NOVELTY - A phase-separable block copolymer comprises a first fully conjugated homopolymer and a second fully conjugated homopolymer, where the first fully conjugated homopolymer comprises a first monomer, where the first monomer comprises a first heterocycle, where the second fully conjugated homopolymer comprises a second monomer, and where the second monomer comprises a second heterocycle chemically distinct from the first heterocycle.    USE - The phase-separable block copolymer is useful for manufacturing optoelectronic device, semiconductor, solar cell, and photovoltaic device; and for arranging set of nanocrystals. The semiconductor composite material is useful for formation of semiconducting film (all claimed).    ADVANTAGE - The invention provides method for controlling optical properties and nanostructure of fully conjugated polymers such that the polymers and composites have applicability to a wide range of electronics applications.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) an optoelectronic device comprising the phase-separable block copolymer; or an optoelectronic device comprising the semiconductor composite material; or an optoelectronic device comprising the semiconductor composite material formed on a substrate and where the film has Ra of less than 3 nm;    (2) a copolymer-nanocrystal composite comprising the phase-separable block copolymer;    (3) an optoelectronic device comprising the copolymer-nanocrystal composite;    (4) a method of arranging a set of nanocrystals comprising: (i) synthesizing the phase-separable block copolymer; (ii) mixing the set of nanocrystals with a solution comprising the phase-separable block copolymer; and (iii) phase separating the phase-separable block copolymer;    (5) a method of adjusting a set of properties of a phase-separable block copolymer where the phase-separable block copolymer comprises a first fully conjugated homopolymer and a second fully conjugated homopolymer, the first fully conjugated homopolymer comprises a first monomer, the first monomer comprises a first heterocycle, the second fully conjugated homopolymer comprises a second monomer, the second monomer comprises a second heterocycle chemically distinct from the first heterocycle, and the method comprise: (i) synthesizing the phase-separable block copolymer; and (ii) phase separating the phase-separable block copolymer;    (6) a semiconductor composite material comprising block copolymer in combination with an electron acceptor material;    (7) a method of manufacturing a semiconductor, comprising providing the semiconductor composite material; and coating a substrate with the semiconductor composite material;    (8) a method of manufacturing a solar cell, comprising providing the semiconductor comprising the semiconductor composite material; and incorporating the semiconductor into the cell; or a method of manufacturing a solar cell comprising providing a semiconductor comprising the semiconductor composite material; and incorporating the semiconductor into the cell;    (9) a solar cell comprising: (i) a cathode and an anode, (ii) an active layer having a first surface and a second surface disposed between the cathode and the anode, and (iii) a titanium dioxide layer formed to be in electrical contact with one of the first surface and the second surface of the active layer, where the active layer comprises a semiconductor composite material; and    (10) a method for making a photovoltaic device, comprising: (i) providing a solution of the block copolymer; and (ii) applying the solution to a substrate; where the temperature of at least one of the solution and substrate is controlled to be at least 40 degrees C during step (ii).