摘要
Elemental selenium(Se), as the world’s first but long-neglected photovoltaic material, has regained great interest recently in tandem solar cells as top cells due to its wide bandgap(~1.8 eV), simple, non-toxic and earth-abundant composition, and intrinsic environmental stability. In particular, Se possesses the lowest melting point of 217 °C among the photovoltaic absorbers reported so far, endowing Se with a unique advantage of film fabrication by blade coating the Se melt on substrate. However, the poor wettability of Se melt on widely-used photovoltaic functional layers such as TiO_(2) limits its melt processing. Here we introduce a wettability-modification strategy that decreases the contact angle of Se melt on substrate and improves the wettability by appropriately enhancing the heating temperature of molten Se while avoiding Se volatilization. We further reveal the mechanism of the inherent air stability of Se that originates from the high activation energy of oxygen chemisorption on Se(3.21 eV). This enables the realization of compact Se films through melt-based blade coating in ambient air. The resulting Se solar cells exhibit an efficiency of 3.5%. Unencapsulated devices show no efficiency loss after 1,000 h of storage under ambient conditions.
基金
supported by the National Science Foundation of China(21922512,21875264)
Chinese Postdoctoral Science Foundation(2021MD703865)
the Youth Innovation Promotion CAS(Y2021014)
。
