Study On Doping Of Quasi-2D Perovskite Thin Films And Photoelectric Characteristics Of PeLED Devices

Perovskite is a very popular material in recent years,which has very important applications in various fields.Perovskite has excellent photoelectric properties,such as high color purity,adjustable color,high fluorescence quantum yield.These advantages promote the application of perovskite in electroluminescent devices.Perovskite light-emitting diode（PeLED）with perovskite as the light-emitting layer has been greatly improved in recent years.However,the three-dimensional perovskite exciton has low binding energy and high carrier mobility,which is not conducive to the carrier radiation recombination luminescence in perovskite and hinders the further improvement of PeLED device efficiency.In this case,the quasi two-dimensional perovskite has come into people’s view.Its self-assembled quantum well structure can limit the carrier activity,improve the exciton binding energy and reduce the carrier mobility.However,the number of perovskite layers in the long chain organic spacer cations of quasi-two-dimensional perovskite is usually not single,which leads to the decrease of luminous efficiency.In addition,the decrease of the grain size of quasi-two-dimensional perovskite will lead to the increase of surface defects and increase the probability of non radiative recombination.At the same time,the lead element in perovskite will cause harm to human body and ecological environment.Reducing or eliminating the lead content in perovskite is very important for the commercial application of PeLED devices.Therefore,the content of this paper is mainly based on the quasi two-dimensional perovskite PEA₂Cs_n-1Pb_nBr_3n+1film and the corresponding PeLED device performance research,to improve the surface morphology of the film,improve the performance of PeLED,and reduce the lead contentFirstly,according to the chemical expression of PEA₂Cs_n-1Pb_nBr_3n+1,the molar ratios of Pb Br₂,Cs Br and PEABr were adjusted to prepare PEA₂Cs_n-1Pb_nBr_3n+1 thin films with different n values,and three-dimensional perovskite Cs Pb Br₃thin films were prepared.The morphology of quasi two-dimensional perovskite film is better than that of three-dimensional perovskite film,and the smaller the n value is,the better the surface morphology is.In the case of n=3,that is,PEA₂Cs₂Pb₃Br₁₀ has the best device performance,with the on-off voltage of 4 V,the maximum brightness of 917 cd/m² and the maximum EQE of 1.59%.It provides the basis for the follow-up experimental research.Then,on the basis of determining the best performance of PEA₂Cs₂Pb₃Br₁₀ as thelight-emitting layer of PeLED device,adding a small amount of small molecular organic matter m CP into PEA₂Cs₂Pb₃Br₁₀ can passivate the surface defects of PEA₂Cs₂Pb₃Br₁₀,reduce or disappear the two-dimensional structure in quasi two-dimensional perovskite and quasi two-dimensional structure with two layers,and improve the quality of the film.The results show that the maximum brightness increases from 238 cd/m² to 596 cd/m²,the maximum current efficiency increases from 4.25 cd/A to 7.99 cd/A,and the maximum EQE increases from 1.72%to 3.34%.Secondly,a small amount of DMAC-DPS was added into Cd Se/Zn S quantum dots,DMAC-DPS could improve the surface morphology of QDs films,and the maximum current efficiency of QLED devices increased from 0.86 cd/A to 3.25 cd/A,and the maximum EQE increased from 0.64%to 2.27%.Finally,the effect of metal ions doping on the quasi-two-dimensional perovskite is studied.When Mg²⁺is added into PEA₂Cs₂Pb₃Br₁₀,Mg²⁺can partially replace Pb²⁺in PEA₂Cs₂Pb₃Br₁₀,and the crystal structure of the quasi-two-dimensional perovskite is changed.Meanwhile,the part with smaller layers in the quasi two-dimensional perovskite is relatively more.The results show that the EL peak of PeLED is blue shifted and the half peak width becomes wider.