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

The charge interaction and corresponding doping effect between single-walled carbon nanotubes (SWNTs) and various fullerene derivatives, namely, C-60, phenyl-C-61-butyric acid methyl ester (PC61BM), methano-indenefullerene (MIF), 1 ' ,1 '' ,4 ' ,4 '' -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 of SWNTs, is used as a means of investigation. Data from different measurements have to be used to obtain a concrete evaluation for the fullerene-applied SWNTs. The data collectively points toward the conclusion that fullerenes with high molecular orbital energy levels, namely, MIF, SIMEF-1, SIMEF-2, and PC61BM, induce p-type doping, while fullerenes with low molecular orbital energy levels, namely, ICBA and C-60, induce n-type doping on the carbon nanotubes. Nevertheless, the SWNTs retained p-type characteristics because n-doping induced by the fullerenes are weak compared to the p-doping of the water and oxygen on carbon nanotubes. This means that fullerene derivatives have the ability to fine-tune the energy levels of carbon nanotubes, which can play a crucial role in carbon nanotube-based electronics, such as solar cells, light-emitting devices, and FETs.