Interfacial Voids Trigger Carbon-Based, All-Inorganic CsPbIBr(2) Perovskite Solar Cells with Photovoltage Exceeding 1.33 V

A novel interface design is proposed for carbon-based, all-inorganic CsPbIBr(2) perovskite solar cells (PSCs) by introducing interfacial voids between TiO(2) electron transport layer and CsPbIBr(2) 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 CsPbIBr(2) film and thereby boost absorption ability of the resulting CsPbIBr(2) PSCs. Second, they suppress recombination of charge carriers and thus reduce dark saturation current density (J(0)) 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 CsPbIBr(2) 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. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40820-020-00425-1) contains supplementary material, which is available to authorized users.