Structural and optical characterization of electrodeposited CdSe in mesoporous anatase TiO2 for regenerative quantum-dot-sensitized solar cells
We investigated CdSe-sensitized TiO2 solar cells by means of electrodeposition under galvanostatic control. The electrodeposition of CdSe within the mesoporous film of TiO2 gives rise to a uniform, thickness controlled, conformal layer of nanostructured CdSe particles intimately wrapping the anatase TiO2 nanoparticles. This technique has the advantage of providing not only a fast method for sensitization (<5 min) but also being easily scalable to the sensitization of large-area panels. XRD together with SAED analysis highlight that the deposit of CdSe is exclusively constituted of the hexagonal polymorph. In addition, hierarchical growth has also been shown, starting from the formation of a TiO2-CdSe core-shell structure followed by the growth of an assembly of CdSe nanoparticles resembling cauliflowers. This assembly exhibits at its core a mosaic texture with crystallites of about 3 nm in size, in contrast to a shell composed of well-crystallized single crystals between 5 and 10 nm in size. Preliminary results on the photovoltaic performance of such a nanostructured composite of TiO2 and CdSe show 0.8% power conversion efficiency under A.M. 1.5 G conditions-100 mW cm(-2) in association with a new regenerative redox couple based on cobalt(+III/+II) polypyridil complex (V-oc = 485 mV, J(sc) = 4.26 mA cm(-2), ff = 0.37).