Fermi level shift in carbon nanotubes by dye confinement

Abstract

Dye confinement into carbon nanotube significantly affects the electronic charge density distribution of the final hybrid system. Using the electron-phonon coupling sensitivity of the Raman G-band, we quantify experimentally how charge transfer from thiophene oligomers to single walled carbon nanotube is modulated by the diameter of the nano-container and its metallic or semiconducting character. This charge transfer is shown to restore the electron-phonon coupling into defected metallic nanotubes. For sub-nanometer diameter tube, an electron transfer optically activated is observed when the excitation energy matches the HOMO-LUMO transition of the confined oligothiophene. This electron doping accounts for an important enhancement of the photoluminescence intensity up to a factor of nearly six for optimal confinement configuration. This electron transfer shifts the Fermi level, acting on the photoluminescence efficiency. Therefore, thiophene oligomer encapsulation allows modulating the electronic structure and then the optical properties of the hybrid system.

Carbon Nanotubes for Photovoltaics: From Lab to Industry

“…In a related direction, endohedral filling of the SWCNTs with dye molecules may further extend the light harvesting capability of these solar cells, and photoinduced energy transfer from the organic dye to the s‐SWCNTs has already been observed with PL and photocurrent spectroscopy. [ 89 ] Molecules including quaterthiophene (4T), [ 90 ] squarylium dye (SQ), [ 89a,91 ] p,p′‐dimethylaminonitrostilbene (DANS), [ 92 ] and ferrocenylthiocarbonyl based dyes [ 93 ] have all been placed inside a SWCNT. However, these all require a minimum diameter of SWCNT (≈1.1 nm), [ 91,92 ] known as the sieving diameter, which places them outside the diameter range accessible to C 60 as an acceptor.…”

Diameter-dependent single- and double-file stacking of squaraine dye molecules inside chirality-sorted single-wall carbon nanotubes

“…26 The stacking of dye molecules inside SWCNTs was found to be driven by the combined effect of the mutual interactions of the dyes with each other and the interaction of the dyes with the SWCNT walls. Moreover, the dye stacking configuration not only depends on the SWCNT diameter, 25,27,28 but can also depend on the electronic properties of the surrounding SWCNTs 29 and the exact synthesis conditions used, 30 providing an enormous variety of possible dye@SWCNT combinations. Importantly, for each of these hybrid dye@SWCNT structures, different properties of the encapsulated dye molecules, the SWCNTs, and the combined nanohybrids can be observed.…”

Charge transfer in steam purified arc discharge single walled carbon nanotubes filled with lutetium halides

“…The observed shift of breathing modes of the LuCl 3 @pSWCNTs, LuBr 3 @pSWCNTs and LuI 3 @pSWCNTs towards higher and lower frequencies as well as the significant changes in the intensity as compared with the pSWCNTs may be associated with a doping effect. [30][31][32][33][34][35][36] The RBM band positions in the spectra of LuI 3 @pSWCNTs are more significantly shifted than those of the LuCl 3 @pSWCNTs and LuBr 3 @pSWCNTs. In addition, the bands that are in resonance via E 11 M transitions present higher shifts in the frequencies, comparing LuX 3 @pSWCNTs (X = Cl, Br, I) with pSWCNTs, because the metallic tubes are more sensitive to doping.…”

“…The G-band frequency shifts observed between pSWCNTs and LuX 3 @pSWCNTs (X = Cl, Br, I) can be attributed to doping effects, as we already mentioned in the analyses of the RBM. [30][31][32][33][34][35][36] Comparing the spectra of the pristine and filled samples, a weak shift of the G-band to both higher (blueshift) and lower (redshift) frequencies was observed. The contribution of Gmetallic is the most shifted one because it is more sensitive to doping.…”