Is it possible to efficiently harness the often dim and indirect light found inside a room (e.g., from incandescent bulbs, fluorescent tubes, compact fluorescent bulbs, and light emitting diodes). The answer would now appear to be "yes."
A Walsh firm claims to have taken the efficiency of dye-based cells from 15% to 26%, which if correct would allow its economically efficient deployment indoors. Dye-based cells were invented at the Federal Polytechnic School of Lausanne, Switzerland, in the 1990's. Tinker with the composition of the dye, and the frequency of light that can be captured can be adjusted to make dye-based cells more flexible than silicon cells.
The dye molecules are bound to titanium dioxide, a less expensive semiconductor than silicon. The assembly is immersed in an electrolyte and sandwiched between two electrodes. When a photon of light is absorbed by a dye molecule, an electron is knocked into the titanium dioxide. Thereafter the electron travels to one of the two electrodes and a current is generated. Another advantage of dye-based cells is that they are literally flexible; some are already being woven into clothing to power cell phones, IPods etc.
Another potential market is to provide photovoltaics in regions in which silicon cells are not that well suited, such as areas frequently overcast or foggy.
Further information on dye-based cells can be found at: http://www.g24i.com/news,dye-sensitized-solar-to-go,179.html; http://www.g24i.com/news,dye-sensitized-cells-break-new-record,215.html; http://www.theengineer.co.uk/sectors/energy-and-environment/news/dye-based-organic-pvs-could-remove-need-for-batteries/1012299.article; http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell; and, http://www.greenmanufacturer.net/news/power-sources/2012/04/12/new-record-set-for-recycling-indoor-light-to-electricity.