Solvent vapor annealing-assisted mesoporous PbBr2 frameworks for high-performance inorganic CsPbBr3 perovskite solar cells

In recent years, CsPbBr 3 perovskite solar cells (PSCs) have attracted the attention of a large number of researchers due to their excellent temperature and humidity stability. And in the current studies, due to the lack of suitable solvents to dissolve PbBr 2 and CsBr at the same time, most studies have used sequential solution-processing techniques (SSPTs) to prepare CsPbBr 3 films. However, in the process of the sequential deposition of PbBr 2 and CsBr, the uneven reaction could lead to the generation of impure phase (e.g. CsPb 2 Br 5 and Cs 4 PbBr 6 ), which would deteriorate the photoelectric performance of the device. Here, a solvent-vapor annealing (SA) method has been proposed for fabricating mesoporous PbBr 2 films by exposing the PbBr 2 films in N,N -Dimethylformamide (DMF) vapor environment. The porous PbBr 2 frameworks could facilitate the reaction with CsBr to fully convert into inorganic perovskite CsPbBr 3 . A series of characterization results show that a compact, uniform and high-quality CsPbBr 3 film with large grains was obtained, where the porosity of PbBr 2 scaffold could be tuned by the volume of DMF. Consequently, the devices based on optimized PbBr 2 films treated by SA method achieved a champion power convention efficiency (PCE) of 9.60%, an open-circuit voltage ( V OC ) of 1.54 V, a short-circuit current density ( J SC ) of 7.57 mA cm −2 and a fill factor (FF) of 82.37%, compared with the devices treated by conventional thermal annealing (TA) method achieved a PCE of 8.42%, a V OC of 1.49 V, J SC of 7.31 mA cm −2 and FF of 77.30%. Furthermore, the SA treated devices exhibit more durable stability than TA treated devices, and the SA treated devices still retain 94.28% of its original PCE without any encapsulation in the ambient atmosphere after 30 days.