Correlation between Microstructure and Photovoltaic Performance of Polycrystalline Silicon Thin Film Solar Cells

Abstract

Intrinsic polycrystalline silicon (poly-Si) thin films have been prepared by plasma enhanced chemical vapor deposition at a very high excitation frequency (100 MHz) for the development of p–i–n junction solar cells. The correlation between poly-Si microstructure and photovoltaic performance of poly-Si solar cells has been investigated as a function of deposition parameters such as deposition pressure, SiH4 flow rate and SiH4 concentration. It is found that the poly-Si microstructure including crystalline volume fraction, Xc, and crystallographic orientation is closely related to the atomic hydrogen flux during film growth, which is evidenced by plasma diagnostics in the in situ measurement of optical emission spectroscopy. Basically, with an increase in Xc, open circuit voltage tends to decrease, while poly-Si with Xc > 50% and (220) preferential orientation is essential for high short circuit current. Based on these results, the role of poly-Si microstructure in the photovoltaic performance of poly-Si solar cells is discussed.