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 inorder 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 p-stacking toavoid any chemical modification of SWNTs in an acidic environment. This generally changes the sidewallsp2 structure of carbon nanotubes and, consequently, their physico-chemical properties. The presence ofeOH groups in Py-OH allows interaction with cis-bis(isothiocyanato)bis(2,20-bipyridyl-4,40-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 madeby using glasses coated with fluorine tin oxide and aluminium film as the electrode and counterelectrode,respectively, with poly(3,4-ethylenedioxythiophene)epoly(styrenesulphonate) as theelectron-donor material. The current density vs. voltage curve of such cells is measured and shows theimportance of the SWNT/Py-OH/N3 complex in the production of efficient dye-sensitised solar cells. Apower efficiency of 6.21% is obtained at AM 1.5 simulated solar intensity. In addition, the new complexcan be easily used in the fabrication of DSSC on flexible substrates, as high temperatures are not required.