A Breakthrough in Solution‐Processed Ultra‐Deep‐Blue HLCT OLEDs: A Record External Quantum Efficiency Exceeding 10% Based on Novel V‐Shaped Emitters

Abstract

It has always been a great challenge to achieve high‐efficiency solution‐processed ultra‐deep‐blue organic light‐emitting diodes (OLEDs) with the Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinates matching the blue primary of Rec. ITU‐R BT.2100, which specifies high dynamic range television (HDR‐TV) image parameters. Inspired by hybrid local and charge transfer (HLCT) excited state emitters improving exciton utilization through high‐lying reverse intersystem system crossing, a series of high‐performance blue emitters by a V‐shaped symmetric D‐π‐A‐π‐D design strategy are developed in this study. Here, the large torsions and unstable bonds of D‐A structures could be improved through π bridges, and also the conjugation length and donor groups can be easily adjusted. The obtained emitters merit excellent photophysical and electrochemical properties, thermal stability, solution processibility, and HLCT excited state excellence. Results suggest that the OLEDs based on the obtained blue emitters all achieve high maximum external quantum efficiency (EQEmax) of more than 8% with very low efficiency roll‐off. In particular, the device based on FIP‐CZ exhibits a satisfactory ultra‐deep‐blue emission (CIEx,y = 0.1579, 0.0387) and a record‐high EQEmax (10.40%) among solution‐processed HLCT‐OLEDs, which is very close to the record EQEmax of devices by vacuum vapor deposition technology.This article is protected by copyright. All rights reserved

Rational design of hybridized local and charge transfer emitters towards deep blue emission by incorporating extra cyano-based acceptor moieties

“…Meanwhile, 2(3phCN)-phCz shows the largest energy difference between T 5 and T 4 , suggesting great reduction of the internal conversion rate, which is beneficial to the utilization of triplet excitons. 32 Consequently, the RISC process is more efficient to enable exciton distribution on S 1 . It should be noted that all the molecules present a relatively high SOC constant (>0.3 cm −1 ) between S 1 and T 5 .…”

A record-high EQE of 7.65%@3300 cd m−2 achieved in non-doped near-ultraviolet OLEDs based on novel D′–D–A type bipolar fluorophores upon molecular configuration engineering

“…Several successful strategies have been proposed to weaken this effect for exploiting D–A-type NUV emitters, for example, incorporating a steric group, introducing a twisted bridge, and utilizing weak electron-donating/accepting groups. Based on these strategies, a series of D–(π)–A type, 41 donor–acceptor–donor (D–A–D) type, 42–45 acceptor–donor–acceptor (A–D–A) type, 46 and donor′–acceptor–donor (D′–A–D) type wide-bandgap organic emitters were reported in doped OLEDs (Fig. 1).…”

Oxygen heterocyclic coumarin-based hybridized local and charge-transfer deep-blue emitters for solution-processed organic light-emitting diodes

“…10 Following this, numerous efficient blue OLEDs boasting high EQE values have been realized based on the HLCT strategy. 11,17–22 However, most of them are developed from nitrogen heterocyclic acceptors, particularly imidazoles, such as benzoimidazole, naphthimidazole, and phenanthro[9,10- d ]imidazole. 23–30 Consequently, developing additional superior acceptors is crucial for broadening HLCT material systems and achieving high-efficiency OLEDs.…”