Origin and significance of emitting dipole orientation (EDO) of emitters in organic light-emitting diodes (OLEDs) have been studied extensively in recent years. However, EDO of homoleptic Ir(III) complexes (Homo-IrCs) have received less attention due to their three-fold molecular symmetry and resulting expectation to have random EDO. Herein, we report the EDOs of Homo-IrCs doped in various host materials. Interestingly the EDO of Homo-IrCs varies from preferred horizontal direction to rather vertical direction depending on dopant and host molecules. The variation of EDO of Homo-IrCs is correlated with the direction of the transition dipole moment (TDM) against the molecular C₃ axis and the orientation of C₃ axis of the dopants in films. The average orientations of the Homo-IrCs are extracted from measured the horizontal dipole ratios (Θs) and calculated TDM directions. Angle between the TDM direction and C₃ axis in the Homo IrCs under investigation are larger than 54.7° corresponding to the mutually orthogonal axes among the three transition dipole vectors so that the EDO of Homo IrCs can deviate from random orientation depending on the orientation of the C₃ axis in films. Average molecular orientation of a HOMO IrC in films varies by 10°–13° depending on host materials. In contrast, smaller variation (<5°) is observed among different Homo IrCs in a same host. The results indicate that host material is one of the dominating factors determining orientation of Homo-IrC molecules. Tris[(3,5-difluoro-4-cyanophenyl)-pyridine]iridium(III) (FCNIr) shows exceptionally high horizontal orientation, which likely originates from the dipole-dipole interaction between the dopant and hosts. FCNIr doped in diphenyl[4-(triphenylsilyl)phenyl]phosphine oxide (TSPO1) shows strong preferred horizontal EDO with the Θ of 0.78, demonstrating the possibility of large Θ value of Homo-IrCs.

近年来，有机发光二极管（OLED）中的发射器的发射偶极子取向（EDO）的起源和意义得到了广泛的研究。然而，由于它们的三倍分子对称性和对具有随机EDO的期望，均纯Ir（III）配合物（Homo-IrCs）的EDO受到的关注较少。在此，我们报告了掺杂有多种基质材料的同型IrC的EDO。有趣的是，根据掺杂剂和主体分子的不同，Homo-IrCs的EDO从优选的水平方向变化到相当垂直的方向。Homo-IrCs的EDO的变化与跃迁偶极矩（TDM）相对于分子C ₃轴的方向以及C ₃的方向相关薄膜中掺杂剂的轴。从测量的水平偶极比（Θs）和计算的TDM方向中提取Homo-IrC的平均方向。在研究的同质IrC中，TDM方向与C ₃轴之间的角度大于54.7°，对应于三个跃迁偶极子矢量中相互正交的轴，因此，同质IrC的EDO可以根据其取向而偏离随机取向。 C ₃电影中的轴。薄膜中HOMO IrC的平均分子取向根据宿主材料的不同会在10°–13°之间变化。相反，在同一宿主中的不同Homo IrC之间观察到较小的变异（<5°）。结果表明主体材料是决定Homo-IrC分子取向的主要因素之一。三[[（3,5-二氟-4-氰基苯基）-吡啶]铱（III）（FCNIr）显示出极高的水平方向，这很可能源于掺杂剂与主体之间的偶极-偶极相互作用。掺杂在二苯基[4-（三苯基甲硅烷基）苯基]膦氧化物（TSPO1）中的FCNIr显示出较强的首选水平EDO，θ为0.78，这表明高IrCs的θ值的可能性。