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Triple‐mesoscopic perovskite solar cells (PSCs) have attracted intensive attention due to the high stability, simple fabrication process, and low material cost. In this structure, the perovskite layer is hosted by a triple‐mesoscopic scaffold of TiO2/ZrO2/carbon, and thus the crystal quality is sensitive to the thermal annealing process. Typically, the annealing process is conducted in a petri dish, for which the solvent evaporation of the perovskite precursor is slowed down, but not controllable and designable. To control the solvent evaporation, annealing chambers are first designed with different shape and vapor releasing channels. Then, physical simulations are performed by a finite element method, and it is found out that the chamber with a crowned top and releasing channels on the bottom sides can realize homogeneous distribution of the solvent vapor. To verify the simulation results, chambers are fabricated by 3D printing technique, for which the printing deviation can be as low as 100 µm. By balancing the solvent evaporation and release, the optimal solvent evaporation is achieved of the perovskite precursor in the triple‐mesoscopic scaffold. This work offers a method to obtain homogeneous distribution of solvent vapor, and provides a new insight into understanding the influence of solvent evaporation during the thermal annealing process for PSCs. [ABSTRACT FROM AUTHOR]

The anion exchange between MAPbX3 (X = I− or Br−) and MAX salts in a solution environment is investigated. We find that I− can enter MAPbBr3 single crystals (SC) in millimeter scale, while Br− can only penetrate the surface of MAPbI3 SC in a micrometer scale. Due to the lattice variation, the reaction is partially reversible. [ABSTRACT FROM AUTHOR]

Metal hybrid halide perovskite solar cells (PSCs) are very sensitive to air, and it is challenging to obtain air-processed, air-stable, and highly crystalline perovskite films. Photovoltaic performance decays dramatically due to air humidity influence with power conversion efficiency (PCE) of most air-processed PSCs < 15%. In this work, we develop a facile method to air-processed, highly crystalline (MA0.2FA0.8PbI3)1.0(CsPbBr3)0.05 perovskite films in ambient air with large grain size and low trap density based on mix-cation single crystal engineering. This method shows 75% increase in grain size and 28% decrease in trap density than conventional molecule/ion solution mixing-processed method. The large grain, low trap density, andhigh crystalline perovskite films result in high-efficient and air-stable PSCs. Consequently, the PCE increases to 36.7% from 12.56% for conventional molecule/ion solution mixing-processed devices and to 17.17% for single crystal engineering-based ones. Furthermore, benefiting from high moisture resistance of mix-cation single crystal engineering-based films, the PSC air stability has been improved significantly and 72% of the initial performance retains after 40 days of storage in ambient environment with a relative humidity of 60% at 25 °C without any encapsulation, with a 26% slower degradation rate than conventional solution-mixing method. [ABSTRACT FROM AUTHOR]