Optical and Electrical Effects of p-typeμc-SiOx:H in Thin-Film Silicon Solar Cells on Various Front Textures

Abstract

p-type hydrogenated microcrystalline silicon oxide (µc-SiOx:H) was developed and implemented as a contact layer in hydrogenated amorphous silicon (a-Si:H) single junction solar cells. Higher transparency, sufficient electrical conductivity, low ohmic contact to sputtered ZnO:Al, and tunable refractive index make p-type µc-SiOx:H a promising alternative to the commonly used p-type hydrogenated microcrystalline silicon (µc-Si:H) contact layers. In this work, p-type µc-SiOx:H layers were fabricated with a conductivity of up to 10−2 S/cm and a Raman crystallinity of above 60%. Furthermore, we present p-type µc-SiOx:H films with a broad range of optical properties (2.1 eV < band gapE04<2.8 eV and 1.6 < refractive indexn<2.6). These properties can be tuned by adapting deposition parameters, for example, the CO2/SiH4deposition gas ratio. A conversion efficiency improvement of a-Si:H solar cells is achieved by applying p-type µc-SiOx:H contact layer compared to the standard p-type µc-Si:H contact layer. As another aspect, the influence of the front side texture on a-Si:H p-i-n solar cells with different p-type contact layers, µc-Si:H and µc-SiOx:H, is investigated. Furthermore, we discuss the correlation between the decrease ofVocand the cell surface area derived from AFM measurements.