Low-cost and high-performance selenium indoor photovoltaics

Abstract

Selenium (Se), as the world's oldest photovoltaic material, has reemerged as a promising absorber material for indoor photovoltaics (IPVs) due to its suitable wide bandgap of ∼1.9 eV, nontoxicity, and excellent inherent stability. However, despite the low material cost of Se, conventional high-performance Se photovoltaic devices usually employ high-cost Au as the electrode, significantly increasing the cost of Se-based devices and restricting their future commercialization. Here we replace high-cost Au with low-cost Cu as the electrode, reducing the cost of Se devices by about one order of magnitude. We further introduce an isolation layer of MoO_x between Se and Cu films; this prevents the reaction between Se and Cu to form CuSe during the thermal evaporation of Cu, which significantly lowers the device performance. The resulting Se cells achieve an efficiency of 10.4% under indoor illumination at 500 lux, comparable to that of Au electrode-based Se devices and superior to that of the current IPV industry standard of commercialized amorphous silicon cells with indoor photovoltaic efficiency below 10%. Unencapsulated devices also exhibit negligible efficiency loss after 1000 h of storage under ambient conditions.