Fig. 27e. Figure 27f shows the quasi- photovoltaic effect (i.e., the linear increase
in the photocurrent with the applied bias) measured in the P3HT/MWCNT hybrid
single NT. In the experiments, the short circuit current (I sc ) was measured to
be – 0.67 nA, and the open circuit voltage (V oc ) was measured to be 2.44 mV.
The power conversion efficiency (η) of the P3HT/MWCNT hybrid single NT was
estimated to be ~0.42%.
Nanoscale photovoltaic cells are now considered as potentially new types of
solar energy harvesting nanosystems. A single coaxial silicon NW with a p-type/
intrinsic/n-type (PIN)-doped semiconductor structure has been experimentally
realized as a nanoscale electronic power source [142]. Recently, single NW photovoltaic devices using coaxial NWs consisting of ZnO and P3HT were shown to
exhibit a η value of 0.036% [143]. The nanoscale photovoltaic cells using the
coaxial NWs, composite NWs, or various nanostructures must be studied to fabricate high-efficiency future energy harvesting systems.
Figure 28a shows the fabrication process for the P3HT:PCBM composite NWs
through a wetting method by using Al 2 O 3 nanoporous templates with a pore size of
100 nm [144]. Figure 28b shows the normalized LCM PL spectra (λ ex ¼ 488 nm)
for single NWs of P3HT, PCBM, and P3HT:PCBM composite (1:1 wt%). For
single P3HT NW, the LCM PL peaks corresponding to the 0–0 and 0–1 transitions
of P3HT were observed at 650 and 700 nm, respectively. The LCM PL peak of the
single PCBM NW was observed at 730 nm, with a shoulder peak at 810 nm. For the
single P3HT:PCBM composite NW, the maximum LCM PL peak was observed at
725 nm, with shoulder peaks at 650 and 810 nm, indicating the coexistence of P3HT
and PCBM phases in the single NW.
Figure 28c, d shows a schematic illustration and SEM image of a nanodevice
comprising a single P3HT:PCBM NW with Au and Al electrodes. The IÀV characteristic curve of the single P3HT:PCBM (1:2 wt%) NW in the dark shows diode-like
behavior, as shown in Fig. 28e. Under illumination, the current levels were enhanced
at a relatively high bias (V ! 10 V), as shown in Fig. 28e. Excitons were created in
the major P3HT and minor PCBM components, and they dissociated into electrons
and holes under the applied electric field near the interface between P3HT and
PCBM.
Recently, Lee and coworkers reported the fabrication and nanoscale physical
properties of hybrid P3HT/PCBM NPs and their photovoltaic applications [52].
Figure 29a shows the LCM PL spectra of annealed and non-annealed hybrid NPs of
p-type P3HT and n-type PCBM prepared by the mini-emulsion method [46, 50].
From the wide-angle X-ray diffraction patterns, the annealed P3HT NPs had a lager
crystalline size (~76.5 A ˚ ) than non-annealed NPs (58.8 A ˚ ), as shown in the right
inset of Fig. 29a. The LCM PL intensities of single annealed and non-annealed
hybrid P3HT/PCBM NPs were lower than those of a single annealed P3HT NP, as
shown in Fig. 29a, indicating PL quenching.
Figure 29b shows the scheme of a conducting atomic force microscope (c-AFM)
experiment using a single hybrid P3HT/PCBM NP. An indium tin oxide (ITO)
electrode was used as the cathode because of its relatively low work function
(4.8 eV) compared with that (5.1 eV) of the Pt metal used as the anode. Figure 29c
238
Y.K. Hong et al.
in the photocurrent with the applied bias) measured in the P3HT/MWCNT hybrid
single NT. In the experiments, the short circuit current (I sc ) was measured to
be – 0.67 nA, and the open circuit voltage (V oc ) was measured to be 2.44 mV.
The power conversion efficiency (η) of the P3HT/MWCNT hybrid single NT was
estimated to be ~0.42%.
Nanoscale photovoltaic cells are now considered as potentially new types of
solar energy harvesting nanosystems. A single coaxial silicon NW with a p-type/
intrinsic/n-type (PIN)-doped semiconductor structure has been experimentally
realized as a nanoscale electronic power source [142]. Recently, single NW photovoltaic devices using coaxial NWs consisting of ZnO and P3HT were shown to
exhibit a η value of 0.036% [143]. The nanoscale photovoltaic cells using the
coaxial NWs, composite NWs, or various nanostructures must be studied to fabricate high-efficiency future energy harvesting systems.
Figure 28a shows the fabrication process for the P3HT:PCBM composite NWs
through a wetting method by using Al 2 O 3 nanoporous templates with a pore size of
100 nm [144]. Figure 28b shows the normalized LCM PL spectra (λ ex ¼ 488 nm)
for single NWs of P3HT, PCBM, and P3HT:PCBM composite (1:1 wt%). For
single P3HT NW, the LCM PL peaks corresponding to the 0–0 and 0–1 transitions
of P3HT were observed at 650 and 700 nm, respectively. The LCM PL peak of the
single PCBM NW was observed at 730 nm, with a shoulder peak at 810 nm. For the
single P3HT:PCBM composite NW, the maximum LCM PL peak was observed at
725 nm, with shoulder peaks at 650 and 810 nm, indicating the coexistence of P3HT
and PCBM phases in the single NW.
Figure 28c, d shows a schematic illustration and SEM image of a nanodevice
comprising a single P3HT:PCBM NW with Au and Al electrodes. The IÀV characteristic curve of the single P3HT:PCBM (1:2 wt%) NW in the dark shows diode-like
behavior, as shown in Fig. 28e. Under illumination, the current levels were enhanced
at a relatively high bias (V ! 10 V), as shown in Fig. 28e. Excitons were created in
the major P3HT and minor PCBM components, and they dissociated into electrons
and holes under the applied electric field near the interface between P3HT and
PCBM.
Recently, Lee and coworkers reported the fabrication and nanoscale physical
properties of hybrid P3HT/PCBM NPs and their photovoltaic applications [52].
Figure 29a shows the LCM PL spectra of annealed and non-annealed hybrid NPs of
p-type P3HT and n-type PCBM prepared by the mini-emulsion method [46, 50].
From the wide-angle X-ray diffraction patterns, the annealed P3HT NPs had a lager
crystalline size (~76.5 A ˚ ) than non-annealed NPs (58.8 A ˚ ), as shown in the right
inset of Fig. 29a. The LCM PL intensities of single annealed and non-annealed
hybrid P3HT/PCBM NPs were lower than those of a single annealed P3HT NP, as
shown in Fig. 29a, indicating PL quenching.
Figure 29b shows the scheme of a conducting atomic force microscope (c-AFM)
experiment using a single hybrid P3HT/PCBM NP. An indium tin oxide (ITO)
electrode was used as the cathode because of its relatively low work function
(4.8 eV) compared with that (5.1 eV) of the Pt metal used as the anode. Figure 29c
238
Y.K. Hong et al.