A dye-sensitized semiconductor includes a semiconductor, and a copper(I) coordination compound comprising 2,9-dialkyl-diphenyl-1,10-phenanthrolinedisulfonate, on the semiconductor. The dye-sensitized semiconductor may be used as part of a photoanode in a solar cell, which also contains a counter-electrode, and a conductive medium containing a redox-active mediator, in contact with and separating the photoanode and the counter-electrode.