Application of Sol-Gel Processed Titanium Oxide for Inverted Polymer Solar Cells as an Electron Transport Layer

The use of sol-gel processed titanium oxide (TiO2) as an electron transport layer in inverted bulk hetero-junction (BHJ) polymer solar cells (PSCs) was investigated. By adjusting the precursor/solvent ratio of the precursor sol, the thickness of the titanium oxide (TiO2) films was varied from 5 nm to 50 nm, and its effect on the photovoltaic performances was evaluated. The power conversion efficiency (PCE) of the devices was found to increase on decreasing the film thickness to 10 nm, and a slight decrease was observed below this critical thickness. We also investigated the effect of nitrogen-doping of TiO2 on the PCE of the cells. The inverted solar cells with N-doped TiO2 film gave 10% improved performance compared to the devices containing undoped TiO2 film.