Advanced nano-crystalline Si:H solar cell structures using novel transparent conducting light trapping oxides (TLCO)

For the achievement of maximum current density in nc-Si solar cells, transparent conducting light trapping oxides (TCLO) are developed to increase the optical path length of sunlight in the cells and to eliminate free carrier absorption in the transparent conducting oxides used at various locations in the cells. One possibility for the TCLO is a bilayer of high-mobility, titanium- or molybdenum-doped indium oxide (ITiO or IMO) and intrinsic-ZnO with specific light trapping structure. In order to increase the absorption in both short-wavelength and long-wavelength regions, we fabricate the TCLO with dual feature sizes that correspond to the whole wavelength range (up to 1150 nm). Further, fabrication and characterization of the first single-layer TCLO is presented using ITiO. Microstructural analysis of such layers reveals remarkable surface features made up of ´nanorods´ with width and length of ∼50 nm and ∼500 nm, respectively. Application of TCLOs as superstates for p-i-n nc-Si: H solar cells increased the current density by about ∼30% compared to solar cells on commercial textured substrates.