Environmental Engineering Reference
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Fig. 4.5 (a) The idealized
chemical structures of
graphene and P3OT.
(b) Schematic of the device
with P3OT/graphene thin film
as the active layer and the
structure ITO/PEDOT:PSS
(40 nm)/P3OT:graphene
(100 nm)/LiF (1 nm)/Al
(70 nm). (c) Energy level
diagram of P3OT and
SPFGraphene. (d) Schematic
representation of the reaction
of phenyl isocyanate with
graphene oxide to form SPF
Graphene. (a-d) Reproduced
with permission [ 4 ].
Copyright 2008, Wiley-VCH
Chen et al. have reported the fabrication and comprehensive studies of the BHJ
structure solar cells employing solution processable functionalized graphene (SPF
Graphene) as the acceptor and P3OT as the donor (Fig. 4.5 )[ 4 ]. As shown in
Fig. 4.6 , the strong photoluminescence (PL) of P3OT is remarkably reduced after
the introduction of SPF Graphene, showing that efficient energy transfer occurs
along the P3OT-SPF Graphene interface. The PL quenching behavior has been in
detail studied by Hill et al. through electrochemical studies of GO sheets and
P3HT utilizing a surfactant-assisted method [ 50 ]. The efficient quenching of PL
emission with GO indicates that graphene is a promising electron-accepting
material for OPV applications. SPF Graphene-based solar cells by spin coating a
dichlorobenzene solution with different ratios of SPF Graphene and P3OT have
been studied in details. As shown in Table 4.1 , the performance of the P3OT/
SPFG-based photovoltaic device was much higher than that of the device based on
pristine P3OT, indicating that there was an obvious charge transfer from P3HT
donor to SPFGraphene acceptor. Under simulated 100 mW AM 1.5G illumination,
a PCE of 0.32 % for the P3OT/SPF Graphene-based devices with 5 %
SPFGraphene in the active layer was obtained. After annealing treatment, the
performance of the devices is greatly improved. The device without annealing
treatment had a PCE of only 0.32 %, V oc of 0.56 V, J sc of 2.5 mA/cm 2 , and FF of
0.23. After annealing at 160 C for 20 min, the PCE increased to 1.4 %, with V oc ,
J sc , and FF increasing to 0.92 V, 4.2 mA/cm 2 , and 0.37, respectively. Two factors
should contribute to the improvement of the device performance. During the
annealing process, graphene sheet should be recovered at least partially again with
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