<title>Concept of dye-sensitized mesoporous solid state heterojunction solar cells</title>

Solar cells based on dye-sensitized mesoporous films of TiO<SUB>2</SUB> are low cost alternatives to inorganic semiconductor devices. Solar energy conversion efficiencies of up to 10% have been achieved with such films when used in conjunction with liquid electrolytes. Practical advantage may be gained by the replacement of the liquid electrolyte with a solid charge transport material and various concepts have been proposed in literature to realize such solid-state dye-sensitized heterojunctions. Recently high incident photon to electric current conversion efficiencies have been achieved with a cell consisting of a dye-derivatized mesoporous TiO<SUB>2</SUB> film contacted by a new organic hole conductor. Photoinduced charge carrier generation shows to be very efficient in such devices, while interfacial charge recombination during charge collection can be revealed as the major loss mechanism. Surface treatments with pyridine derivatives proved to significantly improve the energy conversion efficiency of the device.