Inverted organic solar cells employing RGO/TiO_x composite films as electron transport layers

Reduced graphene oxide (RGO)/titanium oxide (TiO_x) (RGO/TiO_x) composite films are successfully prepared by a sol-gel method. Inverted organic solar cells incorporating RGO/TiO_x composite as electron transport layer and MoO₃ as hole transport layer were fabricated. A short-circuit current of 9.85 mA/cm² and power conversion efficiency of 3.82% are achieved by using the RGO/TiO_x composite films with 0.083 mg/mL of RGO in TiO₂ colloidal solution as electron transport layers for the inverted solar cells based on P3HT and PCBM, which are increased by 14.8% and 26.1% compared with the reference device without RGO, respectively. Impedance measurements revealed that the significantly enhanced efficiency was attributed to the RGO/TiO_x composite films with efficient electron transport