Low-temperature ozone annealing for dye-sensitized solar cells

Abstract

The process whereby the TiO2 photoelectrode of dye-sensitized solar cells (DSSCs) is manufactured requires an annealing temperature of 450 °C. However, these DSSCs, which contain a low-cost, lightweight, and flexible plastic substrate, limit the annealing temperature to a maximum of 150 °C. This led us to develop a low-temperature (∼150 °C) annealing technique to process the TiO2 photoelectrode. The proposed method, which employs O3 as reactant, is based on the fact that O3 is thermally decomposed at ∼150 °C to produce atomic oxygen (O) atoms, to which the TiO2 photoelectrode is then exposed during annealing. Measurement of the carbon contents remaining on the TiO2 photoelectrode using energy dispersive X-ray spectrometry indicated that the O atoms can remove the organic binders contained in TiO2 paste. In addition, measurement of the energy conversion efficiency indicated that O atoms also have the ability to enhance TiO2 interparticle connections. This simple method to supply O atoms may not only be useful for treating the TiO2 photoelectrode of DSSCs but also for other surface treatments that require the use of O atoms.