Colored a-Si:H transparent solar cells employing ultrathin transparent multi-layered electrodes

We fabricated hydrogenated amorphous silicon (a-Si: H) transparent solar cells using ultrathin transparent multi-layered electrodes (TMEs) as rear-side transparent electrodes for building-integrated photovoltaic (BIPV) windows. Each TME included a bottom layer, thin Ag layer, and optoelectronic controlling layer (OCL). The TMEs were experimentally designed to have high transparency and conductance. The fabricated a-Si:H transparent solar cells showed optimal performance with a 6.36% power-conversion efficiency and 23.5% average transmittance (500-800 nm) when TMEs with a thickness less than 160 nm were incorporated. We demonstrated that the reflection color of the cell could be tuned without serious loss of cell efficiency by varying the thickness of the OCL. The backside colors were predicted to be the coordinates on a CIE 1931 chromaticity diagram using the reflection spectrum from the cell and emission spectrum of a 50 W LED light source. The developed a-Si:H transparent solar cells exhibited high efficiency and show feasibility for incorporating various colors in the photovoltaic and aesthetic functionalities of BIPV windows.