Metal halide perovskite material is a new type of photoelectric material with a range of advantages, such as high absorption coefficient, long carrier diffusion length, high mobility, and a tunable band gap. These advantages have made metal halide perovskite the spotlight in fields of solar cells, photodetectors, light-emitting diodes, and demonstration of lasers. Moreover, the novel properties of perovskite materials provide opportunities for material innovation and new device structure design.

It is found that obtaining perovskite thin films with high crystallinity is very important for manufacturing high-performance photoelectric devices. However, it is usually very difficult to obtain all-inorganic perovskite films with good crystallinity and high grain orientation. On the one hand, all-inorganic perovskite materials are poorly soluble in polar media such as dimethylformamide or dimethyl sulfoxide. On the other hand, the crystallization of all-inorganic perovskite films is rapid and hard to control during spin coating.

To solve this problem, a research team of LIU Xingyuan from the State Key Laboratory of Optics and Applications, Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) adopted formamide (FA) doped PEDOT:PSS to induce perovskite crystallization and improve the crystallinity of perovskite films. In addition, the PEDOT:PSS film treated with FA shows better carrier transport characteristics, which improves the imbalance of carrier injection in perovskite light-emitting diodes (PeLEDs). The external quantum efficiency (EQE) of PeLEDs based on this structure reaches 9.61%, and the maximum brightness of the device reaches 185000 cd/m², which are much higher than that of low-dimensional organic-inorganic hybrid PeLEDs. This study was published in ACS Applied Materials & Interfaces.

On the basis of FA treatment, Tween 80 was used as passivator of perovskite thin films to further reduce the defect states of the perovskite films. Tween 80 helped to produce high-quality all-inorganic perovskite luminescent films with good crystal orientation, high fluorescence quantum efficiency and uniform grain size. Under the synergistic effect of FA interface treatment and Tween 80 passivation treatment, the EQE of the prepared all-inorganic PeLED is 15.02% and the maximum brightness of the device reaches 185000 cd/m2. When the initial brightness is 1000 cd/m2, the operation stability of the device is 182.5 min, which is one of the best performance among the reported all-inorganic PeLEDs devices.

Therefore, this research provided a simple and effective strategy for the preparation of all-inorganic PeLEDs with high efficiency, high brightness and ultra-long operation lifetime. Results were published in ACS Applied Materials & Interfaces under the title "Efficient in organic perovskite light-emitting diodes by inducing grain arrangement via a multifunctional interface".