P3HT:PCBM polymer solar cells with TiO2 nanotube aggregates in the active layer

P3HT:PCBM polymer solar cells with a very small amount of TiO2 nanotube aggregates (0.002 mol per 100 mL) in the active layer have been fabricated. Although in dye-sensitized solar cells nanotube aggregates have been shown to increase light absorption of devices, it was found that TiO2 nanotube aggregates reduced the absorbance of the active layer in our case. However, its positive role on the charge collection and transportation maintained the EQE the same as a conventional P3HT: PCBM device and improved the electron mobility from 5.71 x 10(-5) cm(2) V-1 s(-1) to 7.22 x 10(-5) cm(2) V-1 s(-1). The final devices showed a 15% increase in power conversion efficiency compared to conventional P3HT:PCBM devices. The effects of TiO2 nanotube aggregates on the morphology of the active layer were studied by AFM.