Solvent-assisted Crystallization of Two-dimensional Ruddlesden-Popper Perovskite
Two dimension (2D) perovskite materials, introduced hydrophobic long-chain amine cations between the inorganic slides of three dimension (3D) perovskite, are more stable than 3D perovskite materials, which could solve the stability issue of perovskite solar cells (PSCs). However, the photovoltaic conversion efficiency (PCE) of PSCs based on 2D perovskite materials was low, due to the high dielectric and quantum confinement of 2D perovskite. In this work, we propose a solvent-assisted method to prepare 2D perovskite films, where the solvent was distributed in gradient. Therefore, the top-down crystallization process of 2D perovskite can be accurately controlled. The PCE of PSCs fabricated by solvent-assisted devices was enhanced 48%, comparing with the control device. For the packaged devices, the stability test demonstrated 94% of the initial PCE still maintained after 1500 hours storage (25℃, RH 40%). After carefully analyzing the photophysical process of carriers in PSCs based on 2D perovskite, the enhanced carrier transfer mechanism of solvent-assisted method has been proposed.