Investigations on microcrystalline silicon films for solar cell application

Abstract

Hydrogenated microcrystalline silicon (μc-Si:H) thin film for solar cells is prepared by plasma-enhanced chemical vapor deposition and physical properties of the μc-Si:H p-layer has been investigated. With respect to stable efficiency, this film is expected to surpass the performance of conventional amorphous silicon based solar cells and very soon be a close competitor to other thin film photovoltaic materials. Silicon in various structural forms has a direct effect on the efficiency of solar cell devices with different electron mobility and photon conversion. A Raman microscope is adopted to study the degree of crystallinity of Si film by analyzing the integrated intensity peaks at 480, 510 and 520 cm-1, which corresponds to the amorphous phase (a-Si:H), microcrystalline (μc-Si:H) and large crystals (c-Si), respectively. The crystal volume fraction is calculated from the ratio of the crystalline and the amorphous phase. The results are compared with high-resolution transmission electron microscopy (HR-TEM) for the determination of crystallinity factor. Optical properties such as refractive index, extinction coefficient, and band gap are studied with reflectance spectra.