Exciton dissociation and carrier transport in poly(3-hexylthiophene) (P3HT)/germanium (Ge) nanocrystals composites were investigated by steady-state and time-resolved photoluminescence (PL) as well as photovoltaic (PV) effect. Quenching of the PL quantum yield η and shortening of the PL lifetime τ in the composites were observed, which were ascribed to rapid exciton dissociate at the interface. PV devices were fabricated based on Ge/P3HT composites sandwiched between indium tin oxide and aluminum. The external quantum efficiency spectrum displayed wide photoresponse range, covering both nanocrystals absorption range and P3HT one. Large open circuit voltage up to 0.45 V and obvious short-circuit current were demonstrated in hybrid Ge nanocrystals/P3HT PV device.