High-performance carbon-based all-inorganic CsPbI₂Br perovskite solar cells via ethylammonium iodide and phenethylammonium iodide synergistic passivation

Hole transporting layer (HTL)-free, carbon-based all-inorganic CsPbI₂Br perovskite solar cells have attracted great attention with suitable band gap, excellent thermal stability, low manufacturing cost and simplified procedure processes. Focusing on issues including energy level match and contact between the carbon electrode and the perovskite layer that limit the device performance, passivation strategies are widely applied on the interfaces within perovskite solar cells. Herein, the effect of synergistic passivation of ethylammonium iodide (EAI) and phenethylammonium iodide (PEAI) on all-inorganic perovskite (CsPbI₂Br) solar cells is studied for the first time. Results indicate that α-/δ-phase heterojunction and localized 2D/3D heterojunction formed on the CsPbI₂Br film surface tend to reduce the trap density and promotes the energy level gradient arrangement. In addition, EA⁺ ions enter into the lattice and passivate the bulk phase defects of perovskite. As a result, the synergistic passivated devices (active area 0.0706 cm²) exhibit an increased PCE from 11.74% to 13.76% and a high fill factor (FF) of 80.32%, as well as promising long-term stability.