Investigation of charge interaction between fullerene derivatives and single-walled carbon nanotubes

The charge interaction and corresponding doping effect between single-walled carbonnanotubes (SWNTs) and various fullerene derivatives, namely, C60, phenyl-C61-butyricacid methyl ester (PC61BM), methano-indenefullerene (MIF), 10,100,40,400-tetrahydrodi[1,4]methanonaphthaleno[5,6]fullerene (ICBA), 1,4-bis(dimethylphenylsilylmethyl)[60]fullerene (SIMEF-1), and dimethyl(orthoanisyl) silylmethyl(dimethylphenylsilylmethyl)[60]fullerene (SIMEF-2), are investigated. A variety of analytical techniques,including field-effect transistors (FETs) made of horizontally aligned arrays ofSWNTs, is used as a means of investigation. Data from different measurements haveto be used to obtain a concrete evaluation for the fullerene-applied SWNTs. The datacollectively points toward the conclusion that fullerenes with high molecular orbitalenergy levels, namely, MIF, SIMEF-1, SIMEF-2, and PC61BM, induce p-type doping,while fullerenes with low molecular orbital energy levels, namely, ICBA and C60,induce n-type doping on the carbon nanotubes. Nevertheless, the SWNTs retained ptypecharacteristics because n-doping induced by the fullerenes are weak compared tothe p-doping of the water and oxygen on carbon nanotubes. This means that fullerenederivatives have the ability to fine-tune the energy levels of carbon nanotubes, whichcan play a crucial role in carbon nanotube-based electronics, such as solar cells, lightemittingdevices, and FETs.