Solution Coating of Superior Large‐Area Flexible Perovskite Thin Films with Controlled Crystal Packing

Solution coating of organohalide lead perovskites offers great potential for achieving low‐cost manufacturing of large‐area flexible optoelectronics. However, the rapid coating speed needed for industrial‐scale production poses challenges to the control of crystal packing. Herein, this study reports using solution shearing to confine crystal nucleation and growth in large‐area printed MAPbI3 thin films. Near single‐crystalline perovskite microarrays are demonstrated with a high degree of controlled macroscopic alignment and crystal orientation, which exhibit significant improvements in optical and optoelectronic properties comparing with their random counterparts, spherulitic, and nanograined films. In particular, photodetectors based on the confined films showing intense anisotropy in charge transport are fabricated, and the device exhibits significantly improved performance in all aspects by one more orders of magnitude relative to their random counterparts. It is anticipated that perovskite films with controlled crystal packing may find applications in high‐performance, large‐area printed optoelectronics, and solar cells.