Influence of the total gas flow rate on high rate growth microcrystalline silicon films and solar cells

This paper reports that high-rate-deposition of microcrystalline silicon solar cells was performed by very-high-frequency plasma-enhanced chemical vapor deposition. These solar cells, whose intrinsic μc-Si:H layers were prepared by using a different total gas flow rate (F_total), behave much differently in performance, although their intrinsic layers have similar crystalline volume fraction, opto-electronic properties and a deposition rate of ～1.0 nm/s. The influence of F_total on the micro-structural properties was analyzed by Raman and Fourier transformed infrared measurements. The results showed that the vertical uniformity and the compact degree of μc-Si:H thin films were improved with increasing F_total. The variation of the microstructure was regarded as the main reason for the difference of the J--V parameters. Combined with optical emission spectroscopy, we found that the gas temperature plays an important role in determining the microstructure of thin films. With F_total of 300 sccm, a conversion efficiency of 8.11% has been obtained for the intrinsic layer deposited at 8.5 ?/s (1 ?= 0.1 nm).