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Thermally Activated Delayed Fluorescent (TADF) molecules with Donor (D) -Acceptor (A) –Donor-Acceptor π-Conjugated Macrocycle structures have broad application potential in organic light-emitting diodes. In this paper, three D−A line type and one D−A−D−A π‑Conjugated Macrocycle molecules with same donor and acceptor groups are investigated using polarizable continuum model (PCM) combined with density functional theory (DFT) and time-dependent functional theory (TD-DFT) in solvent and film. It is found that the macrocyclic structure has a smaller energy gap (ΔEST) between the first singlet excited state (S1) and the first triplet excited state (T1) than the linear structure. The TADF property is also analyzed based on the calculation of spin–orbit coupling (SOC) and the (reverse) intersystem crossing (RISC) rates between S1 and T1. The macrocyclic molecules have larger SOC and faster RISC rates, which also well explains the experimental predictions and results. [Display omitted] • The macrocyclic structure has smaller △ES1-T1 as compared to the linear structure. • The macrocyclic molecules have larger SOC and faster RISC rates, which also well explains the experimental predictions and results. • Compared to the linear structure, the macrocyclic structure has a smaller reorganization energy and H-R factor. Thermally Activated Delayed Fluorescent (TADF) molecules with Donor (D) -Acceptor (A) –Donor-Acceptor π-Conjugated Macrocycle structures have broad application potential in organic light-emitting diodes. In this paper, three D − A line type and one D − A − D − A π‑Conjugated Macrocycle molecules with same donor and acceptor groups are investigated using polarizable continuum model (PCM) combined with density functional theory (DFT) and time-dependent functional theory (TD-DFT) in solvent and film. It is found that the macrocyclic structure has a smaller energy gap (ΔE ST) between the first singlet excited state (S 1) and the first triplet excited state (T 1) than the linear structure. The TADF efficiency is also analyzed based on the calculation of spin–orbit coupling (SOC) and the (reverse) intersystem crossing (RISC) rates between S 1 and T 1. The macrocyclic molecules have larger SOC and faster RISC rates, which also well explains the experimental predictions and results. [ABSTRACT FROM AUTHOR]

In this work, we systematically study the photo physical properties for NIR-AIE-TADF molecules in toluene solvent, film and crystal by PCM and QM/MM method, respectively. First, the molecular luminescence was red-shifted by about 100 nm, when –CH3 in the molecule is replaced by –OCH3, which may be due to the increased vibrational intensity of the molecule, resulting in energy dissipation. Second, the vibrations were effectively suppressed in the solid state for both TBSMCN and O-TBSMCN molecules, which is the reason for the AIE of the molecules. Third, the molecules have a small △ES1-T1 in the solvent with TADF properties, and their △ES1-T1 is reduced and SOC is increased in the solid state, which is more favorable for the RISC. Fourth, by analyzing the nature of the transitions in the dimers in the film structure we find that O-TBSMCN molecule undergoes intermolecular charge transfer, which may be one of the reasons for its reduced film efficiency. [Display omitted] • The inhibition of vibration in the aggregated state is the main reason for AIE. • A smaller △E S1-T1 and a larger SOC in aggregate state, it is favorable for RISC. • The O-TBSMCN molecule undergoes intermolecular CT, which lower its film efficiency. TADF emitters with both high exciton utilization and luminescence efficiency show promising applications in OLEDs, especially it with AIE characteristics. However, theoretical studies on emitters with amorphous structure with the consideration of the solid-state effect are limited. In this work, a multi-scale simulation is performed to study the reported compounds TBSMCN and O-TBSMCN, which both possess distinct features of NIR-AIE-TADF. The packing modes of the molecules in film and crystal are obtained by molecular dynamics simulations (MD) and experiments, and then the photo physical properties are studied by using the QM/MM method. The results show that geometrical changes between the ground state (S 0) and the first singlet excited state (S 1) are restricted in aggregate state. Thus, the non-radiative energy consumption process is hindered, this indicates the AIE mechanisms. Second, the molecules exhibit a smaller △E S1-T1 and a more significant SOC in aggregate state, which is more favorable for the RISC. Finally, by analyzing the NTO of the dimers in the film, the O-TBSMCN molecule undergoes intermolecular charge transfer, which may be one of the reasons for the significant reduction in its film efficiency. Our calculations could help one to better understand the NIR-AIE-TADF mechanism from a theoretical perspective. [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]