Conventional semi-transparent photovoltaics suffer from an inherent tradeoff between the amount of visible light transmitted versus absorbed, reducing energy conversion efficiency when higher transparency is desired. As a solution to lift this tradeoff, we propose a wavelength and angular selective reflector and demonstrate a potential implementation utilizing high aspect ratio metal nanoparticles. Using the anisotropy in the localized surface plasmon resonance wavelength, the proposed device can selectively harness sunlight incident at an elevated angle, increasing the power conversion efficiency by a factor of 1.44, while maintaining 70 percent optical transparency at normal incidence.

The photoresponse of reversed bilayer organic photovoltaic device based on pentacene and C60 is examined, and the mechanism of photocurrent generation is shown to be different to that in conventional heterojunction devices, with free charge carriers generated at the electrode-organic interfaces rather than the organic heterojunction. This hypothesis is tested with silver nanoclusters incorporated at the organic heterojunction to quench excitons and facilitate recombination of free charge carriers, which shows a predicted increase in Jsc. The large Voc in this reversed cell structure is also rationalized in the context of the model proposed.

A pentacene-C60 bilayer heterojunction organic photovoltaic device with interpenetrating donor-acceptor interface was fabricated by nanoimprinting the pentacene layer prior to C60 deposition. An amorphous silicon substrate nanostructured using an excimer laser was imprinted onto the pentacene layer at high temperature and pressure, using a nanoimprinting lithography system to form a textured pentacene surface. A fivefold improvement in power conversion efficiency was observed due to increased exciton dissociation at the large area heterojunction. Using the proposed technique, highly efficient bilayer large area heterojunction photovoltaics based on small molecule organic materials can be envisaged.