The reporter learned from the University of Science and Technology of China that Professor Xiao Zhengguo’s research group 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 used an air knife-assisted squeegee method to prepare a large-area, high-efficiency perovskite LED, which is an important step towards the commercial application of perovskite LED lighting. Related results were published in the journal Nature Communications.
Metal halide perovskite LEDs have become a new generation of LED devices because of their advantages such as wide color gamut, easy adjustment of bandgap, narrow luminous half-peak width, and ease of preparation. In 2014, it was reported for the first time that perovskite LEDs emitting light at room temperature have an external quantum efficiency (EQE) of less than 1%. In just a few years, the EQE of perovskite LEDs has exceeded 20%, which is close to commercial organic LEDs (The level of OLED) has shown 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 on 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. The EQE of the prepared perovskite LED is only 1.1%. The device area is 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 the perovskite precursor, 4-fluorobenzylamine was introduced and combined with air knife-assisted methods to make the film crystallization process more nucleation sites are formed in the medium, thereby preparing a uniform and dense perovskite polycrystalline film with a surface roughness of only 0.8 nanometers. The large-area perovskite film prepared by the knife coating method exhibits excellent uniformity in terms of thickness, surface roughness, fluorescence yield, and fluorescence lifetime. The EQE of the perovskite LED device prepared by the knife coating method is up to 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 squeegee coating, laying a foundation for the preparation of large-area flexible optoelectronic devices.
This research result fully demonstrates the feasibility of preparing large-area, high-efficiency perovskite LEDs by the squeegee method and the great prospect of applying it to commercial LED lighting.