Commercial large area bi-layered zinc oxide as front contact in tandem silicon thin film solar cell

Commercial large area bi-layered ZnO front contact (FTCO) in tandem Si (amorphous/microcrystalline) solar cells was investigated. Different haze value and doping level of the FTCO were analyzed. From the SEM and EQE investigations, it was verified that the surface morphology of the ZnO significantly influence the μ-Si quality. Although the light trapping effect was suppressed in the low haze cell, the improved carrier-collection ability still maintained the cell efficiency. The initial cell efficiency was slightly improved from 10.27% to 10.46% by using the low haze FTCO. In addition, the carrier-collection ability could be further enhanced by using a bilayer ZnO with lower surface roughness and doping level. In this paper, the test cells with such low haze and low surface doped FTCO exhibited highest efficiency 11.17%. The bilayer FTCO was then successfully implemented in the mass production of large area (1.1*1.3m) modules, and more than 1 W power improvement was acquired.