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Deep red (DR) and near-infrared (NIR) fluorescent emitters are often plagued by design difficulties due to the strong intramolecular interaction. Herein, two new DR and NIR molecules, 4-(7-(10-ethyl-10 H -phenoxazin-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)- N,N -diphenylaniline (TPAC2) and 4-(9-(10-ethyl-10 H -phenoxazin-3-yl)naphtho[2,3-c][1,2,5]thiadiazol-4-yl)- N,N -diphenylaniline (TPANZC2), characteristic with hybrid local and charge transfer were achieved via iteration with a theoretical combined experimental method. Both emitters realized the reverse intersystem crossing (RISC) via the hot exciton channel. As results, the non-doped organic light-emitting diodes (OLEDs) of TPAC2 and TPANZC2 achieved the maximum external quantum efficiency (EQE max) of 2.4% at 680 nm and 1.1% at 755 nm, respectively. Both conspicuous upward EQE curves demonstrated excellent resistance to efficiency roll-off. The ternary co-doping system further unleashed the potential in NIR emission, the co-doped device with 5 wt% TPANZC2 achieved an EQE of 4.6% with emission at 724 nm, which is among the best results of HLCT-NIR fluorescent OLEDs to date. [Display omitted] • Iterative strategy reasonably achieved deep red to NIR emission. • The co-doped NIR device achieved an EQE of 4.6%, is the best HLCT-NIR OLED performance to date. • EQE loss only 2.4% and 0.8% at 90% maximum luminescence. [ABSTRACT FROM AUTHOR]

This work provides a flexible and convenient method for fine-tuning the excited states of emitters, precise "surgery" was performed by targeting the molecular excited states through locally large twisted conformations, and finally obtained excellent hot exciton red emitters and high efficiency non-doped deep-red OLEDs. [Display omitted] • Deep-red emitters construct idea utilizing locally large twisted conformation. • Three emitters display hot exciton and aggregation-induced emission properties. • Breakthrough EQEs of hot exciton non-doped red devices up to 5.3% and 6%. The precise regulation of excited state is a challenge to emitters for achieving highly efficient non-doped deep-red electroluminescence (EL). Herein, we used triphenylamine and phenoxazine as donors and benzo[c][1,2,5]thiadiazole as an acceptor to construct a hot exciton skeleton. Then chemically modified the phenoxazine by locally large twisted conformation to obtain N , N -diphenyl-4-(7-(10-phenyl-10H-phenoxazin-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)aniline (TPAPH), 4-(7-(10-(4-ethoxyphenyl)-10 H -phenoxazin-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)- N , N -diphenylaniline (TPAPHOC2), and 4-(3-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)-10 H -phenoxazin-10-yl)benzonitrile (TPAPHCN), thereby achieving excited state perturbation. As a result, three emitters exhibited aggregation-induced emission enhancement and hybridized local and charge transfers characteristics based on photophysical experimentals. In EL, the TPAPH-, TPAPHOC2-, and TPAPHCN-based non-doped devices achieved deep-red emission with Commission International de L'Eclairage coordinates of (0.68, 0.32), (0.69, 0.31), and (0.66, 0.34) and with emission peaks at 660, 669, and 647 nm, respectively. The maximum external quantum efficiencies were 5.3%, 3.7%, and 6.0%, respectively. The results of this study not only realize the non-doped deep-red OLEDs with high performance but also indicate that the presence of locally large twisted conformation presented an efficient manner for exploring precise excited state tuning for fluorescent emitter. [ABSTRACT FROM AUTHOR]