LAUSR

The external quantum efficiency (EQE) of state‐of‐the‐art planar‐structure perovskite light‐emitting diodes (PeLEDs) is mainly limited by the outcoupling efficiency, which is around 20% and decreases significantly with the perovskite thickness. Here, an approach to artificially form textured perovskite films to boost the outcoupling limit of the PeLEDs is reported. By manipulating the dwell time of antisolvents, the perovskite phase precipitation mechanism, film‐forming process, and surface texture can be finely controlled. The film surface roughness can be tuned from 15.3 to 241 nm, with haze increasing accordingly from 6% to >90% for films with an average thickness of 1.5 µm. The light outcoupling limit increases accordingly from 11.7% for the flat PeLEDs to 26.5% for the textured PeLEDs due to photon scattering at the interface. Consequently, the EQE is boosted significantly from around 10% to 20.5% with an extraordinarily thick emissive layer of 1.5 µm. This study provides a novel way of forming light‐extraction nanostructures for perovskite optoelectronic devices.