Influence of the molybdenum thickness on the conversion efficiency of thin-film a-Si:H solar cells grown on a 304 stainless steel substrate

Abstract

This paper reports the conversion efficiency of thin-film a-Si:H solar cells grown on a 304 stainless steel (SS) substrate with varying molybdenum (Mo) buffer layer thickness. A conversion efficiency of 4.12% was achieved for thin-film a-Si:H solar cells grown on a 2-μm-thick Mo film/304BA SS substrate. The current density–voltage (J–V) curve shows that the shunt resistance (Rsh)/series resistance (Rs) were 82.5/58.1Ω and 290.6/16.7Ω for cells grown on the raw 304BA SS substrate and the 2-μm-thick Mo film/304BA SS substrate, respectively. The results from the secondary ion mass spectroscopy (SIMS) indicated that a Mo film thickness exceeding 2-μm could effectively prevent iron (Fe) impurity diffusion from the SS substrate into the thin-film a-Si:H solar cells. Fe impurities in a Si thin film forms deep-level defects that degenerates the junction interface in each layer of the cell structure thereby decreasing the Rsh and increasing the Rs of the solar cell. A high open voltage (Voc) and short current density (Jsc) can be achieved by adding a Mo buffer layer thereby improving the conversion efficiency of the solar cell.