Molecular Design Strategy of Organic Thermally Activated Delayed Fluorescence Emitters

Abstract

Recently, organic thermally activated delayed fluorescence (TADF) emitters have attracted a great deal of attention because they can theoretically realize 100% internal quantum efficiency. Many TADF emitters have been developed since the first demonstration of close to 20% external quantum efficiency in the devices. Recently developed TADF emitters demonstrated close to 37% external quantum efficiency in blue, above 30% external quantum efficiency in green, and close to 18% external quantum efficiency in red devices. Therefore, TADF organic light-emitting diodes could potentially be substituted for high-efficiency phosphorescent organic light-emitting diodes. In this work, we reviewed molecular design strategies of organic-based TADF emitters by classifying them into several categories depending on the material parameters required for the TADF emitters. In addition, we proposed a future development direction of TADF emitters to make them competitive with phosphorescent emitters.

Effect of Carrier Balance on Device Degradation of Organic Light‐Emitting Diodes Based on Thermally Activated Delayed Fluorescence Emitters

“…[4] Furthermore, Zhang et al reported that a device architecture using a gradually doped EML in blue phosphorescent OLEDs can achieve a tenfold increase in the device lifetime because of the resulting control of the emission zone and the triplet exciton density inside the EML. [11][12][13][14] To suppress unwanted interactions between the triplet excitons and quenching species such as trapped charge carriers, the triplet exciton lifetime of the emitters should be managed carefully because the rates of the exciton annihilation processes are critically dependent on the triplet exciton density. [11][12][13][14] To suppress unwanted interactions between the triplet excitons and quenching species such as trapped charge carriers, the triplet exciton lifetime of the emitters should be managed carefully because the rates of the exciton annihilation processes are critically dependent on the triplet exciton density.…”

Effect of a Pendant Acceptor on Thermally Activated Delayed Fluorescence Properties of Conjugated Polymers with Backbone‐Donor/Pendant‐Acceptor Architecture

“…The maximum EQE of the device based on PCzA3PyB5 is clearly inferior to those of PCzAB2Py5 and PCzAB3Py5, despite exceeding the theoretical limit of conventional fluorescent OLEDs. This result is reasonable owing to the lack of phenyl linker between donor and acceptor in PCzA3PyB, leading to the low PLQYs, although their devices have relatively low turn‐on and driving voltages . By contrast, the devices containing PCzAB2Py and PCzAB3Py with a phenyl linker achieve better EL performances, in particular, the very slow roll‐offs of EQE at high luminance.…”

Recent progress of pyrimidine derivatives for high-performance organic light-emitting devices

“…[11][12][13] Recently, thermally activated delayed fluorescence (TADF) emitters based on pure organic compounds have been considered as an alternate technology to phosphorescent counterparts to realize an IQE of 100%. [14][15][16][17][18][19][20][21][22][23][24][25] Until recently, several TADF OLEDs have achieved a high EQE of over 30% at maximum. [26][27][28][29][30][31][32] The efficiency of the TADF-based OLEDs is expected to exceed that of OLEDs based on phosphorescent emitters due to the unlimited molecular design of pyrimidine derivative-based TADF emitters.…”