Phosphorus-oxygen modified anthracene-based emitters for high-efficiency deep-blue OLEDs approaching the BT.2020 blue standard

The development efficient deep-blue fluorescent materials present a significant challenge in the field of organic optoelectronics. The hot exciton mechanism, which facilitates the transition of excitons from high-energy excited triplet states (T_n, n ≥ 2) to singlet states (S_m, m ≥ 1) via reverse intersystem crossing (hRISC) pathways, has emerged as an effective strategy for designing efficient organic light-emitting diodes (OLEDs). In this study, we modified anthracene with non-conjugated triphenylphosphine oxide (PO) and tetraphenylsilane (TPS) groups to construct two positional isomers, p-TPSAnPO and m-TPSAnPO. Photophysical studies indicate that the weak electron-withdrawing and electron-donating of the PO and TPS groups endow p-TPSAnPO and m-TPSAnPO with local excited (LE) characteristics in their lowest singlet state (S₁), resulting in highly efficient deep-blue emission. Doped devices based on p-TPSAnPO and m-TPSAnPO achieved maximum external quantum efficiencies (EQE_max) of 10.07 % and 10.77 %, respectively, with Commission Internationale de l ́Eclairage (CIE) coordinates of (0.155, 0.043) and (0.152, 0.048), approaching BT.2020 blue standard. The theoretical calculations further reveal that the S₁, T₂, and T₃ states of these materials are localized on the anthracene moiety, while the higher-energy S₂ and T₄ states are induced by the electron-withdrawing PO group, forming charge transfer (CT) and hybridized local and charge transfer (HLCT) states. The transitions between these high-energy states create multiple hRISC pathways. Additionally, sensitization experiments on high-energy triplet states confirm that these materials indeed exhibit effective hRISC processes, enabling them to achieve high efficiency in electroluminescent applications. This work provides important theoretical and experimental guidance for designing efficient anthracene-based hot exciton deep-blue materials.