A facile solution-phase route was developed to synthesize a family of monodisperse Cu2Ge(S3-xSex) alloyed nanocrystals (NCs) with controlled composition across the entire range (0 <= x <= 3). The band gaps of the resultant NCs can be engineered by tuning the compositions with a nearly linear relationship between them. The band structures of the NCs were studied by cyclic voltammetry and UV-vis absorption spectroscopy. The conducting behavior was revealed to be p-type. for these NCs by photoelectrochemical measurements. Their photovoltaic applicability was finally assessed by fabricating solar cells with the Cu2Ge(S2Se) NCs as light harvester and CdS nanorods as electron conducting materials.