Multiple-patterned nanostructures prepared by synergistically combining block-copolymer lithography with nano-imprinting lithography have been used as back reflectors for enhancing light absorption in organic optoelectronic devices. The multiple-patterned electrodes have significantly boosted the performance of organic photovoltaics and photo transistors, owed to the highly effective light scattering and plasmonic effects, extending the range of their practical applications.