Effect of TiO2 interlayer on the performance of inverted polymeric solar cells

We report inverted bulk heterojunction organic solar cells (OSCs) by incorporating TiO2 as electron extracting layer. TiO2 was synthesized via sol-gel method. Solar cell's active layers (P3HT/PCBM blend) were deposited using low and high spin casting of 1000 rpm (20 s) and 2000 rpm (60 s) respectively. The film deposited with 1000 rpm was kept overnight to observe solvent soaking effect. The performance parameters of the devices were enhanced with inserting TiO2 interlayer. Solvent soaked OSCs have shown enhanced device performance parameters and exhibit higher power conversion efficiency of 3.32% in comparison to reference devices. Light soaking effect of solvent soaked OSCs was also observed. The power conversion efficiency is optimized by device irradiation which activates the device by filling the trap states present in the TiO2 interface and hence improving series resistance of the OSCs. TiO2 based organic solar cells (OSC) exhibits higher performance when compared to direct structure and ZnO based inverted devices. This suggests that interfacial electron transfer rates, charge carriers combination rates and photo reactivity changed efficiently due to insertion of TiO2 interlayer between transparent electrode and device's active layer.