Computer modeling of the front surface field layer on the performance of the rear-emitter silicon heterojunction solar cell with 25 % efficiency

Abstract

Highly conductive materials with wide band gaps are used as front surface field (FSF) layer to achieve a prominent efficiency in silicon heterojunction (SHJ) solar cells. In this study, we demonstrate an n-type hydrogenated microcrystalline silicon oxide (μc-SiO:H) layer with high conductivity and beneficial optical properties for its application in SHJ solar cells. To develop a substitute to a-Si:H (n), we started our research in the synthesis of HIT-type solar cells with three different layers, namely, a-Si:H (n), micro-crystalline silicon (μc-Si: H(n)), and μc-SiO:H (n). Owing to its better surface passivation, wide optical gap, and high conductivity, the μc-SiO:H (n) layer was employed as a substitute to a-Si:H (n). It is difficult to thoroughly investigate the effects of every parameter, such as the thickness, the electron affinity, and the doping density on the device performance experimentally. We, therefore, used a program based on the automat for simulation of heterostructures (AFORS-HET), to evaluate the limitation of the conversion efficiency, which provides a convenient way to accurately evaluate the role of various parameters. We obtained a high efficiency with open circuit voltage, (VOC) of 755.3 mV and a fill factor (FF) of 79.82 % are essential factors owing to a favorable bending of the conduction band in the μc-SiO:H (n) next to the a-Si:H (i). We achieved a high efficiency of 25.35 % using a μc-SiO:H film with both an appropriate electron affinity of 4.1 eV and the doping density of 1019 cm−3.