Investigation of dye-sensitized solar cell performance with single chirality semiconducting carbon nanotubes

Abstract

In this work, the performance, electrical transport, and optical properties of dye-sensitized solar cells (DSSCs) assembled with single-walled carbon nanotubes (SWNTs) of a single chirality in the photoanode were investigated. Single-chirality carbon nanotubes (CNTs) allow a selection of band-gap and electron mobility. Separating a specific chirality from a mixture of carbon nanotubes remains challenging task. Among separation techniques, one of the most promising is size-exclusion gel chromatography. Although SWNTs separated by this technique has been applied in bulk heterojunction solar cells and other basic electronics, no one has attempted to use this material in DSSCs. Single-chirality carbon nanotubes allow adjustment of the Schottky barrier height at the TiO2/CNT/FTO interface and the presence of single-chirality bundles increases electron diffusion in the photoanode. Furthermore, chirality separated CNTs are expected to absorb less light than mixed chirality CNTs which results in better light absorption and electron injection into the TiO2. Chiralities (6,5) and (7,3) have been separated using this technique and compared with mixed chiralities in a DSSC. Characterization includes I-V curves (performed in dark and light), quantum efficiency, and impedance spectroscopy.