Boron-Doped Diamond as an Efficient Back Contact to Thermally Grown TiO2 Photoelectrodes

Abstract

In the present work, we investigate the efficiency of TiO2 photoelectrode layers on boron-doped diamond foil (BDDF) in comparison with a classic conducting glass (fluorine-doped tin oxide, FTO) back contact. Crystalline thin TiO2 layers were prepared on the substrates by two different methods: (i) deposition of metallic Ti thin films followed by thermal oxidation to form TiO2 (TO-TiO2), (ii) reactive sputter deposition of TiO2 thin films and crystallization of these layers (SP-TiO2). The optimized layers show that TO-TiO2 films on BDDF deliver a significantly higher incident photon to current efficiency (IPCE) compared to directly sputtered SP-TiO2 layers and these layers on BDDF also outperform FTO as a back contact. We ascribe this beneficial effect of the BDDF back contact to the formation of an intermediate conductive phase of Ti carbides at the TO-TiO2/BDDF interface.