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 (LA) and maximizing the length scale across which excitons diffuse (LD) in fibers and films of these materials. In order to facilitate the optimization of these parameters, here we model how LA and LD 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.