Understanding of the aging pattern in quantum dot light-emitting diodes using low-frequency noise. Issue 29 (22nd July 2020)

• Record Type: Journal Article
• Authors: Lee, Kookjin; Yun, Jinyoung; Lee, Suhyeon; Song, Jaeick; Kim, Yeonsu; Kwak, Jeonghun; Kim, Gyu-Tae
• Is Part Of: Nanoscale. Volume 12:Issue 29(2020)
• Page Start: 15888
• Page End: 15895
• Publication Date: 2020-07-22
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/d0nr01885f
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : The negative and positive aging effects of quantum dot (QD) light-emitting diodes (QLEDs) have received considerable attention in recent years and various analysis methods have been discussed. Abstract : The negative and positive aging effects of quantum dot (QD) light-emitting diodes (QLEDs) have received considerable attention in recent years and various analysis methods have been discussed. Here, we introduce a new approach to understand the aging effect of QLEDs, which is to diagnose the behavior of carriers and traps at interfaces between each layer of the QLEDs and inside the layers themselves. In particular, low-frequency noise (LFN) measurement and the analysis of current in the QLEDs were introduced to investigate the trapping/de-trapping behaviors of carriers in the defect states in the devices. A flicker noise was observed before the carriers are injected into the QD emitting layer, while the exciton generation–recombination (G–R) noise and shot noise were observed when the electrons were injected. A correlated noise, which is the correlated model of the trapping/de-trapping of the carriers near and/or inside the QDs and the exciton recombination, was also observed above the turn-on voltage. In addition, when the devices were aged with a constant current source, rapid increases in the luminance and external quantum efficiency (EQE) were observed for up to 50 h. After 100 h of the current aging, however, the devices were negatively aged with the reduced EQE. The LFN analysis results imply that the aging phenomena mainly depend on the trapping/de-trapping of carriers. In addition to the LFN analysis, we also investigated the current density–voltage–luminance and capacitance–voltage characteristics of the devices to clarify the aging behaviors in QLEDs.