Contactless determination of the efficiency of interfacial charge separation in a TiO2/phenylene vinylene polymer junction

We have used the flash-photolysis time-resolved microwave conductivity technique (TRMC) to monitor charge separation between a smooth film of anatase TiO₂ (ca 80 nm) and spin-coated layers of a dialkoxyphenylene-vinylene polymer (20–140 nm thick) on nanosecond flash-photolysis in the polymer absorption band at 544 nm. The quantum efficiency of electron injection into the TiO₂ from photons absorbed in the polymer layer can be calculated by comparing the conductivity resulting from 544 nm irradiation with that from direct band gap excitation of the anatase layer at 308 nm. The maximum efficiency per incident photon, is ca 6% for thicknesses in the range of 30–50 nm of the polymer layer. Charge separation persists well into the microsecond region.