LAUSR

Dion–Jacobson (DJ) 2D hybrid perovskite semiconductors offer improved environmental stability and higher structural diversity in comparison with their 3D analogous. However, lacking of controlled perovskite crystallization makes it a challenge to achieve high charge transport for photovoltaic devices. Here, a detailed understanding of effects on film formation during different solution‐casting processes for the DJ perovskite (PDMA)(MA)n−1PbnI3n+1 ( = 4, PDMA refers to 1,4‐phenylenedimethanammonium) in the final film structure and photovoltaic outcomes is presented. Faster removal of solvent from solution via hot‐casting or antisolvent dripping results in a more uniform thickness distribution of quantum wells. This eventually enhances carrier transport greatly along perpendicular direction and increases power conversion efficiencies. A high efficiency of 15.81% is achieved for the hot‐casting devices, which is also the highest for aromatic spacer‐based DJ perovskite solar cells. This work helps to better understand the control of film formation during solution‐casting for high performance solar cells.