As society faces the problems derived from global warming and excessive pollution, harvesting solar energy and storing it into chemical bonds is one of the most promising paths in the so called solar fuels economy. Between them, photoelectrochemical water splitting offers the possibility to directly convert water and solar energy into hydrogen and oxygen with competitive efficiencies.
To enable silicon to be used as photocathode for hydrogen evolution, protective and conductive coatings are needed stable from acidic to basic electrolytes while transparent to light and with proper band alignment to be deposited on silicon. One of the best candidates is Titanium Dioxide, as it is known to be stable in wide range of pH. In this context, Atomic Layer Deposition has attracted much attention during the last decade for depositing thin protective films as it offers the possibility to cover the photoabsorbing material with conformal and pinhole-free thin layers, although few studies have used TiO2 for photocathodic hydrogen evolution. Better understanding on the requirements of ALD grown TiO2 properties to be used as cathodic transparent, protective and conductive layer is needed.
In the present study, TiO2 layers have been grown by ALD on n+p and n+-Silicon substrates. To understand the role of the crystallographic structure on the charge transfer across these layers for photoelectrochemical devices, the growth temperature has been modified. A model is presented to explain the charge transfer mechanism across the ALD grown TiO2 layer upon modifications in the growth temperature.
 S. M. Bhola and B. Mishra, “Effect of ph on the electrochemical properties of oxides formed over β - Ti-15Mo and mixed Ti-6Al-4v alloys,” Int. J. Electrochem. Sci., vol. 8, no. 5, pp. 7075–7087, 2013.