Four new blue light-emitting materials based on benzo[1,2-d:4,5-d′]bisoxazole (BBO) have been synthesized, characterized, and fabricated into organic light-emitting diode (OLED) devices. Using a combination of theoretical and experimental methods, we investigated the effect of conjugation by comparing bulky alkyl groups and planar aromatic groups along the 2,6-axis. Two of these molecules, PB2Cz and PB3Cz, are cross-conjugated cruciform-type BBOs with phenyl and carbazole groups along the 2,6 and 4,8 axes, respectively. The other two molecules, AB2Cz and AB3Cz, have extended conjugation via the carbazole groups along the 4,8-axis and bulky adamantyl groups along the 2,6-axis. Concurrently, we explored the effect of regioisomerism on optoelectronic and device properties arising from attaching carbazole at the 2- (2Cz) or 3- (3Cz) position along the 4,8-axis. The materials’ geometric and electronic properties were predicted using time-dependent density functional theory (TD-DFT) calculations at the mPW3PBE/SV level. The molecules’ photoluminescent properties were measured in solution and film states. The BBO molecules were used as dopants in mixed host/guest OLED devices, producing teal to deep blue emission. Specifically, the AB2Cz and AB3Cz, with adamantyl on the 2,6-axis, exhibit blue to deep-blue emissions of 414–422 nm (CIE_x < 0.20, CIE_y < 0.10). In comparison, PB2Cz and PB3Cz have slightly longer emission wavelengths of 472–476 nm (CIE_x < 0.16, CIE_y < 0.28) and high brightness of 2700–3500 cdm^–2. The BBOs with 2Cz resulted in more efficient devices with EQEs of ∼2.8–3.2%, while the 3Cz BBOs had EQEs of ∼1.1–1.5%. This work provides insight into designing efficient, purely organic blue-fluorescent OLED materials based on the BBO moiety.

中文翻译：

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评估扩展共轭和区域异构对蓝光发射苯并二恶唑的光电性质和器件效率的影响


四种基于苯并[1,2-d:4,5-d']双恶唑（BBO）的新型蓝光材料已被合成、表征并制造成有机发光二极管（OLED）器件。我们结合理论和实验方法，通过比较沿 2,6 轴的大烷基和平面芳香基团，研究了共轭的影响。其中两个分子 PB2Cz 和 PB3Cz 是交叉共轭的十字形 BBO，分别沿 2,6 和 4,8 轴带有苯基和咔唑基团。另外两个分子 AB2Cz 和 AB3Cz 通过沿 4,8 轴的咔唑基团和沿 2,6 轴的大金刚基团延伸共轭。同时，我们探讨了在沿 4,8 轴的 2- (2Cz) 或 3- (3Cz) 位置连接咔唑所产生的区域异构现象对光电和器件性能的影响。使用 mPW3PBE/SV 级别的时间相关密度泛函理论 (TD-DFT) 计算来预测材料的几何和电子特性。在溶液和薄膜状态下测量了分子的光致发光特性。 BBO 分子在混合主/客体 OLED 器件中用作掺杂剂，产生青色至深蓝色的发射光。具体而言，AB2Cz 和 AB3Cz（2,6 轴上有金刚烷基）表现出 414–422 nm 的蓝色至深蓝色发射（CIE _x < 0.20，CIE _y < 0.10）。相比之下，PB2Cz 和 PB3Cz 的发射波长稍长，为 472–476 nm（CIE _x < 0.16，CIE _y < 0.28），亮度较高，为 2700–3500 cdm ^–2 。具有 2Cz 的 BBO 产生了更高效的器件，EQE 为 ∼2.8–3.2%，而 3Cz BBO 的 EQE 为 ∼1.1–1.5%。 这项工作为设计基于 BBO 部分的高效、纯有机蓝色荧光 OLED 材料提供了见解。