Font Size: a A A

Study On Efficiency Improvement Methods And Modulation Characteristics Of Perovskite Quantum Dot LEDs

Posted on:2022-11-05Degree:MasterType:Thesis
Country:ChinaCandidate:C Y TangFull Text:PDF
GTID:2518306758989879Subject:Circuits and Systems
Abstract/Summary:PDF Full Text Request
Perovskite quantum dots are suitable as emission layer to fabricate high-efficiency LEDs due to their low cost,simple preparation,narrow emission linewidth(<100 me V),and high fluorescence quantum yield.High-efficiency LEDs have great application potential in the field of visible light communication.At present,most of the perovskite LEDs used for visible light communication are based on photoluminescence.The preparation process of photoluminescence LEDs is simple,but its luminous efficiency is not high,the luminance is low,and the energy consumption is large.The use of electroluminescence can directly emit in the emission layer,improve the luminous efficiency and luminance of the device,and meet the green concept of energy saving,low carbon and environmental protection.It should be noted that the performance of perovskite quantum dot LEDs in electroluminescence mode is usually related to the perovskite material and device structure.During the purification process,there are a large number of vacancy defects formed on the surface of perovskite quantum dots due to the shedding of surface ligands,which leads to a decrease in the fluorescence quantum yield of the quantum dots.Moreover,as the ligands commonly used in perovskite quantum dots,oleylamine and oleic acid have a large steric hindrance due to the long carbon chain,which forms an insulating layer on the surface of the quantum dots,hindering the transport of carriers in the pertovskite layer in optoelectronic devices.Also,the exciton quenching of perovskite light-emitting diodes is caused by the unbalanced injection in perovskite layer,resulting in the reduction of the device performance.Based on the above considerations,we improved the efficiency of electroperovskite LEDs by optimizing the luminescent properties of the emission layer materials and improving the carrier balance of the device from the aspects of materials and device physics,and then explored their modulation characteristics.The main research of this paper are as follows:(1)From the perspective of optimizing the photoelectric properties of the emitting layer materials,we adopted short chain organic ligand p-iodine-d-phenylalanine(PIDP)to post treat Cs Pb I3 QDs.By partially replacing ligands such as oleamine and oleic acid,the conductivity of perovskite QD films was improved,so as to promote the carrier transport of light-emitting layer of LED devices.At the same time,the electron mobility and hole mobility of perovskite nanocrystalline films were reduced,and the injection balance of carriers in the light-emitting layer was improved.Moreover,PIDP effectively passivated the defects on the perovskite surface,which improved its PLQY.Finally,we prepared perovskite LED devices with external quantum efficiency of 12.4%and maximum luminous brightness of 2000 cd m-2.(2)From the perspective of device physical engineering,in order to improve the carrier injection balance of the light-emitting layer of perovskite LED devices,the carrier mobility of the device transport layer material needs to be adjusted appropriately.Doping Co into Zn O reduced the electron mobility of Zn O,which improved the carrier injection balance of Cs Pb I3 QD LED.Meanwhile,the exciton quenching phenomenon at the interface between Zn O and the emitting layer was suppressed,and the luminous efficiency of perovskite light-emitting layer was effectively improved.In addition,Co doped Zn O improved the film-forming property of perovskite light-emitting layer and facilitated the preparation of high-efficiency LED devices.Finally,the external quantum efficiency(EQE)of Cs Pb I3 QD LED was increased by 70%,and the maximum brightness was increased from 867 cd m-2of the original device to 1858 cd m-2.In addition,by inserting polyethyleneimine between Co doped Zn O layer and perovskite light-emitting layer,EQE of LED was further improved to13.0%,because polyethyleneimine can passivate the surface defects of perovskite.(3)Based on the above work,the modulation bandwidth of Cs Pb I3LED with PIDP post-processing and Cs Pb I3 perovskite QD LED utilizing Co doping on Zn O electron transport layer were tested respectively.The results showed that the modulation bandwidth of the LED increased from1.6 to 3.8 MHz after PIDP post-treatment.The reason is that the working current density of Cs Pb I3 increases after PIDP,which increases the probability of loading current recombination.Therefore,the modulation bandwidth of the device was significantly improved.The modulation bandwidth of Cs Pb I3 QD LED utilizing Co doping on Zn O electron transport layer was reduced from 600 to 300 k Hz.Through the time-resolved photoluminescence spectrum of the emitting layer,it was found that the average lifetime of the emitting layer increased after Co doping,which is caused by the fact that Co doping effectively suppresses the exciton quenching at the interface between the light-emitting layer and the electron transport layer.
Keywords/Search Tags:Perovskite quantum dots, light-emitting diodes, emission layer, transport layer, modulation bandwidth
PDF Full Text Request
Related items