Photovoltaic devices and techniques for enhancing efficiency thereof are provided. In one aspect, a photovoltaic device is provided. The photovoltaic device comprises a photocell having a first photoactive layer and a second photoactive layer adjacent to the first photoactive layer so as to form a heterojunction between the first photoactive layer and the second photoactive layer; and a plurality of high-aspect-ratio nanostructures on one or more surfaces of the second photoactive layer. The plurality of high-aspect-ratio nanostructures are configured to act as a scattering media for incident light. The plurality of high-aspect-ratio nanostructures can also be configured to create an optical resonance effect in the incident light.