Research On Performance Optimization Of Perovskite Light Emitting Devices

Organic-inorganic halide perovskite materials have been intensively investigated due to advantages of excellent luminescence characteristics,high defect tolerance,rich materials,low cost,and solution processability.Perovskite light-emitting diodes based on above organic-inorganic halide perovskite materials are expected to become the next generation of display technology owing to high purity and tunable color.However,the efficiency of perovskite light-emitting diodes is still very low.In this thesis,the performances of perovskite light-emitting diodes are improved from two aspects of the hole transport layer and perovskite films.?1?We found that there is a large injection barrier between the common hole transport layer and the perovskite layer due to the deep energy level of perovskite materials.Based on this,we modified the energy level of PEDOT:PSS by adding appropriate amount of PSS into PEDOT:PSS and successfully increased the highest occupied molecular orbital?HOMO?level of PEDOT:PSS from-5.08 to-5.29 e V.The maximum brightness and current efficiency of the optimal perovskite light-emitting diode reached 1534 cd m^-2and 0.69 cd A^-1,with improvement factors of 42%and38%,respectively,due to reduced hole injection barrier between PEDOT:PSS and perovskite layer and enhanced excitons recombination in the perovskite layer.?2?In this part,we optimized the process of perovskite films so as to enhance its film quality.The best process conditions of perovskite films were 7000 rpm for 60 s,followed by 80°C annealing for 10 min on a hot plate in perovskite light-emitting diodes with one-step spin coating.Then,we introduced multi-step spin-coating technique to further improve the quality of the perovskite films on the basis of one-step spin coating.The multi-step spin-coating technique can effectively improve the coverage of perovskite films,reduce the size of perovskite crystal,and form a thin and dense perovskite layer.The resulting maximum brightness and current efficiency of the perovskite light emitting diode are 7872 cd m^-2and 2.13 cd A^-1.?3?Polymer additives are added into the perovskite precursor solution to further improve the perovskite film.Firstly,we used PLA as additive,the experimental results were unsatisfactory because of PLA failed to improve the coverage of the perovskite films.Then,the viscous polymer PEO was used as an additive to prepare smooth and dense perovskite films.We successfully improved the performances of perovskite light-emitting diodes and obtained a maximum brightness and a maximum current efficiency of 6762 cd m^-2and 7.6 cd A^-1,respectively.In summary,we have successfully improved the performances of perovskite light-emitting diodes using a modified hole transport layer and an optimized perovskite film.The above-described hole transport layer modification approach and multi-step spin-coating technique can also be applied to other optoelectronic devices including organic light emitting diodes and perovskite solar cels to improve device performances.