A research group, led by Prof. XIAO Zhengguo from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences, has developed large-area and efficient sky-blue perovskite light-emitting diodes (PeLEDs) by blade-coating supersaturated perovskite solution.
Metal halide PeLEDs can achieve high luminance at low voltage due to their high electrical conductivity, making them ideal for the next generation of energy-saving lighting. Blue/sky-blue PeLEDs are essential for white lighting, but the EQE of blue light is relatively low since the crystallization process of such perovskite films is difficult to control, which results in poor film quality.
The researchers in this work adjusted the composition of perovskite into CsPb(Br0.84Cl0.16)3 based on their previous robust perovskite blade-coating technique for red PeLEDs. They added additional halide amine additives to limit the growth of perovskite grains and passivate the traps, to achieve the sky-blue emission.
Meanwhile, they partially replaced dimethyl sulfoxide (DMSO) with dimethylformamide (DMF) to obtain a more volatile and supersaturated perovskite precursor solution. Perovskite crystal nucleus will precipitate directly from inside of the supersaturated solution in the process of blade-coating, which can effectively increase the density of the nucleus and accelerate the process of nucleation, crystallization, and film-forming, to prepare uniform perovskite films with small grains.
The EQE for the blue/sky-blue PeLEDs prepared by the blade-coating method reached 10.3%, and the luminescence uniformity and brightness in an area of 28cm2.
This work could represent an important step to the commercial application of PeLED lighting.