A triblock copolymer consisting of hole-transport, electron-transport, and nanocluster-binding moieties was used in the fabrication of photovoltaic test devices. Depending on the casting solvent used in the device fabrication process, the morphology of the block copolymer in the devices was either an ordered, perpendicular cylindrical phase or a uniformly mixed homogeneous material. The photovoltaic action spectra of these two device types revealed clearly that the charge collection efficiency was influenced favorably by the microphase separation of the ordered system. Underlying mechanisms for these observations are discussed. (C) 2004 Wiley Periodicals, Inc.