Strong Polarized Photoluminescence from Stretched Perovskite‐Nanocrystal‐Embedded Polymer Composite Films

Polarized light is very necessary to achieve functional optical systems for display, imaging, and information storage. Luminescent materials with polarized emission are of great interest to achieve polarized light. Here, strong polarized photoluminescence from stretched perovskite‐nanocrystal‐embedded polymer composite films is reported by combining an in situ fabrication process with controllable mechanical stretching. The material characterizations show that perovskite quantum dots (QDs) in stretched composite films are oriented aligned into wires along the stretching direction. The optical measurements illustrate that the stretched composite films exhibit not only isotropic absorption but also polarized photoluminescence emission. This feature can be explained with their unique structure of “QD‐aligned wires”. The achieved polarization ratio is consistent with the calculated results by considering the dielectric confinement of optical electric field and exciton–exciton interactions. In addition, the optimized stretched composite films show strong photoluminescence emission with a polarization ratio of up to 0.33 and a quantum yield of 80%. The use of these composite films in liquid crystal display backlights has potential to increase the light transmittance of polarizers from 50% (without considering the optical loss) to 65%, which is of great significance to improve the energy efficiency. Perovskite nanocrystal‐embedded polymer composite films, which exhibit not only isotropic absorption but also strong polarized photoluminescence (PL) are fabricated by combining an in situ method and controllable mechanical stretching. The stretched composite films contain “quantum‐dot‐aligned wires” along the stretching direction in the polymeric matrix. The polarized PL can be explained by the dielectric confinement effect and exciton–exciton interactions.