Controllable Template Assisted In Situ Perovskite Growth for Display Application

Metal halide perovskites are compelling emitters for next‐generation optoelectronics, yet their translation into flexible display architectures remains limited by interfacial optical losses, non‐radiative recombination, and poor operational durability. Here we report a one‐step, template‐assisted in situ crystallization strategy that integrates CsPbX 3 (X = Cl, Br, I) directly within a porous polyethylene terephthalate (PET) membrane. A bifunctional diamine ligand molecularly bridges the perovskite and polymer, directing crystallization, promoting uniform pore filling and eliminating interfacial air gaps. This chemically defined interface suppresses non‐radiative losses, increases light outcoupling from ∼13% to 36%, and yields a film‐state photoluminescence quantum yield (PLQY) of 62%. The resulting perovskite‐integrated porous PET membrane retains ∼82% of its initial photoluminescence after 150 days under ambient conditions and exhibits a projected T 50 of ∼10 000 h, establishing benchmark stability among in situ synthesized perovskite/polymer display‐class systems. It further preserves >90% emission under repeated bending and enables inkjet‐printed full‐color RGB pixel arrays with 70% NTSC gamut. Using a highly porous PET membrane (0.5 µm pore diameter), a luminance of 1050 nits are achieved, confirming that brightness scales with pore density and is substrate limited. These results establish active encapsulation as a practical route to stable, efficient and mechanically compliant perovskite display platforms.