Recent Progress of the Lifetime of Organic Light‐Emitting Diodes Based on Thermally Activated Delayed Fluorescent Material

Abstract

that satisfy the physical parameters of the OLEDs, and this could be assisted by the use of organic materials. Therefore, organic materials have played a key role in extending the lifetime of OLEDs. In particular, host materials and emitters in the emitting layer have been the major contributors to the improved lifetime of OLEDs, although charge transport materials such as hole and electron transport materials, exciton blocking materials, and carrier injection layers have also supported their extended lifetime. The advance in the lifetime of PhOLEDs has been dominantly assisted by the host materials, while that of TADF OLEDs has been mostly assisted by the emitters. Particularly, among several different types of host materials, the TADF-type hosts were the most effective hosts for long lifetime in the PhOLEDs. Therefore, TADF materials have played a decisive role in the development of highly efficient and long lifetime OLEDs.This progress report discusses the contribution of TADF materials toward the lifetime improvement of PhOLEDs as hosts and TADF OLEDs as emitters. The material design and device performances of the TADF materials are mainly examined based on recent studies that include the long lifetime PhOLEDs and TADF OLEDs assisted by TADF materials. The material designs of the intermolecular-type TADF hosts, the intramolecular-type TADF hosts, and the intramolecular-type TADF emitters for both high efficiency and long lifetime are widely covered in this report. Moreover, future possibilities of the TADF materials as hosts and emitters for long lifetime OLEDs are also proposed. The application of the TADF materials is summarized in Figure 1. Recently, the external quantum efficiency and lifetime of organic light-emitting diodes (OLEDs) have been dramatically upgraded due to development of organic materials and device structure. In particular, an intramolecular or intermolecular complex based on thermally activated delayed fluorescent (TADF) materials has greatly contributed to improving OLED device performance. Although high external quantum efficiency has been the main objective of the development of TADF materials as hosts and emitters, recent interest has been directed towards the lifetime of TADFmaterial-based OLEDs. For the past several years, remarkable advances in the lifetime of phosphorescent and TADF OLEDs have been made using TADF materials as hosts or emitters in the emitting layer. Therefore, since TADF materials are useful as both hosts and emitters for a long lifetime, this work discusses the recent progress made in developing TADF materials for long-lifetime OLEDs.

Revealing the Cooperative Relationship between Spin, Energy, and Polarization Parameters toward Developing High‐Efficiency Exciplex Light‐Emitting Diodes

“…Singlets and triplets are allowed and forbidden to recombine, respectively, due to spin selection rule. It has been shown that the triplets can be almost 100% converted into singlets in thermally activated delayed fluorescence (TADF) molecules based on the design of chemically combining donor and acceptor moieties to enable intramolecular charge‐transfer states . Recently, various TADF‐molecule‐based OLEDs with extremely high external quantum efficiency (EQE) exceeding 35% have been successfully demonstrated .…”

Femto- to Millisecond Time-Resolved Photodynamics of a Double-Functionalized Push–Pull Organic Linker: Potential Candidate for Optoelectronically Active MOFs

“…The idea was to reduce the energy gap between the singlet and triplet excited states, favouring the process known as thermally activated delayed fluorescence (TADF). The aforementioned linker was used in the synthesis of a Zr-based MOF, which retains the TADF properties of the linker, having this special importance for its promising potential to be applied in the next generation of light-emitting diodes [26,27].…”

Negative Charge Management to Make Fragile Bonds No Longer Fragile towards Electrons for Robust Organic Optoelectronic Materials

“…The intrinsic degradation of OLEDs is mainly ascribed to the chemical deterioration of organic (or metal-organic) materials. [4][5][6][7][8][9] Many undesired (photo)physical processes could induce such chemical deterioration, like exciton−polaron and exciton−exciton annihilations (EPA and EEA), in which EPA has been confirmed as a dominate mechanism. [10][11][12][13][14][15][16] In this process ( Fig.…”