Study Of Perovskite Light-emitting Diodes Based On Interface Modification

Perovskite light-emitting diodes(Pe LEDs),with tunable light color emission,extremely narrow luminescence half-width,simple preparation process,etc.,have caused great interest among researchers.The excellent performance of Pe LEDs is inseparable from high-quality perovskite films.Perovskite belongs to ionic crystals,and the quality of its film depends on the quality of crystal growth.Since the perovskite crystals need to be grown on the substrate,the optimization of the substrate becomes more and more important.In addition,there are usually point defects such as ion vacancies or uncoordinated ions on the surface of the perovskite film.The point defects will form deep-level defect states and trap excitons,increasing the proportion of non-radiative recombination.Therefore,our work is based on the double passivation strategy,modified the lower and upper interfaces of the perovskite,and studied the changes in the properties of the film and the device before and after the modification.In the first part of the paper,the PEDOT:PSS 4083(4083 for short)solution and film properties before and after arginine doping are characterized and analyzed.We found that the p H value of 4083 solution increased from 1.6 to 5.3 with the introduction of basic arginine,making the solution change from strong acid to weak acid,effectively reducing the corrosion of ITO during the spin coating process.At the same time,due to the existence of the lone pair of electrons on the N atom in the arginine molecule,it can undergo a Lewis acid-base reaction with the PSS in 4083,which makes the polystyrene sulfonic acid(PSSH)deprotonated into PSS^- and interacts with arginine,ultimately reduces the content of free PSSH.In addition,we found that the film-forming properties and optical properties of the 4083 film did not change significantly before and after modification.In the second part of the thesis,the effects of different substrates on the properties of perovskite films and the performance of light-emitting devices are studied.First,the quality and crystallization of the perovskite film were explored,and it was found that the 4083-doped arginine substrate was wetted by the perovskite precursor solution at the highest degree and the obtained perovskite film had the best crystallinity.Next,we analyze the fluorescence characteristics of the perovskite film,and found that the photoluminescence(PL)intensity of the perovskite grown on the 4083-doped arginine substrate is the highest.The reason for the increase in PL may be:(i)the increase in low-dimensional perovskite phase components leads to enhanced dielectric confinement,inhibits exciton dissociation,and promotes exciton recombination luminescence;(ii)perovskite crystallinity is improved,the film defects are reduced,and the proportion of radiation recombination is increased;(iii)indium ion defect recombination centers are reduced,which reduces the probability of exciton quenching.Subsequently,we found that PSS interacts with the amine salt in the perovskite component,which adversely affects the crystallization and low-dimensional phase formation of the perovskite,and the modification of the substrate by arginine can weaken this effect.Finally,the maximum luminance of the Pe LEDs based on the 4083-doped arginine substrate is 14375 cd m^-2 and the maximum external quantum efficiency is 4.7%.In the last part of the paper,based on the second part of the research,a perovskite light-emitting diode with good performance was obtained by surface modification of the perovskite film.The current efficiency of the device is 31.8 cd A^-1,and the EQE is 7.7%which is 1.75times higher than LED made without surface modification.Surface modification has no effect on the morphology and crystallization of perovskite,and the improvement of device performance is mainly due to the improvement of photoluminescence intensity of perovskite film which is benefit by the increase of exciton binding energy and the decrease of Pb²⁺ and Pb defects.