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.