Large-area, high-efficiency fabrication of perovskite LEDs

The reporter learned from the University of Science and Technology of China that the research group of Professor Xiao Zhengguo from the School of Physics of the school has made important progress in the field of large-scale preparation of perovskite LEDs. The research team fabricated large-area, high-efficiency perovskite LEDs using an air-knife-assisted blade coating method, an important step toward the commercial application of perovskite LED lighting. The results were recently published in the journal Nature Communications.

Metal halide perovskite LEDs have become a new generation of LED devices due to their advantages of wide color gamut, easy adjustment of band gap, narrow luminescence half-peak width, and easy fabrication. In 2014, perovskite LEDs emitting light at room temperature were reported for the first time, and their external quantum efficiency (EQE) was less than 1%. In just a few years, the EQE of perovskite LEDs exceeded 20%, which is close to that of commercial organic LEDs (OLED), showing broad application prospects in the field of lighting and display. However, the current high-efficiency perovskite LEDs are all prepared based on the spin coating method, and the device area is very small, only in the order of square millimeters, which cannot meet the needs of large-area commercial lighting. The blade coating method is a method based on the solution method to prepare large-area thin films, but the crystallization process of the perovskite film prepared by the blade coating method is not easy to control, and the EQE of the prepared perovskite LED is only 1.1% at most, which the device area is also only 9 square millimeters.

In response to the above problems, Xiao Zhengguo's research group took organic-inorganic hybrid perovskite CH3NH3PbI3 as the research object. By reducing the concentration of perovskite precursor liquid, introducing 4-fluorobenzylamine, and combining with the air knife-assisted method, the film crystallization process was achieved. Thus, more nucleation sites are formed in the film, thereby preparing a uniform and dense perovskite polycrystalline film with a surface roughness of only 0.8 nanometers. The large-area perovskite films prepared by the blade coating method exhibit excellent uniformity in terms of thickness, surface roughness, fluorescence yield, and fluorescence lifetime. The EQE of the perovskite LED devices fabricated by the blade coating method is as high as 16.1% (0.04 cm2) and 12.7% (1 cm2). The perovskite LED with a large area of ??28 square centimeters emits a very uniform red light when working. At the same time, the research group also prepared flexible perovskite LEDs based on PEN/ITO substrates by the blade coating method, laying the foundation for the preparation of large-area flexible optoelectronic devices.

This research achievement fully demonstrates the feasibility of preparing large-area, high-efficiency perovskite LEDs by the blade coating method and the great prospect of applying them to commercial LED lighting.