Metastable wurtzstannite Cu2ZnGeS4 (CZGS) nanocrystals were synthesized via a hot-injection method and then used as matrixes to fabricate PtCo-CZGS heterostructured nano-particles. The formed Mott-Schottky heterojunctions in the hybrid nanocrystals promote the transfer of electrons from semiconducting CZGS to metallic PtCo, which accelerates the reduction of I3(-) to I(-) in dye-sensitized solar cells.