Study on influence of metastable state of helium on atomic silicon concentration

Abstract

Amorphous silicon (a-Si:H) thin-films being an advantageous base for solar cells manufacturing face several disadvantages, such as relatively wide bandgap (1.7… 1.8 eV) and cells degradation effect during prolonged sun exposure (Staebler-Wronski Effect) that lowers the efficiency of the cells compared to, for instance, monocrystalline solar cells. We suggest enhancing the solar cell conversion efficiency by embedding a structure composed of single-crystal silicon nanoparticles (Si-NPs) into an a-Si:H layer. Si-NPs synthesis is performed in the glow-discharge plasma of argon-helium-silane plasma. To understand the mechanism of Si-NPs we suggest a chemical model of silane decomposition in the in the glow-discharge plasma. Numerical simulation of argon-helium-silane plasma of radio frequency (RF) discharge allowed us to obtain equilibrium concentration of radicals, defining the formation process, and to define photoelectric qualities of amorphous silicon thin-films. The influence of metastable state of helium on atomic silicon concentration has been investigated. Addition of helium in Ar+SiH4 leads plasma to increase in concentration of Si, owing to formation of the padding channel of decomposition of a silane through reactions with metastable atoms of helium.