Design And Preparation Of Two-dimensional Hybrid Perovskite Quantum Well Crystals And Their Photoelectric Properties

Optoelectronic devices based on hybrid perovskites have been extensively studied by researchers.When they applied two-dimensional perovskites to the devices,the devices showed good stability,so two-dimensional perovskite materials became one of the hot research directions..3In order to improve the efficiency of the device,we need to understand the photoelectric physical properties of the two-dimensional perovskite itself and increase the carrier diffusion length of the material.Therefore,this paper would explore the design and preparation methods of high-crystallinity?BA?₂PbI₄crystals and study their photoelectric properties.During the research,?BA?₂PbI₄ films are used for comparison.First,in this study,a large-scale?BA?₂PbI₄ crystal was successfully grown using a slow cooling method instead of the usual natural cooling method,and a?BA?₂PbI₄two-dimensional perovskite film was grown by a one-step spin coating method.The surface morphology of each of them was observed.AFM test shows that the crystals are grown layer by layer,and the surface is smooth and continuous.In contrast,the film is densely packed with grains and the inside is rough and there are faults.In addition,The Fluorescence Microscope test further verified the results of the AFM test.At the same time,at the edges of the crystal and the edges of the crystal grains in the thin film,we found that the luminescence is different from the inside of the crystal.Subsequently,in order to verify that the crystals we grew are single crystals with high crystallinity and explain the photoelectric properties of the material itself,we performed absorption spectrum tests on the single crystal and the thin film.For crystals,we found that the absorption spectrum exhibits good band gap absorption characteristics,with sharp absorption band edges appearing at a wavelength of 525 nm.In contrast,the thin films exhibited exciton peaks due to quantum confinement effects.This shows that the internal energy bands of the crystals we grew have a higher crystalline quality.Finally,we performed Fluorescence Spectrum test and Fluorescence lifetime test on single crystal and thin film.In the single crystal test,we observed luminescence at521 nm and 560 nm,and the comparison film only had luminescence at 521 nm.From this we speculate that the luminescence at 521 nm of the crystal and the luminescence of the thin film have the same source,that is,the charge recombination caused by the rough surface.Therefore,we also grew a single crystal with bulk phase emission only at560 nm,indicating that the single crystal has a high crystallinity,a flat surface and high quality.In terms of fluorescence lifetime,we found that the fluorescence lifetime of single crystals is close to 9 times that of thin films,and in the process of double exponential fitting.The long-life ratio of the single crystal occupies the main part,and the short-life component of the thin film occupies the main part.Therefore,we can obtain that the carrier diffusion length of the single crystal is significantly longer than that of the thin film,which is more suitable as an absorption layer of the device.