Locking in Color: Stable RGB Perovskite Nanocrystal Films via UV Cross‐Linking

Abstract Perovskite nanocrystals have positioned themselves at the forefront of next‐generation emitter applications due to their extraordinary optoelectronic properties, which include widely tunable narrow emission spectra and low‐cost syntheses. However, stability issues and halide ion exchange inhibit the realization of heterostructures, severely limiting their applicability and decelerating their commercialization. Here, a block copolymer templated halide perovskite nanocrystal synthesis with a post‐synthetic treatment is combined with UV‐C light to obtain ultra‐stable thin film emitters. The UV light induces cross‐linking between the polymer strands, thereby rendering them insoluble to the organic solvent and nearly impervious to halide ion diffusion while retaining the nanocrystals’ optical properties. This method enabled the fabrication of an all‐perovskite nanocrystal white light‐emitting thin film. The resulting films feature narrow linewidths ( < 95 meV) for each RGB emission peak. Additionally, the color temperature of the ’white’ light can be tuned with a color gamut approximating the Rec. 2020 standard. These RGB‐emissive phosphor films can be combined with commercial UV or blue LED backlights to create the next‐generation high‐efficiency, high‐quality phosphor‐converted white LEDs or color displays.