High photostability and quantum yield of nanoporous TiO2 thin film electrodes co-sensitized with capped sulfides

Photoelectrochemical electrodes have been prepared by sequential deposition of quantum sized PbS, CdS and ZnS particles on TiO2 nanocrystalline films. Their photoelectrochemical properties have been studied in a two-electrode system which conforms more closely to practical conditions. The results show that the ternary sulfide PbS/CdS/ZnS co-sensitized TiO2 electrode generates incident photon-to-current conversion efficiency (IPCE) as high as nearly 100% under irradiation with 400 nm light; moreover its photostability is strongly improved, and this is the first report of this so far. The highest photoelectrical conversion efficiency is obtained for the TiO2/PbS/CdS/ZnS electrode, and is about twice as much as that of TiO2/PbS.