Visible light sensitisation of titanium dioxide using a phenylene vinylene polymer

The photophysical properties of thin films of poly[2-methoxy-5-(2′-ethyl-hexyloxy), para-phenylene vinylene] (MEH-PPV) on TiO2 substrates have been investigated. Evidence for dissociation of excitons at the MEH-PPV/TiO2 interface and electron injection into the conduction band of TiO2 has been found from current/voltage characteristics. The open circuit voltage is to 0.92 V for these cells and an energy conversion efficiency of 0.15% is found for white light. Capacitance measurements follow the Mott–Schottky relationship and reveal an acceptor density of NA≈9×1017 cm−3 for the polymer layers. From analysis of the luminescence as a function of the film thickness, an exciton diffusion length of 20±3 nm for MEH-PPV is derived.