A major advantage of solid-state dye-sensitized solar cells is that they do not suffer problems with solvent leakage and corrosion. Recent research into synthesis of the anode material, nanocrystalline TiO2, has opened up new insight into device optimization and control over properties. Steiner, Snaith and coworkers have developed a novel block-co-polymer directed synthesis of titania, and have correlated the conditions of synthesis to the resulting density of states. They studied hybrid cells comprising nanocomposites of titania and diblock co-polymers, and the structural influence on the electronic processes of charge generation, transport, separation and recombination. Their findings are important because they help understand the influence of the density of states on photovoltaic performance: an increase in the depth and width of the density of states corresponds to an increase in the photocurrent, but also a drop in the open-circuit voltage.
Using poly(isoprene-block-ethylene oxide) as a structure-directing agent allows the in situ formation of a carbon scaffold at high annealing temperatures in an inert atmosphere. As a result, titania crystallizes completely without loss of the mesostructure. The authors’ best polymer-TiO2 hybrid solar cell power conversion efficiency of 3.2% is already comparable with the 3.4% for a standard nanoparticle-based device, with room for further improvement. As this method is very different from the traditional colloidal assembly of TiO2 nanoparticles, it provides a new way of exploring and optimizing the anode properties of dye-sensitized solar cells as well as other kinds of devices.
Editor’s note: Kitty Cha is a guest blogger from Wiley’s MaterialsView blog.