Fig.1 Molecular design of BN-I2S. (a) The molecular design strategy of BN-IP and BN-I2S. (b) Frontier molecular orbital distributions and calculated excited-state energy levels of BN-IP and BN-I2S. (c) Reorganization energy and (d) Huang-Rhys factors of BN-IP and BN-I2S.#

Fig.2 Crystal packing and photophysical properties of the emitters. (a) Crystal packing diagrams along the a (a), b (b), c (c) axes (The BN-embedded polycyclic frameworks are colored green, and the peripheral BTPSP groups are shown in magenta). (d) Top and side views of the dimer. (e) The UV–vis spectra and fluorescence spectra of BN-IP and BN-I2S in diluted toluene (1.0 × 10−5 M) (Insets show photographs of the toluene solution upon irradiation of 365 nm ultraviolet light). (f) The fluorescence spectra of BN-IP and BN-I2S in 3 wt.% DMIC-TRZ doped films (Insets show the corresponding film photographs under 365 nm UV light irradiation). (g) Transient PL decay curves of BN-IP and BN-I2S in 3 wt.% DMIC-TRZ doped films.#

在光物理性质测试中，如图2所示，BN-I2S在甲苯稀溶液中展现出521 nm的发射峰，半峰全宽仅为21 nm。在3 wt%浓度的掺杂薄膜中，BN-I2S保持了高达99%的荧光量子产率。更重要的是，变角度偏振光光致发光光谱测量结果表明，BN-I2S在薄膜中的水平过渡偶极取向比例（Θ//）高达95%，远高于对照分子BN-IP的86%。这种高度趋向于平行于衬底的偶极取向能够大幅减少光在器件内部的波导损耗，从而显著提升光出射效率。

Fig.3 Performance for binary device. (a) Device structure. (b) EL spectra (recorded at a luminance of 1000 cd m−2). (c) EQE-L curves. (d) The CE-L and PE-L curves. (e) J-V-L curves. (f) CIE coordinates of BN-IP-based and BN-I2S-based devices at luminance of 1000 cd m−2, inset: device photographs.#

在电致发光器件性能方面，研究团队构建了二元及三元敏化OLED器件，如图3和图4所示。在二元器件中，BN-I2S展现出527 nm的窄带绿光发射，半峰全宽为27 nm，最大外部量子效率达到了28.2%。为了进一步释放材料的潜能并延长器件寿命，研究人员在发光层中加入磷光客体Ir(ppy)₃构建三元敏化器件。如图4所示，高效的能量转移使得敏化器件的最大外部量子效率进一步提升至31.8%，最大功率效率达到150.1 lm/W。

Fig.4 Performance for phosphor-sensitized device. (a) EL spectra (recorded at a luminance of 1000 cd m−2). (b) The EQE-L curve. (c) J-V-L curves. (d) Luminance-deterioration curve at the initial luminance (_L_0) of 5000 cd m−2 (LT(1000 cd m−2) = LT(L0) × [L0 / (1000 cd m−2)]n, with an empirical acceleration factor of n = 1.75).#

器件运行稳定性的测试结果令人瞩目，如图4所示。在初始亮度为5000 cd/m²的加速老化测试中，基于BN-I2S的三元敏化器件表现出显著优于对照器件的耐久性，其LT80寿命达到723小时。根据经验公式推算至1000 cd/m²的常用初始亮度下，BN-I2S器件的LT80寿命达到了12087小时，约为对比分子BN-IP器件的2.2倍。这表明大体积多硅基团不仅能够优化分子取向，还能在器件运行过程中有效减弱分子的相互作用，抑制有害的德克斯特能量转移，从而大幅降低电应力并延长器件寿命。