Interfacial Voids Trigger Carbon-Based, All-Inorganic CsPbIBr2 Perovskite Solar Cells with Photovoltage Exceeding 1.33 V

Abstract

A novel interface design is proposed for carbon-based, all-inorganic CsPbIBr₂ perovskite solar cells (PSCs) by introducing interfacial voids between TiO₂ electron transport layer and CsPbIBr₂ absorber. Compared with the general interfacial engineering strategies, this design exempts any extra modification layer in final PSC. More importantly, the interfacial voids produced by thermal decomposition of 2-phenylethylammonium iodide trigger three beneficial effects. First, they promote the light scattering in CsPbIBr₂ film and thereby boost absorption ability of the resulting CsPbIBr₂ PSCs. Second, they suppress recombination of charge carriers and thus reduce dark saturation current density (J₀) of the PSCs. Third, interfacial voids enlarge built-in potential (V_bi) of the PSCs, awarding increased driving force for dissociating photo-generated charge carriers. Consequently, the PSC yields the optimized efficiency of 10.20% coupled with an open-circuit voltage (V_oc) of 1.338 V. The V_oc achieved herein represents the best value among CsPbIBr₂ PSCs reported earlier. Meanwhile, the non-encapsulated PSCs exhibit an excellent stability against light, thermal, and humidity stresses, since it remains ~ 97% or ~ 94% of its initial efficiency after being heated at 85 °C for 12 h or stored in ambient atmosphere with relative humidity of 30-40% for 60 days, respectively.