High‐Efficiency Red Organic Light‐Emitting Diodes with External Quantum Efficiency Close to 30% Based on a Novel Thermally Activated Delayed Fluorescence Emitter

Abstract

Researchers have spared no effort to design new thermally activated delayed fluorescence (TADF) emitters for high‐efficiency organic light‐emitting diodes (OLEDs). However, efficient long‐wavelength TADF emitters are rarely reported. Herein, a red TADF emitter, TPA–PZCN, is reported, which possesses a high photoluminescence quantum yield (ΦPL) of 97% and a small singlet–triplet splitting (ΔEST) of 0.13 eV. Based on the superior properties of TPA–PZCN, red, deep‐red, and near‐infrared (NIR) OLEDs are fabricated by utilizing different device structure strategies. The red devices obtain a remarkable maximum external quantum efficiency (EQE) of 27.4% and an electroluminescence (EL) peak at 628 nm with Commission Internationale de L'Eclairage (CIE) coordinates of (0.65, 0.35), which represents the best result with a peak wavelength longer than 600 nm among those of the reported red TADF devices. Furthermore, an exciplex‐forming cohost strategy is adopted. The devices achieve a record EQE of 28.1% and a deep‐red EL peak at 648 nm with the CIE coordinates of (0.66, 0.34). Last, nondoped devices exhibit 5.3% EQE and an NIR EL peak at 680 nm with the CIE coordinates of (0.69, 0.30).

Rational design of perfectly oriented thermally activated delayed fluorescence emitter for efficient red electroluminescence

“…6e and Table 2). These values are among the best EL performance for red TADF OLEDs [39][40][41]. It is also noted the resulting OLEDs suffer from severe efficiency roll-off at high luminance, which can be alleviated by optimizing doping concentration of both emitters in the host matrix ( Fig.…”

Harvesting triplet excitons for near-infrared electroluminescence via thermally activated delayed fluorescence channel

“…And the recent works indicate that the efficient RISC process also highly relies on the considerable spin-orbital coupling between the relatively excited states, which is dependent on the heteroatom in the molecular skeleton ( Samanta et al., 2017 ; Guo et al., 2020 ). The twisted D-A structure has been demonstrated very effective in the visible region ( Lin et al., 2016 ; Zeng et al., 2018 ; Chen et al., 2018 ; Zhang et al., 2019 ). The extraordinary device efficiency achieved in the visible region also encourages researchers to construct TADF emitters with efficient NIR emission.…”

A simple and efficient approach toward deep-red to near-infrared-emitting iridium(iii) complexes for organic light-emitting diodes with external quantum efficiencies of over 10%

“…Due to their great potential for applications in photodynamic therapy, signal processing, night-vision devices and information-secured displays, near-infrared (NIR) light-emitting organic materials and their devices have aroused growing interest recently. [1][2][3][4] Thermally activated delayed uorescence (TADF) organics [5][6][7][8] and transition metal based phosphors, [9][10][11] which convert both 25% singlet and 75% triplet excited states into light emissions, are commonly used to achieve efficient NIR emitters. It is a real challenge to attain NIR organic light-emitting diodes (NIR OLEDs) with external quantum efficiencies (EQEs) of over 10% due to the lack of efficient NIR emitters.…”