Hot Electron Transfer Solar Cells Show Promise

Results of a study published in the Feb. 6 issue of Nature suggest the feasibility of photovoltaic cells based on a new device structure that captures energetic electrons generated by photon absorption in photoreceptive dyes and that transfers them through an ultrathin metal film into an inexpensive polycrystalline semiconductor. Although the initial devices, demonstrated by Eric W. McFarland and Jing Tang at the University of California, Santa Barbara, displayed an overall efficiency of less than 1 percent because of low dye coverage, their internal quantum efficiency of approximately 10 percent suggests that the approach holds promise with further development.

The solar cells comprise a layer of merbromin adsorbed onto an Au/TiO₂/Ti structure. The researchers suggest that the devices function by injecting photoexcited "hot" electrons through the Au and over the Schottky barrier at the Au/TiO₂ interface. Electrons then pass through an external circuit and return to the Au layer to replenish the electron content of the merbromin.

Other photoreceptors, such as semiconducting quantum dots, also may be employed as absorbers, McFarland noted.