Enhanced Photovoltaic properties of P3HT/Cr–TiO2 bilayer film heterojunction solar cells

• The Cr–TiO2 nanocrystal films were prepared by sol–gel method.
• Band gap of the TiO2 was successfully narrowed by Cr3+ doping.
• The Cr–TiO2 was successfully used to assemble P3HT/Cr–TiO2 bilayer solar cells.
• The Voc was enhanced from 0.42 V to 0.99 V with increase of Cr3+ concentration.
• The optimal η is improved over 9 times than that of the cell based on pure TiO2.

The simple bilayer solar cells, composed of poly (3-hexylthiophene-2,5-diyl) (P3HT) and chromium doped titanium dioxide (Cr–TiO2) nanocrystal films, were fabricated by sol–gel method. The performances of structurally identical polymer–inorganic heterojunction solar cells Cu/Cr–TiO2/P3HT/FTO/Glass with various Cr3+ doping concentration were systematically investigated and compared. The results indicate that the samples’ open-circuit voltage is remarkably enhanced from 0.42 V to 0.99 V, and short-circuit photocurrent increases at first and then reduces, with the increase of Cr3+ doping concentration. The enhancement mechanism of photovoltaic properties is discussed in detail.