Design length scales for carbon nanotube photoabsorber based photovoltaic materials and devices

Semiconducting carbon nanotubes are attractive materials for harvesting light in photovoltaic solar cells and photodetectors. A crucial aspect of designing efficient photovoltaic devices using nanotubes is minimizing the length scale for the absorption of light (L-A) and maximizing the length scale across which excitons diffuse (L-D) in fibers and films of these materials. In order to facilitate the optimization of these parameters, here we model how L-A and L-D are affected by nanotube bandgap polydispersity, inter-nanotube coupling, film disorder, orientation, and defects. Our models are guided by previous experimental measurements of optical absorption spectra and exciton inter-nanotube transfer rates made on isolated and bundled nanotubes in conjunction with kinetic Monte Carlo simulations. Our results provide criteria for materials selection and the design of efficient carbon nanotube-based light harvesting devices, in various architectures. (C) 2013 AIP Publishing LLC.