clarified. In this study, the two-dimension TCAD models of the doped n+-a-Si: H layer and SiNx with a fixed charge layer were established by the Sentaurus code, respectively. The space charge density and electric field intensity, carrier transportation, and distribution of current density were numerically analyzed to evaluate the effect of these two front surfaces on the performance of interdigitated back contact silicon heterojunction solar cells. The results show that for SiNx, the root cause of the field passivation is the surface fixed charge density. The combination of the doping concentration and layer thickness directly affects the field passivation of n+-a-Si: H. Based on the intuitive carrier transport vector, the selective transportation of the carrier near the surface is proved by the front surface field, which effectively inhibits the recombination. The current density distribution on the cross-section reveals that a strong front surface field is an effective way to reduce the internal recombination in particular. Considering practical operating conditions, a doping concentration of 1e20 cm−3, in combination with 7 nm layer thickness, potentially improves the front surface field of n+ a-Si: H leading to the maximum conversion efficiency of 27.41%, with the voltage increased by 32.8 mV and the fill factor reaching 86.84%.