Water assisted chlorination enables ambient air fabrication of mixed halide perovskite films for blue light emitting diodes

Blue perovskite light emitting diodes (LEDs) have attracted remarkable attention in recent years owing to their potential in full-color display and lighting applications. However, blue-emitting perovskite films usually require to be fabricated in inert condition, which increases the fabrication complexity and cost of perovskite LEDs, being unfavorable for practical applications. Herein, we report a strategy to fabricate blue perovskite films in ambient air with high humidity for LED applications. Diphenylphosphinic chloride (DPPOCl) is introduced into perovskite film, which can react with the water in air and release chlorine ion, thus leading to the chlorination of perovskite and the consequent blueshifted luminescence. Meanwhile, the PO groups can passivate the perovskite film and suppress nonradiative recombination. Based on the ambient air fabricated blue-emitting perovskite films, perovskite LEDs are constructed, which exhibit bright and spectrally stable electroluminescence (EL). The emission wavelength of the LEDs can be effectively tuned from cyan to pure blue by varying the concentration of DPPOCl. Our work demonstrates a feasible approach to fabricate blue perovskite films in high humidity air, which could contribute to lowering down the fabrication cost of blue perovskite LEDs and further boosting their applications in display and lighting.