Fabrication of Highly Efficient CdSeTe/CdTe Thin Film Solar Cells with Emitter-Less Cell Structure

With excellent optical and electronic properties, tin oxide (SnO2) is a promising electron transport layer (ETL) in CdTe thin film solar cell. However, CdTe solar cells with undoped SnO2 ETLs demonstrate poor efficiencies with relatively low open-circuit voltage (VOC). In this report, Mg-doped SnO2 (MTO) thin films were fabricated by magnetron co-sputtering technique and employed as the ETLs/window layers in CdTe-based thin film solar cells. The VOC has been significantly improved by doping Mg into the SnO2 layers, regardless of whether the contacting absorber layer is CdSeTe or CdTe. Upon Mg doping the trap density was reduced from 4.02 to 1.62 × 1013 cm−3, indicating that significant part of the recombination defects at the interface were effectively passivated upon Mg doping in the SnO2 films, which is responsible for the significant improvement in VOC.