Regulated Crystallization And Devices Structure Design Of Red Perovskite Light-Emitting Diodes

Metal halide perovskite(MHPs)has a great potential in next-generation lighting and display materials due to their excellent electrical and optical properties,such as its strong charge transfer ability,high carrier mobility,adjustable band gap.But some key problems about perovskite light-emitting diodes(PeLEDs),such as their efficiency and toxicity,are still being explored.Based on the methods of dimension regulation,architecture regulation and interface modification,we modified the perovskite/transport layer interface and precursor,regulated the crystallization behavior of perovskite,and through the additive engineering strategy,we optimized tin-based perovskite crystals to prepare high-quality perovskite films with fewer defects,so the red PeLEDs device with optimized performance can be achieved.To solve the above problems,firstly,the optical properties and the morphology of the films were regulated by adjusting the molar ratio of Cs/Pb.A two-dimensional material phenylethyl ammonium iodide(PEAI)was then added to three-dimensional perovskite CsPbI3-xBrx due to the strategies of dimensional regulation.Based on these strategies,the corresponding PeLEDs devices have achieved a maximum external quantum efficiency(EQE)of 8.26%and maximum luminance of 1725 cd m-2 peak at 664 nm.Then,the perovskite device is optimized by changing the device structure,modifying the hole transport layer(HTL)/perovskite interface with lithium fluoride(LiF),and further adjusting the thickness of LiF and electron transport layer.Finally,PeLEDs peak at 666 nm with a maximum EQE value of 19.49%and luminance up to 1966 cd m-2 were prepared.Finally,tin-based red PeLEDs devices were prepared to reduce the device toxicity.Small molecule nicotinyl hydrazine(NHD)was used as additive.Hydrazine group(-N2H3)has a strong reducing property,which reduces Sn4+to Sn2+,and the strong interaction between carbonyl group(C=O)and Sn2+can suppress the oxidation process,and this strong interaction greatly slows the crystallization rate of perovskite film,and further improves the film morphology.Finally,PeLEDs device with a maximum EQE of 0.86%and a maximum luminance of 50 cd m-2 was prepared,with emission peak at 628 nm and CIE coordinates matching the BT.2020 standard.This work provides a feasible way for realizing high performance red tin-based PeLEDs devices.