330
S. Peiris et al.
for these dyes. Thus, it is more compatible with other redox mediators allowing high
open circuit voltage. From the three iridium complexes investigated, IrDPQCN2
shows higher photovoltaic performances (V OC = 508 mV; J SC = 0.25 mA cm
−2 , ff
= 0.54; η = 0.068%) (Gennari et al. 2014).
Squaraines (SQs) are a novel group of sensitizers that have the potential to be used
in p-DSCs. They are derived from squaric acid and generate intramolecular donoracceptor-donor charge transfer state in both the ground and the excited states (Law
and Bailey 1992). Squaraines have extremely high molar extinction coefficients, and
intense narrow absorbance/fluorescence in the red-IR. Since the reactivity of the
electrophilic cyclobutyl core is high, SQs easily react with nucleophiles, as well
as bases, limiting the application possibilities. However, recent modifications have
made them more stable (Jiang et al. 2014).
Three squaraines (VG1-C8, VG10-C8, VG11-C) have been synthesised and
applied in p-DSCs by Matteo Bonomo and coworkers. Among the three dyes, VG11C8 with a dicyano–vinyl substituent on the central squaric ring, produces comparatively higher conversion efficiency, than the other two dyes (V OC = 93 mV; J SC =
1.16 mA cm
−2 ; FF = 0.36; η = 0.043%). This yields favourable external quantum
efficiency (EQE) of NiO and imbues characteristics of lower resistance of charge
transport, low interfacial recombination, shorter hole diffusion times, and larger hole
diffusion coefficient, in comparison to other two dyes (Bonomo et al. 2016).
A novel class of quinoid compounds known as KuQuinones (see Fig. 16.12) have
been applied to p-DSCs. The presence of a highly conjugated pentacyclic structure
results in a broad absorption in the visible region with two intense bands between
450 and 630 nm, making them worthy candidates for light harvesting in p-DSCs. In
addition, these dyes consist of a very low reduction potential (Sabuzi et al. 2016).
Bonomo and co-investigators have also incorporated KuQuinones (KuQ) as the
sensitizer in NiO based pDSCs. They state the dye possesses HOMO/LUMO states
that match with the redox potential of I
− /I 3
− and the upper edge of the NiO valence
band. They have reported on KuQ substituted with carboxylic acid and with different
alkyl chain. According to the results KuQ-sensitized cells show similarity to that of
the benchmark sensitizer erythrosine B (Ery B) other than the absence of electronic
conjugation between the light absorbing unit and the anchoring group. Due to this
Fig. 16.12 General structure
of KuQuinones
S. Peiris et al.
for these dyes. Thus, it is more compatible with other redox mediators allowing high
open circuit voltage. From the three iridium complexes investigated, IrDPQCN2
shows higher photovoltaic performances (V OC = 508 mV; J SC = 0.25 mA cm
−2 , ff
= 0.54; η = 0.068%) (Gennari et al. 2014).
Squaraines (SQs) are a novel group of sensitizers that have the potential to be used
in p-DSCs. They are derived from squaric acid and generate intramolecular donoracceptor-donor charge transfer state in both the ground and the excited states (Law
and Bailey 1992). Squaraines have extremely high molar extinction coefficients, and
intense narrow absorbance/fluorescence in the red-IR. Since the reactivity of the
electrophilic cyclobutyl core is high, SQs easily react with nucleophiles, as well
as bases, limiting the application possibilities. However, recent modifications have
made them more stable (Jiang et al. 2014).
Three squaraines (VG1-C8, VG10-C8, VG11-C) have been synthesised and
applied in p-DSCs by Matteo Bonomo and coworkers. Among the three dyes, VG11C8 with a dicyano–vinyl substituent on the central squaric ring, produces comparatively higher conversion efficiency, than the other two dyes (V OC = 93 mV; J SC =
1.16 mA cm
−2 ; FF = 0.36; η = 0.043%). This yields favourable external quantum
efficiency (EQE) of NiO and imbues characteristics of lower resistance of charge
transport, low interfacial recombination, shorter hole diffusion times, and larger hole
diffusion coefficient, in comparison to other two dyes (Bonomo et al. 2016).
A novel class of quinoid compounds known as KuQuinones (see Fig. 16.12) have
been applied to p-DSCs. The presence of a highly conjugated pentacyclic structure
results in a broad absorption in the visible region with two intense bands between
450 and 630 nm, making them worthy candidates for light harvesting in p-DSCs. In
addition, these dyes consist of a very low reduction potential (Sabuzi et al. 2016).
Bonomo and co-investigators have also incorporated KuQuinones (KuQ) as the
sensitizer in NiO based pDSCs. They state the dye possesses HOMO/LUMO states
that match with the redox potential of I
− /I 3
− and the upper edge of the NiO valence
band. They have reported on KuQ substituted with carboxylic acid and with different
alkyl chain. According to the results KuQ-sensitized cells show similarity to that of
the benchmark sensitizer erythrosine B (Ery B) other than the absence of electronic
conjugation between the light absorbing unit and the anchoring group. Due to this
Fig. 16.12 General structure
of KuQuinones