Enhanced hydrogen gas generation rate by n-GaN photoelectrode with immersed finger-type indium tin oxide ohmic contacts

Abstract

To enhance the efficiency of photogenerated electron collection in the n-type working electrode, Indium Tin oxide (ITO) finger-type ohmic contacts were immersed in NaCl electrolyte because ITO is a well-known transparent and conductive optical film and the ITO/n-GaN contact exhibited ohmic property when the carrier concentration of n-GaN were close to 1×10 19 /cm 3 . We found that the performances of the n-GaN photoelectrochemical cells with finger-type ITO ohmic contacts in photocurrent densities and hydrogen gas generation rates were both better than the n-GaN without finger-type ITO ohmic contacts. Related analyses have been performed and will be presented in this paper to explain the possible mechanism from the point of view of electrochemical analysis. Besides, after the photoelectrochemical measurements we observed that the adhesion of ITO/n-GaN contacts was pretty good. Finally, we did the surface analysis by scanning electron microscope (SEM) before and after the photoelectrochemical measurements to conform the surface morphology of ITO almost did not change in the NaCl electrolyte. This indicates that ITO is a good candidate material for the immersed ohmic contact in water splitting system.