In this research, we report deep ultraviolet (DUV) light-assisted low-temperature crystallization of amorphous TiO2 films and their applications to solar energy conversion devices. Amorphous TiO2 films deposited by atomic-layer-deposition were photoactivated with DUV light under nitrogen atmosphere. Various film characterizations confirmed that DUV irradiation substantially accelerates the nucleation rate and reduces the minimum temperature for crystallization (anatase) of amorphous TiO2 film by 100 degrees compared with thermal annealing without DUV irradiation. Furthermore, it was demonstrated that the DUV photoactivation with concurrent thermal annealing induces the low-temperature formation of unconventional brookite phase and preferential facet orientation, which was never reported in the previous literature. Finally, the DUV-assisted low-temperature crystallization was successfully employed to form high-quality anatase films regardless of substrates, for high-performance photoelectrochemical cells on indium tin oxide and perovskite photovoltaics with very narrow performance variation. Our results suggest that DUV photoactivation can provide a low-temperature post-treatment for functional metal oxide thin films with well-defined crystallinity and preferred phase orientation on unconventional substrates.
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