Optimization Of Luminescent Layer And Hole Transport Layer In CsPbBr₃ Light Emitting Diodes

All inorganic perovskite materials as a new type of materials in recent years,it has a series of excellent optical and electrical properties,such as high color purity,high carrier mobility,tunable band gap,high photoluminescence quantum yield.Compared with the organic-inorganic hybrid perovskite,its stability has been greatly improved and broader application prospect.However,all inorganic perovskite films often have poor film-forming properties and the prepared films have a large number of pinholes and defects,which greatly limits the use of materials,the large current leakage of the light-emitting device also reduces the luminous efficiency of the device.In addition,poly(3,4-ethylenedioxythiophene)(styrene sulfonate)(PEDOT:PSS)is widely used in light-emitting diode devices as a hole transport layer to usedue to the large energy barrier between the hole transport layer and the light-emitting layer,But the imbalance of electron and hole injection in light-emitting diode devices will have a negative effect on the performance of light-emitting devices.This paper mainly describes from two parts:1.Three kinds of trimethylamines with different chain lengths were doped into the Cs Pb Br₃films,and their effects on Cs Pb Br₃films were investigated.Finally,hexyltrimethylammonium bromide(HTAB)with appropriate chain length was selected as the additive of Cs Pb Br₃film.The Lewis acid-base reaction between HTAB and perovskite can connect the dispersed and discontinuous perovskite,which increases the coverage of the film and effectively reduces the defect state of the film.The doping of HTAB also reduced the original large grain size,increased the exciton binding energy in perovskite and improved the luminescent properties and morphology of the films.HTAB doping also optimizes the crystallization of Cs Pb Br₃thin films,and the density of defect states in the films becomes less,the exciton binding energy in perovskite is increased.Luminescence properties and morphology of the films are improved to a certain extent.Meanwhile,HTAB doping also reduces the density of defect states in the films.The brightness and external quantum efficiency of the initial device are 1498cd/m²and 0.20%,After adjusting the doping concentration and annealing temperature of HTAB,The brightness and external quantum efficiency of the optimized device are5588 cd/m²and 1.55%,which are greatly improved compared with the original device.2.Because the electron injection efficiency in the light-emitting device is much higher than the hole,the carrier recombination imbalance is caused,A strong oxidizing P-type dopant F4-TCNQ is added into PEDOT:PSS,and the injection barrier between the luminescence layer and hole layer is reduced by 0.14 e V.F4-TCNQ also improves the conductivity of PEDOT:PSS and improves the hole transmission capacity.At the same time,the doping of F4-TCNQ did not have a great influence on the hydrophobicity and transmittance of PEDOT:PSS film.Meanwhile,the characterization of the upper perovskite revealed that the doping of F4-TCNQ did not significantly affect the growth of the upper perovskite film,the surface morphology and optical properties of the perovskite film did not change significantly.Finally,a light-emitting diode device with a brightness exceeding 10,000 cd/m²and an external quantum efficiency close to2%was obtained.