Interface Modification For Efficient Metal Halide Perovskite Light-Emitting Diodes

Metal halide perovskites(MHPs)have outstanding electrical and optical properties,such as high defect tolerance,good charge transport ability,tunable bandgap,high photoluminescence quantum yield,and solution processability.They have become a popular class of materials and been widely applied to optoelectronic devices.Among them,perovskite light-emitting diodes(PeLEDs)are one of the most significant applications for MHPs.Through adjusting the composition of the perovskite precursor solution,the emission spectrum of the perovskite films can be easily tuned from red to blue wavelength,and the color purity of perovskite films is higher than that of organic light-emitting diodes.However,the quality of perovskite films prepared by the solution method is limited by the crystallization of the crystal.The crystallinity and orientation of the crystal have a large impact on the performances of PeLEDs.In addition,the surface and bulk of perovskite films have many defects,which not only cause severe non-radiative recombination losses and limit the device efficiency of PeLEDs,but also accelerate the degradation of PeLEDs and reduce device operational lifetime.Nowadays,the luminescence performances of PeLEDs is not good enough,and there is still a long way to go before their industrial applications.We are committed to studying the influence of interface modification strategies on the luminescence performances of PeLEDs,and revealing the optimization effects of different interface engineering strategies on perovskite films.Firstly,we adjusted the interface of the perovskite films themselves.The passivation effect of phenylmethanamine(PMA+),phenylethanamine(PEA+),and phenylbutylammonium(PBA+)organic spacer cations on perovskite films are revealed based on theoretical calculations and various characterization techniques.The PEA+ organic spacer cation with suitable length of alkyl chain have the best defect passivation effect,and could effectively promote the external quantum efficiency(EQE)of PeLEDs.Secondly,we utilized in-situ grazing incidence X-ray diffraction characterization technology to explore the crystal growth control of the alcoholamine molecule(ethanolamine)modified PEDOT:PSS hole transport layer(HTL)on the above perovskite films,which unraveled the critical role of crystallization dynamics on luminescence characteristics of PeLEDs.Finally,we adopted PEA+ organic spacer cations to construct high-quality blueemitting perovskite films for effective dimensional control and defect passivation.Also,we selected organic molecule propanolamine(PAA)for interface modification of PEDOT:PSS/perovskite,which further improved the crystallization and interface conditions of perovskite films.As a result,the small-area blue PeLEDs(measuring at 10 mm2)emitting at 480 nm with an EQE of 6.6%were successfully achieved,and the large-area blue PeLEDs with 100 mm2 based on the same fabrication process also achieved a decent EQE up to 5.1%.Our above works provide a feasible solution with reference significance for the preparation of efficient PeLEDs.