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 $\mu $c-Si:H layers were prepared by using a different total gas flow rate ($F_{\rm total})$, behave much differently in performance, although their intrinsic layers have similar crystalline volume fraction, opto-electronic properties and a deposition rate of $\sim 1.0$~nm/s. The influence of $F_{\rm total}$ 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 $\mu $c-Si:H thin films were improved with increasing $F_{\rm total}$. 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 $F_{\rm total}$ of 300~sccm, a conversion efficiency of 8.11{\%} has been obtained for the intrinsic layer deposited at 8.5~{\AA}/s (1~\AA=0.1\,nm).