Non-covalent functionalisation of single wall carbon nanotubes for efficient dye-sensitised solar cells

A new non-covalent sidewall functionalisation of single wall carbon nanotubes (SWNTs) is proposed in order to use them in the production of dye-sensitised solar cells (DSSCs) with improved properties. 1(hydroxymethyl) pyrene (Py-OH) is irreversibly adsorbed onto the sidewalls of SWNTs via pi-stacking to avoid any chemical modification of SWNTs in an acidic environment. This generally changes the sidewall sp(2) structure of carbon nanotubes and, consequently, their physico-chemical properties. The presence of OH groups in Py-OH allows interaction with cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato) ruthenium(II) dye (N3), commonly used in the fabrication of DSSCs, and the formation of a SWNT/Py-OH/N3 complex. The physico-chemical properties of such complexes are studied and DSSCs are made by using glasses coated with fluorine tin oxide and aluminium film as the electrode and counter-electrode, respectively, with poly(3,4-ethylenedioxythiophene)-poly(styrenesulphonate) as the electron-donor material. The current density vs. voltage curve of such cells is measured and shows the importance of the SWNT/Py-OH/N3 complex in the production of efficient dye-sensitised solar cells. A power efficiency of 6.21% is obtained at AM 1.5 simulated solar intensity. In addition, the new complex can be easily used in the fabrication of DSSC on flexible substrates, as high temperatures are not required. (C) 2014 Elsevier B.V. All rights reserved.