breakthrough in white light perovskite LED
Recently, Prof. Xuanli Ye and his team from the State Key Laboratory of Luminescent Materials and Devices of South China University of Technology have published a research paper titled "Utilization of Traded Optical Modes for White Perovskite Light-Emitting Diodes with Efficiency over 12%" in the international top journal Joule.
White light emitting diodes (LEDs) are an important part of lighting and display applications, which consume a large amount of electric energy. Therefore, it is of great significance to realize efficient white light LEDs for energy saving and emission reduction. After recent years of development, metal halide perovskite LED has shown great potential and is expected to become the next generation of luminescence technology.
Among them, the external quantum efficiency of red and green perovskite LEDs increased rapidly from less than 1% to more than 20%, while the efficiency of blue perovskite LEDs also exceeded 12%, but the development of perovskite white light devices is still very slow.
In addition, based on optical simulation analysis, in the traditional perovskite LED devices, more than 80% of the photons are confined in the device and cannot be emitted, making the light extraction efficiency of perovskite LED generally less than 20%, which has become another key problem restricting its further development.
According to the scientific problem, the team put forward a simple and effective method, to solve the light extraction efficiency of perovskite LED limited, and the poor performance of white light device, namely by reasonable design of multi-layer semi-transparent electrode (LiF/Al/Ag/LiF), titanium to blue light calcium deposits with red perovskite nanocrystalline layer near field coupling, realize the light extraction efficiency greatly increased, so as to build a high performance of white light perovskite LED device.
Generally, due to the great difference between the refractive index of the perovskite luminescent layer and that of the organic interface layer, total reflection will be caused at a specific Angle, which induces the waveguide mode in the perovskite LED device, making part of the photons emitted by the luminescent layer oscillate repeatedly inside the device and cannot escape outside the device. The evanescent wave generated in the total reflection process will continue to induce the generation of surface plasma polariton (SPP) mode.
In addition, the substrate pattern and the presence of parasitic absorption reduce the probability of photons propagating to the outside of the device (the air end). Fortunately, produced by total reflection and SPP evanescent field of energy can be within the scope of the near field through to the next layer medium, it provides an opportunity to take advantage of them, and to suppress the perovskite LED optical waveguide mode and SPP mode, can through the photon tunneling effect, the evanescent wave absorption and SPP absorption of three kinds of near field coupling effect.