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<p>Herein, a molecular design strategy leveraging antiaromatic azepino[3,2,1-<i>kl</i>]phenothiazine (APT) to amplify electron delocalization in multiple resonance thermally activated delayed fluorescence (MR-TADF) materials is proposed. Two distinct cyclization approaches integrate the APT unit into the parent scaffold BBCz-SB, extending <i>π</i>-conjugation and producing a series of narrowband pure green MR-TADF emitters. Further benzene ring functionalization markedly promotes intramolecular orbital delocalization, culminating in ultrapure green electroluminescence with outstanding efficiency. These emitters show bright photoluminescence at 506–518 nm with full-widths at half maximum (FWHM) of around 26 nm, achieving an optimal Commission Internationale de L’Eclairage (CIE) coordinate of (0.17, 0.74) in toluene, and exhibit high reverse intersystem crossing rates exceeding 10<sup>5</sup> s<sup>−1</sup>. Bottom-emission organic light-emitting diodes (OLEDs) based on these emitters exhibit excellent performance. In particular, the APT-BN2-based device achieves the maximum external quantum efficiency (EQE<sub>max</sub>) of 38.3% in a single host configuration. In a binary exciplex host to suppress efficiency roll-offs, the APT-Ph-BN-based device achieves an EQE<sub>max</sub> of 36.8%, with an emission peak at 523 nm, FWHM of 36 nm and CIE coordinates of (0.23, 0.70). Remarkably, the corresponding top-emission OLED delivers an EQE<sub>max</sub> of 52.3% along with FWHM of 17.6 nm and CIE coordinates of (0.128, 0.791).</p>

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Antiaromatic azepino[3,2,1-kl]phenothiazine promoted electron delocalization in multiple resonance emitters for highly efficient narrowband emission

  • 期刊论文

  • 发表日期：

    2026年1月12日

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  • Jun-Tao Hu,
  • Yitong Zeng,
  • Zhizhi Li,
  • Guo-Xi Yang,
  • Mengke Li,
  • Zhihai Yang,
  • Yu Fu,
  • Xiangyi Cheng,
  • Yongxia Ren,
  • Shaofeng Chen,
  • Kunkun Liu,
  • Shi-Jian Su

摘要

Herein, a molecular design strategy leveraging antiaromatic azepino[3,2,1-kl]phenothiazine (APT) to amplify electron delocalization in multiple resonance thermally activated delayed fluorescence (MR-TADF) materials is proposed. Two distinct cyclization approaches integrate the APT unit into the parent scaffold BBCz-SB, extending π-conjugation and producing a series of narrowband pure green MR-TADF emitters. Further benzene ring functionalization markedly promotes intramolecular orbital delocalization, culminating in ultrapure green electroluminescence with outstanding efficiency. These emitters show bright photoluminescence at 506–518 nm with full-widths at half maximum (FWHM) of around 26 nm, achieving an optimal Commission Internationale de L’Eclairage (CIE) coordinate of (0.17, 0.74) in toluene, and exhibit high reverse intersystem crossing rates exceeding 105 s−1. Bottom-emission organic light-emitting diodes (OLEDs) based on these emitters exhibit excellent performance. In particular, the APT-BN2-based device achieves the maximum external quantum efficiency (EQEmax) of 38.3% in a single host configuration. In a binary exciplex host to suppress efficiency roll-offs, the APT-Ph-BN-based device achieves an EQEmax of 36.8%, with an emission peak at 523 nm, FWHM of 36 nm and CIE coordinates of (0.23, 0.70). Remarkably, the corresponding top-emission OLED delivers an EQEmax of 52.3% along with FWHM of 17.6 nm and CIE coordinates of (0.128, 0.791).