We investigated the influence of ITO properties on the performance of bulk heterojunction solar cells. The morphology, electrical and optical properties of ITO electrodes were characterized. The power conversion efficiency of cells made on different ITO substrates varied significantly from 2.3% to 3.1%. It was found that for a higher sheet resistance ITO substrate, the sheet resistance was the dominant parameter affecting the performance of the based solar cells, while for the lower ( below 20 ohm/square) sheet resistance, transmittance in the region where polymer strongly absorbs and the surface roughness of the substrate had significant effect on the solar cells performance.
We performed a comprehensive study of the effect of transition metal oxide anode interlayer in bulk heterojunction solar cells based on P3HT:PCBM. We have investigated the influence of different metal oxides including tungsten oxide (WO<sub>3</sub>), vanadium oxide (V<sub>2</sub>O<sub>5</sub>) and molybdenum oxide (MoO<sub>3</sub>) on the solar cell performance. In addition, the influence of different deposition techniques (solution process and e-beam deposition/ thermal evaporation) has also been investigated. We found that deposition techniques play a significant role on the film quality and morphology and hence affect the photovoltaic performance. Obtained results are discussed in detail.