Component Engineering Enables Perovskite Melt Processing And High-Performance X-Ray Detection

Organic-inorganic hybrid perovskites have shown great application potential in solar cells,light-emitting diodes,and photodetectors due to their large light absorption coefficient,long carrier diffusion length,high tolerance,and excellent optoelectronic properties.However,its low stability limits its application in optoelectronic devices.This is due to the ionic nature and soft structure of the perovskite material,which makes it very sensitive to the surrounding environment and actual operating conditions,such as electric field,light,oxygen,heat,and humidity,which may cause defects or even lattice distortion in the perovskite crystal structure.This paper aims to improve the stability and performance of MAPb Br₃ perovskite single crystal and two-dimensional lead-based iodide perovskite through component engineering and provide new ideas for their applications in optoelectronics.The main innovations and conclusions of this paper are as follows:In this article,the structure and composition of MAPb Br₃ perovskite single crystals and two-dimensional lead-based iodide perovskites were regulated by component engineering to improve their stability and performance in the target environment.The authors prepared MAPb Br₃ single crystals and Na-doped Na-MAPb Br₃ single crystals by combining inverse temperature crystallization with evaporative solvent methods.They studied the effect of Na doping on the growth of MAPb Br₃ single crystals,optical bandgap,and lattice structure.The results showed that Na ions can reduce homogeneous nucleation sites during crystal growth,making it easier to obtain large single crystals while improving the transmittance of the crystals.Na ion doping can slightly change the optical bandgap of MAPb Br₃ single crystals and increase their lattice constant.Na-MAPb Br₃ single crystals have lower dark current density and higher photocurrent/dark current ratio than MAPb Br₃ single crystals.Theμτof Na-MAPb Br₃ single crystals is 1.22×10^-2 cm² V^-1,μis 162.418 cm² V^-1 s^-1,both larger than those of MAPb Br₃ single crystals,indicating that Na-MAPb Br₃ single crystals have fewer defects.The stability of Na-MAPb Br₃ single crystals is also better than that of MAPb Br₃ single crystals,indicating that Na ions entering the interstitial sites of MAPb Br₃ lattice inhibit the migration of Br ions.We also provided a simple and fast method for synthesizing（2-Et）₂PbI₄perovskites,which shortens the synthesis time of（2-Et）₂PbI₄ perovskite from 7 days to1 day.By replacing the A-site organic long-chain cation of two-dimensional lead-based iodide perovskites with a branched chain near the amino group on the long-chain cation,it is possible to change the melting point of perovskites.When there are branched chains on long-chain cations near amino groups,it can significantly reduce the melting point of perovskites.We analyzed six kinds of perovskite powders prepared by this method and their melt films and summarized three requirements for melt processing of perovskites.Finally,we used a simple hot-pressing method to prepare（2-Et）₂PbI₄perovskite devices and tested their electrical properties.The results showed that（2-Et）₂PbI₄ perovskite has a broad application prospect as an intermediate layer between device electrodes and active layers.