Theoretical study of carbon nanotubes as candidates for 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 achieve-ments - 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.

Automated summary

This article presents theoretical calculations of electronic and optical properties for 35 finite Carbon NanoTubes (CNTs) and discusses the possibility of using CNTs as an active layer in organic solar cells. The study finds that CNTs have a large exciton diffusion length, making them suitable for constructing high-efficiency OSCs. Additionally, the parallel ordering of CNTs maximizes the advantage of the large exciton length. Therefore, this research contributes to improving the efficiency of OSCs.