Fe doped TiO2 thin film as electron selective layer for inverted solar cells

• Fe doped and undoped TiO2 thin films fabricated by sol–gel method.
• Inverted type solar cells were fabricated with Fe doped TiO2 thin films.
• A dramatic increase was observed in the JSC with the 1% Fe doped TiO2 solar cells.
• Isc and Voc showed maximum values at 1% Fe2+ concentration.
• Solar cell efficiency of 2.78% was obtained at 1% Fe2+ concentration.

Inverted P3HT:PCBM based organic solar cells were fabricated by using Fe2+ doped TiO2 films as electron selective layer. Pure and Fe2+ doped TiO2 films were prepared by sol–gel method and the optical as well as the structural properties of the thin films were characterized by UV–Vis spectrophotometer and SEM. The concentration of Fe2+ was varied as 0.5%, 1%, 2% and 3% (w/w) in TiO2 layer and the influence of Fe2+ doping on the solar cell parameters were systemically investigated. Photocurrent density of the solar cells as increased from 8.75 to 13.8 mA/cm2, whereas the solar cell efficiency changed from 1.7% to 2.79% by using Fe2+ doped TiO2 electron selective layer. It was experimentally found and demonstrated that charge injection and selection in the TiO2 interlayer was improved by doping of Fe2+ atoms in the TiO2.