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-offlight methods. For the typical thickness of organic light-emitting devices, the electron mobility of BPhen, 2.8 x 10(-4) cm(2)/V s, at 50 nm is smaller than the value 3.4 x 10(-4) cm(2)/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. (C) 2008 Elsevier Ltd. All rights reserved