Atomic layer deposited (ALD) ultrathin metal oxides, HfO2, Al2O3 and SiO2, were used to treat the surface of nanoporous TiO2 for dye sensitized solar cell (DSSC) application. X ray photoelectron spectroscopy was performed to probe the growth of metal oxides on TiO2 surface. ALD grown metal oxide layers on TiO2 surface did not block the porosity as observed in atomic force microscopic studies. Conformal surface coverage was achieved as shown by high resolution transmission electron microscopic analysis on ALD grown TiO2 and the thickness was about 2 nm. It was observed that performance of DSSC was significantly enhanced by ALD metal oxide surface treatment. The enhanced DSSC performance asserted that electron injection from the dye to TiO2 was not blocked while the electron trap from the conduction band of TiO2 to surface states was significantly suppressed and hence the improved performance. Further, it was noticed that the thickness of ALD metal oxide layers play a vital role in the photovoltaic performance of DSSCs.
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