Green,Blue And White Light-emitting Diodes With Quasi-two-dimensional Perovskites

Perovskite light-emitting diodes have good application potential in both display and lighting because of their tunable light emission wavelengths,high color purity,low temperature solution processing and so on.Quasi-2D perovskites can be achieved by introducing long-chain ammonium ions into traditional three-dimensional perovskite materials.And with the use of quasi-2D perovskite we can get more efficient perovskite light-emitting diodes.However,the research on quasi-two-dimensional perovskite light-emitting diodes is still in its infancy,and its stability and efficiency have yet to be further improved.In this thesis,the perovskite light-emitting diodes with different color emission were achieved by adjusting the components in its precursor.Firstly,we introduced Cs into the organic-inorganic hybrid quasi-2D perovskite PEA2(MAPbBr3)n-1PbBr4 and increased the MABr content in it.The experimental results show that this method can improve the coverage of the quasi-two-dimensional perovskite film and reduce the grain size of the perovskite.Combining these two modification methods,the green light PeLED was prepared and its max luminance was increased from 4000 cd/m2 to 8000 cd/m2,and the current efficiency from 4.4 cd/A to 5.9 cd/A.Subsequently,in order to reduce the environmental pollution of PeLEDs,we replaced part of the lead with non-toxic SrCl2 in PEA2(CsPbBr3)n-1PbBr4.We found that the surface morphology of the perovskite film based on SrCl2 was more compact and had better thermal stability.Since the Sr ion has a smaller ionic radius than the Pb ion,when the ratio is the same,the SrCl2 based perovskite has a bluer photoluminescence peak than PbCl2.The quasi-2D blue PeLEDs prepared by doping 37%SrCl2 has an EL peak position of 478 nm and a maximum current efficiency of 2.06 cd/A,which is far superior to the performance of PbCl2-based perovskite light-emitting device under the same doping ratio..Finally,based on the SrCl2 doped blue PeLEDs,CsI was added to prepare a single-emitting layer white perovskite light-emitting device with Cl,Br,I tri-halogen mixed.We found that SrCl2 can effectively inhibit the transfer of halide ions in perovskite.The white PeLEDs we obtained can achieve luminance of 155 cd/m2,current efficiency of 0.17cd/A,and CIE of(0.32,0.32)driven by a low voltage of 5.5V.It provides a new idea for the application of perovskite materials in white light devices.