Using Different Defect Passivation Methods To Improve The Efficiency Of Perovskite Light-emitting Devices

In recent years,as a new research direction in the field of energy and materials,they are widely used in optoelectronic devices such as solar cells and light-emitting devices,photodetector and laser,the exploration and research of perovskite materials has advanced rapidly.This is due to the enticing characteristics of perovskite materials such as high light absorption coefficients,less non-radiative recombination,convenient solution-processing and lower carrier trap density.Defect recombination in the perovskite film is one of the main factors affecting the efficiency and stability of the device.Intrinsic defects in the perovskite film can be passivated by introducing additives.Alternatively,the method of interfacial modification can effectively reduce defects in the perovskite thin film,thereby improving the radiation recombination efficiency and device stability in the perovskite light-emitting device.These is mainly studies the effects of the post-treatment with TPBi solution on the crystal structure,surface morphology,photophysics,and carrier transport characteristics of the perovskite film.It was found that the morphology and crystallinity of the samples did not change significantly with the variation in TPBi concentration.Additonal diffraction peaks at 21.4°,34.2°,37.3°,and 43.4°,coming from the(110),(210),(122),(220)crystal facets emerges in the XRD diffractogram of the sample post-treated with TPBi solution.Post-treatment with TPBi solution increases the PL intensity,which increased with the increase of TPBi concentration.In order to investigate the effect of the TPBi post-treatment the density of defect states of perovskite films,the transient lifetimes of MAPb Br3 and TPBi-treated perovskite films were measured.The transient lifetime of MAPb Br3 perovskite films was 13.33 ns and the concentration was 1mg/ml of TPBi solution-treated MAPb Br3 thin film show PL transient life of 49.05 ns,at the same time the sample with the configuration of MAPb Br3/evaporated TPBi layer show the PL transient life of 17.37 ns.The experimental results indicate that the post-treatment with TPBi solution can effectively passivate defects on the surface and grain boundaries of the perovskite film and promote the rate of radiative recombination.Analysis of hole-dominated device shows the holeblocking effect of the TPBi layer on hole transport.The effect of organic additive TPBi concentration on the luminous brightness,luminous efficiency and electroluminescent spectral stability of the device was studied.The luminous efficiency of the sample using CB rapid crystallization was 19.7cd/A,and the EQE was 5%.Light-emitting devices with TPBi post-treatment show the luminous efficiency was 39.2 cd/A,and the EQE of 9.9%,which are 2.0 times those of the devices without TPBi-treatment.Therefore,we studied the surface morphology,crystal structure,photophysics,and electroluminescence characteristics of DJ quasi-two-dimensional perovskites containing diaminobutane cations.Compared with MAPb Br3 perovskite film,quasi-two-dimensional perovskite film with BDADBr diamine molecule introduced the grain size is decreased.This is attributed to the fact that BDADBr,which cannot be accommodated in the [Pb Br6]4-lattice,terminates the further crystal growth.The MAPb Br3 sample shows diffraction peaks at 14.9°,21.2°,30.1°,33.8°,37.0°,and 43.1°,which are assigned to respective(100),(110),(200),(210),(112),and(220)crystallographic planes of the MAPb Br3 cubic crystal structure.The 2:1 sample shows pronounced diffraction peaks at 9.0°,12.3°,16.7°,18.0°,27.1°,and 28.9°,originating from the(0k0)crystal planes of the lowdimensional perovskite phases with different numbers of inorganic layers(n),respectively.The PL spectrum of the 2:1 sample measured from the film side resembles that measured from the substrate sides,revealing relatively homogeneous distribution of the phases with different n values.The PL intensity increases with increasing BDADBr content.The PL maximum wavelength of the thin films made of this material is blue-shifted by 30-40 nm after the introduction of tetramethylene diamine bromate and the photoluminescence quantum yield is enhanced simultaneously.Related sky-blue perovskite light-emitting diodes show a maximum external quantum efficiency of 1.0% and a luminance efficiency of 1.6 cd/A.