Studies on the polycrystalline silicon/SiO2 stack as front surface field for IBC solar cells by two-dimensional simulations**Project supported by the National Natural Science Foundation of China (Grant Nos. 11104319, 11274346, 51202285, 61234005, 51172268, 51602340, 61274059, and 51402347), the Solar Energy Action Plan of Chinese Academy of Sciences (Grant Nos. Y1YT064001, Y1YF034001, and Y2YF014001), the Graduate and College Student’s Innovative Project

Abstract

Interdigitated back contact (IBC) solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm. Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance.