Microencapsulated Perovskite Crystals via In Situ Permeation Growth from Polymer Microencapsulation‐Expansion‐Contraction Strategy: Advancing a Record Long‐Term Stability beyond 10 000 h for Perovskite Solar Cells

Organic metal halide perovskite solar cells (PSCs) bearing both high efficiency and durability are predominantly challenged by inadequate crystallinity of perovskite. Herein, a polymer microencapsulation-expansion-contraction strategy is proposed for the first time to optimize the crystallization behavior of perovskite, typically by adeptly harnessing the swelling and deswelling characteristics of poly(4-acryloylmorpholine) (poly(4-AcM)) network on PbI