Charge transport characteristics in P3HT:PCBM organic blends under illumination: Influence of metal work functions

The authors investigate the effects of metal work functions on charge transport characteristics in P3HT:PCBM bulk heterojunction under illumination by evaluating the temperature dependence of current-voltage characteristics. Schottky thermal emission current plays a dominant role on charge transport in the devices with Au or Al alloys used as electrodes. Whereas, a combined bulk limited conduction mechanism corresponding to three-dimensional variable-range hopping model and space charge limited current (SCLC) with an exponential distribution of traps (filled and unfilled) occurs in the device with Al used as electrode. And a shift to LUMO state of PCBM for trap density distribution is observed due to temperature dependence of Fermi level in PCBM material. Crown Copyright (C) 2012 Published by Elsevier B. V. All rights reserved.