Abstract Bipolar host materials with balanced charge transporting property were synthesized using a solvent-less green reaction method. The characteristics of these synthesized bipolar host materials were examined by thermal and spectroscopic analysis. The energy levels of these materials were estimated from cyclic voltammograms and absorption spectra. The optimized molecular geometries and spatial distributions were obtained from molecular simulations. Moreover, the current density vs. voltage features of single-carrier devices were investigated to assess the bipolar transport characteristics of the host materials. As the length of the alkyl chain increased, the electron-transporting capability and hole-transporting ability exhibited optimum values at the octyl chain attachment. The current efficiency, power efficiency and quantum efficiency values of white organic light-emitting diodes prepared by blending blue and yellow iridium phosphors with these bipolar hosts were high with decreasing alkyl chain length. The result was remarkably similar to the trend of current density characteristics of single-carrier devices. The power efficiency of the octyl chain attached bipolar host was approximately three times higher than that of typical blended hole and electron transporting materials. This enhanced efficiency was attributed to the well-balanced charge transfer by the bipolar host material inside an emissive layer. Moreover, the morphology of the device fabricated with a blend of charge transport materials changed due to deterioration, whereas that of the device fabricated with bipolar host materials did not change after 12 h of operation at 9 V.

中文翻译：

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平衡双极主体材料中的电荷传输特性

摘要 采用无溶剂绿色反应法合成了具有平衡电荷传输性能的双极性主体材料。这些合成的双极主体材料的特性通过热分析和光谱分析进行了检查。这些材料的能级是根据循环伏安图和吸收光谱估计的。优化的分子几何形状和空间分布是从分子模拟中获得的。此外，研究了单载流子器件的电流密度与电压特性，以评估主体材料的双极传输特性。随着烷基链长度的增加，电子传输能力和空穴传输能力在辛基链连接处表现出最佳值。目前的效率，通过将蓝色和黄色铱磷光体与这些双极主体混合制备的白色有机发光二极管的功率效率和量子效率值随着烷基链长度的降低而提高。结果与单载流子器件的电流密度特性趋势非常相似。辛基链连接的双极主体的功率效率比典型的混合空穴和电子传输材料的功率效率高约三倍。这种提高的效率归因于发射层内双极主体材料的良好平衡的电荷转移。此外，用电荷传输材料的混合物制造的器件的形态由于劣化而发生变化，而用双极主体材料制造的器件的形态在 9 V 下运行 12 小时后没有变化。