Back Migration Based Long Lifetime Approach for Organic Light‐Emitting Diode

Abstract

Lifetime is one critical reliability issue in electronics, especially in organic devices including organic light emitting diodes (OLEDs), solar cells, thin film batteries, thin film transistors, and memories, etc. Many causes that contribute to device failures have been found out. So far, several methods for improvement in the device lifetime have been proposed, albeit effective approaches are still under developing and the ideal will be the one that enables cost-effective fabrication with ease of processing. Here an easy-toapply method based on the back migration to improve the lifetime of OLED as well as LED devices are presented. That is done by simply applying a reverse bias voltage with an appropriate magnitude. For example, lifetime of a studied white OLED device at 9500 cd m À2 can be increased from 288 to 685 h, an increment of 137%, as a reverse bias of 10 V is applied to the pristine device for 2 h. It can be further increased to 857 h, an increment of 197%, as the reverse bias is kept for 4 h. The lifetime can still be improved for non-pristine devices.

Unraveling Degradation Processes and Strategies for Enhancing Reliability in Organic Light-Emitting Diodes

“…The oxidation of Ag at the anode into Ag + cations, which subsequently migrate through the electric field and are electrochemically reduced back to zerovalent metal when they come into contact with the cathode, is one proposed mechanism [115]. Some systems are mainly produced by momentum transfer from moving charge carriers to metal atoms, which are subsequently pushed forward by an "electron wind" or "hole wind" [116,117]. To distinguish it from electrochemical migration, this latter mechanism is called electromigration.…”

Organic Light-Emitting Diodes with Ultrathin Emitting Nanolayers

“…Similar to conventional OLEDs, UEN-based OLEDs also suffer from water and oxygen attack, electrochemical and photochemical reactions, electrical and thermal breakdown, etc. [170][171][172][173][174]. However, compared to conventional devices, UEN-based OLEDs may be more influenced by electron-induced molecule migration.…”

Approaches for Long Lifetime Organic Light Emitting Diodes

“…In OLEDs, due to the continuous flow, electrons collide each other, which leads to molecular migration, resulting in the loss of device efficiency and a decrease in lifetime. [134,135] According to Shen et al mobile ions induced voltage changes, leading to device degradation. [136] According to Probst et al, if the metal/organic layer interaction is feeble in the interface, it will enhance the metal migration.…”

“…In OLEDs, due to the continuous flow, electrons collide each other, which leads to molecular migration, resulting in the loss of device efficiency and a decrease in lifetime. [ 134,135 ] According to Shen et al. mobile ions induced voltage changes, leading to device degradation.…”