Versatile boron‐based thermally activated delayed fluorescence materials for organic light‐emitting diodes

Abstract

During the last few years, organoboron‐based thermally activated delayed fluorescence (TADF) materials have received extensive attention in optoelectronic area, owing to the unique electronegativity of boron atom. Herein, many research progress of organoboron‐based TADF materials for organic optoelectronic devices is summarized. This review comprehensively documents the organoboron‐based TADF materials according to the emission colors from blue to red‐near‐infrared (red‐NIR), covering the molecular design strategies, photophysical properties, and optoelectronic performance in organic light‐emitting diodes (OLEDs). The current progress and future challenges in this fast‐growing fields are reviewed systematically, providing instructive guidance for the future research on high‐performance TADF‐OLEDs.

NIR TADF emitters and OLEDs: challenges, progress, and perspectives

“…[64] Recently, TADF materials with polycyclic heteroaromatics embedded in multiple boron (B)-and nitrogen (N)-atoms have been also developed. [65][66][67] Introduction of multiple B and N This journal is © The Royal Society of Chemistry 20xx…”

“…64 Recently, TADF materials with polycyclic heteroaromatics embedded in multiple boron (B)-and nitrogen (N)-atoms have also been developed. [65][66][67] Introduction of multiple B and N atoms into polycyclic heteroaromatics resulted in the successful formation of restricted p-bonds on the phenyl-core for delocalized excited states, thus narrowing the energy gap. As the rst NIR multi-resonance TADF emitter developed in 2021, the R-TNB (Scheme 3) based OLED exhibited an impressive high maximum EQE of 27.6%; the value is the highest recorded among all reported results of NIR TADF devices as summarized in Table 2.…”

Rational design of orange-red iridium(iii) complexes by an isomer engineering strategy for improved performance of white organic light-emitting diodes

“…On account of its high T 1 energy of 2.8 eV, the extensively used p-type material TCTA was chosen as the electron-blocking material. 58,59 At the same time, its HOMO energy level lies between TAPC and 26DCzPPy, which helped in reducing the HOMO energy barrier and preventing the diffusion of triplet excitons from 26DCzPPy to the neighboring HTL, thus improving exciton utilization. 60,61 Besides, 26DCzPPy was chosen as the host material in the device with its well-known bipolar transporting feature and relatively high T 1 energy level (2.71 eV), which is favorable for efficient energy transfer from the host to the iridium(III) guest.…”

Rational molecular design of TADF emitters towards highly efficient yellow electroluminescence with a nearly 30% external quantum efficiency and low roll-off

“…In recent years, purely organic thermally activated delayed fluorescence (TADF) emitters have been extensively explored in light of their metalfree properties and the ability to harvest both singlet and triplet excited states via an efficient upconversion process for light emission, which can achieve a theoretical 100% exciton utilization. [6][7][8][9][10][11][12] TADF emitters based on the donor-acceptor (D-A) structure feature a small singlet-triplet splitting (DE ST ) for efficient reverse intersystem crossing (RISC) from the triplet to the singlet state. 7 Typically, a large twisting angle between the D and A units can result in effective spatial separation of the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) to enable a small DE ST , thus promising excellent TADF characteristics.…”

“…In recent years, purely organic thermally activated delayed fluorescence (TADF) emitters have been extensively explored in light of their metal-free properties and the ability to harvest both singlet and triplet excited states via an efficient upconversion process for light emission, which can achieve a theoretical 100% exciton utilization. 6–12…”