A dual promotion strategy of interface modification and ion doping for efficient and stable carbon-based planar CsPbBr3 perovskite solar cells

Abstract

Carbon-based all-inorganic cesium lead bromide (CsPbBr₃) halide perovskite solar cells (PSCs) have attracted tremendous attention owing to their low cost, simplified preparation, and outstanding stability even under harsh conditions. However, the CsPbBr₃ perovskite always suffers from an undesirable crystallization and film morphology with incomplete coverage and numerous grain boundaries. Herein, a novel dual promotion strategy combining interface modification with ion doping is proposed to achieve highly efficient and stable carbon-based planar CsPbBr₃ PSCs. A thin CsBr modified layer was first inserted between the compact TiO₂ (c-TiO₂) and PbBr₂ layers, wherein the crystallization of PbBr₂ can be enhanced and then assist the growth of perovskite grains can be provided, so that CsPbBr₃ films can reduce pinhole generation and accelerate carrier extraction, and decrease the hysteresis effect. Then an appropriate cobalt (Co²⁺) ion is doped into the CsPbBr₃ film, which not only increases the grain size with decreasing grain boundary, but also ameliorates the energy level and recombination. Consequently, the champion power conversion efficiency (PCE) of the CsPbBr₃ PSCs reaches up to 8.67% with an increment of about 30%. Moreover, the best-performing PSC without encapsulation also displays excellent humidity and thermal stability, maintaining above 98% of its initial PCE in an air atmosphere after 100 days, and over 95% under heat treatment at 85 °C after 600 hours, respectively. This study provides a promising route to boost the performance of all-inorganic perovskite solar cells.