Phosphonic Chloride Assisted Fabrication of Highly Emissive Mixed Halide Perovskite Films in Ambient Air for Blue Light-Emitting Diodes.

Blue perovskite light-emitting diodes (LEDs) have emerged as promising candidates for full-color display and lighting applications. However, the fabrication of blue-emitting perovskite films typically requires an inert environment, leading to increased complexity and cost in the manufacturing process, which is undesirable for applications of perovskite LEDs. Herein, we report a strategy to fabricate bright blue-emitting perovskite films in ambient air by incorporating phosphonic chlorides in a perovskite precursor solution. We used two different phosphonic chlorides, diphenylphosphonic chloride (DPPC) and phenylphosphonic dichloride (PPDC), and comparatively studied their effects on the properties of perovskite films and the blue LEDs. It is found that PPDC possesses a stronger chlorination ability due to higher hydrolysis reactivity; meanwhile, it has a stronger interaction with the perovskite compared to DPPC, resulting in an improved film quality and enhanced blue emission with a photoluminescence quantum yield of 45%, which represents the record value for the air-processed blue perovskite films. Blue perovskite LEDs are fabricated, and the emission wavelengths are effectively tuned by controlling the concentration of phosphonic chlorides. Benefiting from the optimized perovskite films with reduced nonradiative recombination and promoted charge injection and transport, the PPDC-derived blue perovskite LEDs exhibit improved performance with an external quantum efficiency of 3.3% and 1.2% for the 490 and 480 nm emission wavelength, respectively.