Structural, optoelectronic and charge transport properties of the complexes of indigo encapsulated in carbon nanotubes

Abstract

Using the dispersion-corrected density functional B97D and 6-31g(d,p) basis set, the structural, stability, electronic, optical and charge transport properties of the complexes formed by encapsulating indigo inside carbon nanotubes (CNTs) of varying diameters are investigated. Based on the stabilization energy of the complexes indigo@(n,n)CNT (where n = 6, 7 and 8), indigo@(7,7)CNT is shown to be the most stable owing to the ideal diameter of (7,7)CNT for encapsulating indigo. The nature of the interaction between the guest and the host is investigated by means of energy decomposition analysis employing the symmetry adapted perturbation theory. Electronic properties such as the ionization energy, the electron affinity and the energy gap between the highest occupied and lowest unoccupied molecular orbitals (ΔEH-L) of the complexes are determined. The low values of ΔEH-L (<1 eV) for the complexes suggest that they can act as narrow energy gap semiconductors. All the complexes exhibit high hole and electron mobilities which vary inversely with respect to the diameter of the CNT. Using the time-dependent density functional theoretical method, the absorption properties are predicted for the most stable complex indigo@(7,7)CNT. The presence of charge transfer peaks in the visible and near-infrared regions of the electromagnetic spectrum suggests that the complexes are suitable for optoelectronic devices such as solar cells.

Optoelectronic and charge transport properties of the complex of carbon nanotube with perylene bisimide

“…Such a considerable decrease in Δ E H‐L for the complex is possibly due to the charge transfer between PBI and CNT. Unlike in the studies on indigo‐CNT complexes, the present study demonstrates that energy gap between FMO of CNT alters remarkably on forming complex with PBI. This suggests that PBI has the ability to tune the orbital energy gap.…”

“…The figures clearly illustrate the transfer of electron density from highest occupied molecular orbital (HOMO) delocalized over CNT to LUMO delocalized over PBI suggesting the possibility of photoinduced charge transfer within the complex. Compared to the partial charge transfer from CNT to indigo observed in our earlier studies, herein a complete charge transfer takes place from CNT to PBI. The energy gap between HOMO and LUMO (Δ E H‐L ) of the complex and that of its components were calculated for various functionals and are listed in Table S1.…”

“…The past decade witnessed a rapid development in the functionalization of carbon nanotubes (CNTs) for optoelectronic applications due to their remarkable structural, electronic, optical, and transport properties . The pristine CNTs cannot be used as such due to their tendency to form bundles.…”

“…The past decade witnessed a rapid development in the functionalization of carbon nanotubes (CNTs) for optoelectronic applications due to their remarkable structural, electronic, optical, and transport properties. [1][2][3][4][5][6][7][8][9][10][11] The pristine CNTs cannot be used as such due to their tendency to form bundles. The above problem can be circumvented by different methods such as non-covalent functionalization with organic molecules.…”

New Light on Molecule–Nanotube Hybrids

“…This is in contrast with results obtained by integrating the functional molecule (perylene in this case) directly into the surfactant (Figure 1b). [31] The energy transfer follows the Förster like transfer mechanism while the nanotube-compound distance is well below the Förster radius. In the above examples, carbon nanotubes were functionalized non-covalently but the coupling between nanotube and functional groups is still efficient enough to induce the energy transfer and enhance the optical signals.…”