Using an aerosol technique, in which ultrasonically formed droplets of titanium tetraisopropoxide are pyrolysed, thin films of nanosized particles of anatase TiO2 can be deposited. The size of the particles and the film morphology are strongly dependent on deposition parameters like reaction temperature, concentration of the precursor, and gas flow. At best, films can be formed consisting of homogeneous, stoichiometric anatase TiO2 particles with a size of about 50 nanometer. With these films, solar cells have been constructed by spin casting poly(3-octyl)thiophene (P3OT) on top. Cell characteristics of the devices with a 1 μm film of TiO2 and an equivalence of 30 nm of PT inside the pores are Isc: 0.25 mA/cm2, Voc: 0.72 V, FF: 0.35 and η: 0.06% using white light with an intensity of 1000 W/m2 (not AM 1.5). The IPCE is 2.5% at 488 nm.
Solar cells composed of thin layers of titanium dioxide (TiO2) and zinc phthalocyanine (ZnPc) show a large decay of the photocurrent in ambient atmosphere. This decay is caused by the combined presence of oxygen, light, and an external electric field. A two-step mechanism is proposed which involves the formation of a mobile photodopant arising from the present of molecular oxygen in the layers. In the first step, oxygen radical anions are formed under influence of bandgap illumination of ZnPc. Subsequently these negative charged species drift towards the interface with TiO2 under the influence of an external electric field. They accumulate and quench (pi) (pi) *-singlet excitons which depresses the photocurrent dramatically. A concentration of more than 5.1018 cm-3 ionized oxygen species is found to be present in the ZnPc films under ambient atmosphere and 5-mW 670-nm irradiation, which is two orders of magnitude higher than in the dark.