Hot-wire chemical vapor deposition and characterization of p-type nanocrystalline Si films for thin film photovoltaic applications

Abstract

P-type nanocrystalline Si (p-nc-Si) films were deposited by hot-wire chemical vapor deposition (HWCVD) system using SiH4, B2H6, and H2 as reactants. The effect of H2 flow rate on the material properties of p-nc-Si films were investigated using Raman spectroscopy, X-ray diffractormeter, ultraviolet–visible-near infrared spectrophotometer, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Moreover, the electrical properties, such as carrier concentration, activation energy, dark conductivity, and Hall mobility, of p-nc-Si films were also measured. It was found that H2 flow rate played an important role in forming of p-nc-Si, decreasing the deposition rate, and increasing the crystallinity of p-nc-Si films. FESEM and TEM micrographs also showed the enhancement of crystallinity with adding H2 flow rate. Furthermore, the change of microstructure at various H2 flow rates was found to affect the electrical properties of p-nc-Si films. Details of the growth mechanism in p-nc-Si films will be discussed also. Moreover, the optimum p-nc-Si film was used as window layer in n-type crystalline Si heterojunction (HJ) solar cell. After the deposition parameters were optimized, the Si HJ solar cell with the open-circuit voltage of 0.58V, short-circuit current density of 33.46mA/cm2, fill factor of 64.44%, and the conversion efficiency of 12.5% could be obtained.