The estimation of electron mobility of 4,7-diphyenyl-1, 10-phenanthroline using space-charge-limited currents

The electron mobility of 4,7-diphyenyl-1, 10-phenanthroline (BPhen) at various thicknesses (50–300 nm) has been estimated by using space-charge-limited current measurements. The mobility at bulk property dominant thickness is in excellent agreement with the results from time-of-flight methods. For the typical thickness of organic light-emitting devices, the electron mobility of BPhen, 2.8×10−4 cm2/V s, at 50 nm is smaller than the value 3.4×10−4 cm2/V s at 300 nm (electric field at 0.3 MV/cm). The authors suggest that the lower mobility is caused by the interfacial trap states.