A small org. sensitizer, the polyene-diphenylaniline dye D5, was compared with the std. sensitizer N719 [Ru(dcbpy)2(NCS)2] in a dye-sensitized solar cell investigation. In solar cells with relatively thin layers of mesoporous TiO2 (<3 μm) D5 outperformed N719 because of its high extinction coeff. D5 showed also better performance than N719 in the case of sensitization of mesoporous ZnO. In solid-state solar cells, where the iodide/triiodide electrolyte was replaced by an amorphous hole conductor (spiro-OMeTAD), D5 gave promising preliminary results. The hole cond., obsd. in monolayers of D5 adsorbed at TiO2, may possibly lead to improved performance in such cells.