We report the electrical properties of inverted P3HT:PC71BM bulk hetero-junction (IBHJ) with Cs2CO3 and MoO3 interlayers. The current density (J)-voltage (V) characteristics of the inverted P3HT:PC71BM bulk hetero-junction solar cells are studied, where MoO3 thickness is varied from 0.5 to 2 nm. The temperature independent, symmetric J-V characteristics in dark were found in the low bias voltage region between -0.35 and 0.35 V, and they exhibited the power law relationship J-V-1,V-2 when the MoO3 thickness is between 1 and 2 nm. Open-circuit voltages at various light intensities of the IBIAJ cell plotted as a function of absolute temperature converge to similar to 0.965 Vat zero temperature, which is very close to the energy difference between LUMO of PC71BM and HOMO of P3HT. (C) 2011 Elsevier B.V. All rights reserved.