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We characterize the electron transport properties of 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) thin films with various thicknesses (150–260 nm) via admittance spectroscopy (AS). The electron mobilities of TPBi films with different thicknesses are calculated in the range from (5.6 × 10–8) to (2.1 × 10–5) cm2 V–1 s–1, which increase as the applied electric field increases. It is found that the electron mobility of the TPBi thin films is much lower than those of 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB) and 1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPB). We also investigate the performances of red organic light-emitting diodes (OLEDs) based on TPBi, TmPyPB, and BmPyPB as the corresponding electron transport layers (ETLs). The results show that the performance of the TPBi ETL device is obviously inferior to those of the other two devices. By the analysis of the energy-level diagram of the used materials and work mechanisms of the devices, the reasons for their performance differences are examined.
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