Theoretical study of carbon nanotubes as candidates for active layer in solar cells

• Computation of IR and visible spectra of carbon nanotubes to prove their applicability as an active layer in solar cells. We present results of theoretical calculations of electronic and optical properties for 35 finite Carbon NanoTubes (CNTs). The quantities calculated are: HOMO and LUMO energies, energy gaps, and, most important, visible and infrared spectra. Calculations were performed in DFT and TDDFT formalism. The motivation of this study was examination of possibility of application of CNTs as an active layer in organic solar cells (OSCs). We propose to use CNTs as an active layer for their exceptional property, namely, large exciton diffusion length . This opportunity would allow to construct an OSC in a layer architecture, where thickness of the layer could be sufficient for an absorption of significant part of light and, at the same time, large exciton diffusion length would preserve effectiveness of excitons dissociation into charges. An important aspect is that CNTs should be parallelly ordered in order to maximize the advantage of large exciton length. This way, we hope to radically improve the OSC efficiency and to overcome Bulk HeteroJunction (BHJ) architecture limitations, where – besides last achievements – the efficiency is still substantially lower than theoretical predictions. Our calculations show that overall absorption of CNTs is large in visible and infrared regions. This opportunity imply that necessary condition for construction of layer high-efficient CNT-based OSCs is fulfilled.