Co-grafting an amphiphilic polypyridyl ruthenium sensitizer and 1-decylphosphonic acid on TiO2 semiconductor nanocrystals has resulted in a long-term thermally stable dye-sensitized solar cell (see Figure) with higher than 7 % power conversion efficiency. The extraordinary stability of this high-efficiency device under both thermal stress and light soaking matches the durability criteria for outdoor applications of solar cells.