TECHNOLOGY FOCUS - POLYMERS - Preferred Components: Terminal ends of each organic polymer chain are covalently linked to both the electrodes. A first portion of each organic polymer chain is a polymer that is an electron acceptor and a second portion of each organic polymer chain is polymer that is an electron donor. The organic polymer chains are aligned with one another. The device (D1) further comprises a layer of nanoparticles arranged so that at least a portion of the organic polymer chains extend through interstices between the nanoparticles. The organic polymer chains each includes a p-n junction and at least a portion the p-n junctions are positioned in interstices between the nanoparticles. A thickness of the layer of nanoparticles is less than 50% of an average distance between a carbon at a first terminal end of each organic polymer chain and a carbon located at a terminal end of each organic polymer chain. The first organic polymer is a semiconducting organic polymer that acts as an electron acceptor and the second organic polymer is a semiconducting organic polymer that acts as an electron donor. The electrode in the device (D2) is transparent to sunlight, where a p-n junction is formed at an interface between the first block and the second block. The device (D2) further comprises a layer of nanoparticles arranged so that the block copolymer extends through interstices between the nanoparticles. The nanoparticles have an average diameter of greater than 5 nm. Preferred Method: The polymerization is resumed so that the polymer chains extend through interstices between the nanoparticles. A first monomer is used in the polymerization of the polymer before the polymerization is paused and a second monomer is used in the polymerization of the polymer after the polymerization is resumed, where the first polymer is different from the second polymer. In the method (M1), fabricating the block copolymer chains on the surface of the electrode includes polymerizing the first block on the electrode followed by polymerizing the second block on the electrode. The method (M1) further comprises bonding the block copolymer chains to a second electrode so that the block copolymer chains are between the first and second electrodes.