NOVELTY - A device (10) comprises a substrate (12); and a continuous network of polymer nanostructures coupled to the substrate. The device comprises a mating material in intimate contact with the network of polymer nanostructures to form a high-surface area interface (28) between the network of polymer nanostructures and the mating material. The network of polymer nanostructures comprises one of an electron donor material (24) and an electron acceptor material (26) and the mating material comprises the other of the electron donor material and the electron acceptor material.    USE - As photoactive device (claimed) (such as photovoltaic devices, light-emitting diodes, optically active transistors, optically active organic devices and organic photovoltaic device (OPV)) for a solar cell.    ADVANTAGE - The photovoltaic device exhibits a high active-volume fraction of the morphology between the electron donor material and the electron acceptor material, thereby increase or maximize external quantum efficiency (EQE) of the resulting solar cell.    DETAILED DESCRIPTION - A device (10) comprises a substrate (12); and a continuous network of polymer nanostructures coupled to the substrate. The device comprises a mating material in intimate contact with the network of polymer nanostructures to form a high-surface area interface (28) between the network of polymer nanostructures and the mating material. The network of polymer nanostructures is physisorbed to the substrate in an intimate and conformal coupling between the network of polymer nanostructures and the substrate. The network of polymer nanostructures comprises one of an electron donor material (24) and an electron acceptor material (26) and the mating material comprises the other of the electron donor material and the electron acceptor material. An INDEPENDENT CLAIM is included for making a photoactive device involving mixing a first polymer and a second polymer in a solvent to form a solution in which each of the first polymer and the second polymer is dissolved by the solvent; coating the solution onto a substrate; phase-separating the first polymer from the second polymer to form a continuous network of nanostructures of the first polymer interlinked with a continuous network of nanostructures of the second polymer, forming a high-surface area interface between the continuous network of nanostructures of the first polymer and the continuous network of nanostructures of the second polymer; and removing the second polymer to expose the high-surface area interface.    DESCRIPTION OF DRAWING(S) - The figure shows a conceptualized schematic representation of a device comprising a high-surface area or high-active volume morphology structure.    Device (10)    Substrate (12)    Active layer (22)    Electron donor material (24)    Electron acceptor material (26)    Surface area interface (28)    Photons (30)