Three triphenyl benzene derivatives of 1,3,5‐tri(m‐pyrid‐2‐yl‐phenyl)benzene (Tm2PyPB), 1,3,5‐tri(m‐pyrid‐3‐yl‐phenyl)benzene (Tm3PyPB) and 1,3,5‐tri(m‐pyrid‐4‐yl‐phenyl)benzene (Tm4PyPB), containing pyridine rings at the periphery, are developed as electron‐transport and hole/exciton‐blocking materials for iridium(III) bis(4,6‐(di‐fluorophenyl)pyridinato‐N,C^2′)picolinate (FIrpic)‐based blue phosphorescent organic light‐emitting devices. Their highest occupied molecular orbital and lowest unoccupied molecular orbital (LUMO) energy levels decrease as the nitrogen atom of the pyridine ring moves from position 2 to 3 and 4; this is supported by both experimental results and density functional theory calculations, and gives improved electron‐injection and hole‐blocking properties. They exhibit a high electron mobility of 10⁻⁴–10⁻³ cm² V⁻¹ s⁻¹ and a high triplet energy level of 2.75 eV. Confinement of FIrpic triplet excitons is strongly dependent on the nitrogen atom position of the pyridine ring. The second exponential decay component in the transient photoluminescence decays of Firpic‐doped films also decreases when the position of the nitrogen atom in the pyridine ring changes. Reduced driving voltages are obtained when the nitrogen atom position changes because of improved electron injection as a result of the reduced LUMO level, but a better carrier balance is achieved for the Tm3PyPB‐based device. An external quantum efficiency (EQE) over 93% of maximum EQE was achieved for the Tm4PyPB‐based device at an illumination‐relevant luminance of 1000 cd m⁻², indicating reduced efficiency roll‐off due to better confinement of FIrpic triplet excitons by Tm4PyPB in contrast to Tm2PyPB and Tm3PyPB.

中文翻译：

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用于高效蓝磷光OLED的含吡啶的三苯苯电子传输材料的结构-性能关系

1,3,5-三三个三苯基苯衍生物（米-吡啶-2-基-苯基）苯（Tm2PyPB），1,3,5-三（米-吡啶-3-基-苯基）苯（Tm3PyPB）和1,3,5-三（米-吡啶-4-基-苯基）苯（Tm4PyPB），含吡啶环在外围，被开发用作电子传输和空穴/激子阻挡材料铱（III）双（4,6-（二氟苯基）吡啶基-N，C ^2'）基于吡啶甲酸（FIrpic）的蓝色磷光有机发光器件。当吡啶环的氮原子从位置2移至3和4时，它们的最高占据分子轨道和最低未占据分子轨道（LUMO）的能级降低；实验结果和密度泛函理论计算都支持这一点，并提供了改进的电子注入和空穴阻挡性能。它们具有10 ^-4 –10 ^-3  cm ²  V ^-1  s ^-1的高电子迁移率并具有2.75 eV的高三重态能级。FIrpic三重态激子的约束在很大程度上取决于吡啶环的氮原子位置。当吡啶环中氮原子的位置发生变化时，掺有菲尔比斯的薄膜的瞬态光致发光衰减中的第二个指数衰减分量也会减小。由于降低的LUMO能级而改善了电子注入，从而使氮原子位置发生变化时，驱动电压也降低了，但是基于Tm3PyPB的器件实现了更好的载流子平衡。基于Tm4PyPB的设备在与照明相关的亮度为1000 cd m ^-2时，实现了超过最大EQE的93％的外部量子效率（EQE），表明与Tm2PyPB和Tm3PyPB相比，Tm4PyPB更好地限制了FIrpic三重态激子，从而降低了效率下降。