1 research outputs found
Photocurrent Quantum Yield of Semiconducting Carbon Nanotubes: Dependence on Excitation Energy and Exciton Binding Energy
We address the dependence of the
relative photocurrent quantum
yield (QY) on the excitation energy and the exciton binding energy
of semiconducting single-walled carbon nanotubes (s-SWNTs) having
well-defined chiral indexes, by analyzing both the optical absorption
and the photocurrent spectra. First, we examine the QY of a sample
consisting of one sort of nanotube (such as (7,5)), which allows revealing
that QY depends on the excitation energy and hence on the nature of
the electronic transition. In particular, we demonstrate that the
QY of the second excitonic transition (<i>E</i><sub>22</sub>) is relatively higher than that of the first excitonic transition
(<i>E</i><sub>11</sub>). Then, we extend the analysis to
a sample consisting of five kinds of nanotubes (namely, (7,5), (7,6),
(8,6), (8,7), (9,7)), which permits demonstrating for the first time
that QY increases with increasing the nanotube’s diameter and
with decreasing the exciton binding energy, according to two categories
known as type 1 and type 2 nanotubes. Finally, we discuss these results
in the framework of the electric-field-assisted exciton dissociation
model in order to gain further insight into the photocarrier generation
mechanism in s-SWNTs