Investigation On The Transient Process Of Inverted Quantum Dot Light Emitting Diodes

In recent years,with the continuous development of science and technology,people's growing material and cultural needs require the display technology to improve greatly.Since the Alivisatos's group used colloidal quantum dots?QD?as the light-emitting layer and proposed quantum dot light-emitting diodes in 1994,QD has attracted wide attention because of its excellent photoelectric characteristics,such as adjustable emission wavelength and high color purity.There for,the quantum dot light emitting device?QLED?has many unique advantages such as high saturated color,excellent flexibility,and low cost.So it is known as a potential next-generation display technology.QLED has experienced nearly thirty years of development,and its progress is remarkable,but still need to improve.Now the external quantum efficiency?EQE?of red and green QLED devices has exceed 20%,and the lifetime of red QLED at a brightness of 100 cd/m² can be as long as 2200000 hours,which has meet the needs of some commercial applications.Green and blue QLED performance has been greatly improved,but there is still a gap from commercial applications.At present,high-performance QLEDs are mostly based on quantum dots containing heavy metal element like cadmium as the light-emitting layer.It is not only harmful to the human body,but can also cause serious pollution to the environment,which greatly limits its commercial applications.And there is still a big gap between the performance of non-toxic quantum dot devices as alternatives.In order to achieve efficient and stable QLED,we need to have more in-depth study of the device's mechanism,guiding us to further optimize the device structure and improve device performance.In this paper,we proposed a method for testing the transient electroluminescent process of quantum dot light-emitting devices and used it to study the transient process of a device based on non-toxic CuInS₂ quantum dot.And then,we analyze the mechanism of PEIE modified device,which improve the performance of the device.The main contents of this article are as follows:1.We introduced the research progress and existing problems of QD and QLED in detail.Then we designed a test method combining transient electroluminescence test and photoluminescence test technology,introduced the principles of each part of the entire test system in detail.It can be used to analyze the carrier dynamics process such as carrier transport,charge accumulation and trapping in the device,so that we can study the mechanism of quantum dots light-emitting in the device.2.Using the test method we designed,the mechanism by which the PEIE layer improves the performance of the QLED device is studied.After analyzing the fluorescence lifetime of the quantum dots at different times during the transient test,we found that the addition of PEIE layer with appropriate thickness can balance the carrier injection inside the device,reduce the charge accumulation inside the device,and modify the ZnO/QD interface to reduce the surface defects of ZnO quench the excitons in the QD,so they can effectively improve device performance.