16 p-Type Dye Sensitized Solar Cells …
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consequence, it is hypothesized, that chemical bonds are not involve in photoinduced
charge transfer between the excited KuQ dyes and the NiO electrode, instead, it
occurs through space. The KuQ-sensitized cells have a V OC of 92.2 mV, J SC of
0.74 mA cm
−2 , FF of 35.9 and efficiency of 0.025% (Bonomo et al. 2017b).
16.9 Minimizing Electron Losses
After photoexcitation and injection of charge carriers into the semiconductor material by the photosensitizer, fast dye recombination, comparatively slow regeneration
and lower charge mobility in the semiconductor material can contribute to loss of
electrons within a DSC. Proper manipulation of the electrolyte and the semiconductor material could improve photoconversion efficiency. Novel electrolytes have been
invented that could minimize the electron losses ensuring fast dye regeneration and
minimum recombinations.
Powar et al. have fabricated efficient p-DSCs based on Tris(1,2-diaminoethane)
Cobalt (II)/(III) electrolytes. They have observed [Co(en) 3 ]
2+/3+ redox couple could
render energy conversion efficiencies of 1.3% at 100% sun (1.67% at 10% sun), with
among the best performance indicators to date (V OC = 709 mV, J SC = 4.44 mA cm
−2 ;
FF = 0.42). It is a transparent electrolyte, which can be easily applied into tandem
DSCs. This electrolyte is best applicable with the NiO semiconductor; when it was
used with TiO 2 the V OC obtained was at a level around 475 mV (Powar et al. 2013).
Perera et al. have discovered a novel electrolyte based on tris(acetylacetonato)iron (III)/(II) redox couple ([Fe(acac) 3 ]
0/1− ) for p-DSCs. Interestingly they have
improved the photocurrent by introducing a blocking layer on top of the NiO semiconductor material in the working electrode and by using chenodeoxycholic acid
in the electrolyte. The device fabrication was done by incorporating perylene–thiophene–triphenylamine (PMI–6T–TPA) as the sensitizer and ([Fe(acac) 3 ]
0/1− ) as the
electrolyte. The best reported short circuit of J SC = 7.65 mA cm
−2 up to date has
been achieved by them along with η = 2.51%, FF = 0.51, V OC = 645 mV. When
analysing the measurement of dye regeneration kinetics of the redox mediator, the
rate constant obtained (1.7 × 10
8 M
−1 s
−1 ) is close to the maximum theoretical rate
constant of 3.3 × 10
8 M
−1 s
−1 . As a result, considerably high dye-regeneration yield
(>99%) has been obtained by these devices (Perera et al. 2015).
Xu et al. have introduced disulfide/thiolate electrolytes to improve the efficiency
of p-DSCs. An organic redox couple of 1-methyl-1H-tetrazole-5-thiolate (T) and its
disulfide dimer (T2) redox shuttle were used as an electrolyte in a p-DSC, of CuCrO 2
electrode and an organic dye (P1) sensitizer. Using this iodide-free transparent redox
electrolyte with the sensitized heterojunction, they have gained a comparatively high
V OC of over 300 mV. And also studied on the application of CoS as the counter
electrode and have observed an efficiency of 0.23%. This can be considered as the
maximum efficiency gained for an organic redox couple (Xu et al. 2013).
331
consequence, it is hypothesized, that chemical bonds are not involve in photoinduced
charge transfer between the excited KuQ dyes and the NiO electrode, instead, it
occurs through space. The KuQ-sensitized cells have a V OC of 92.2 mV, J SC of
0.74 mA cm
−2 , FF of 35.9 and efficiency of 0.025% (Bonomo et al. 2017b).
16.9 Minimizing Electron Losses
After photoexcitation and injection of charge carriers into the semiconductor material by the photosensitizer, fast dye recombination, comparatively slow regeneration
and lower charge mobility in the semiconductor material can contribute to loss of
electrons within a DSC. Proper manipulation of the electrolyte and the semiconductor material could improve photoconversion efficiency. Novel electrolytes have been
invented that could minimize the electron losses ensuring fast dye regeneration and
minimum recombinations.
Powar et al. have fabricated efficient p-DSCs based on Tris(1,2-diaminoethane)
Cobalt (II)/(III) electrolytes. They have observed [Co(en) 3 ]
2+/3+ redox couple could
render energy conversion efficiencies of 1.3% at 100% sun (1.67% at 10% sun), with
among the best performance indicators to date (V OC = 709 mV, J SC = 4.44 mA cm
−2 ;
FF = 0.42). It is a transparent electrolyte, which can be easily applied into tandem
DSCs. This electrolyte is best applicable with the NiO semiconductor; when it was
used with TiO 2 the V OC obtained was at a level around 475 mV (Powar et al. 2013).
Perera et al. have discovered a novel electrolyte based on tris(acetylacetonato)iron (III)/(II) redox couple ([Fe(acac) 3 ]
0/1− ) for p-DSCs. Interestingly they have
improved the photocurrent by introducing a blocking layer on top of the NiO semiconductor material in the working electrode and by using chenodeoxycholic acid
in the electrolyte. The device fabrication was done by incorporating perylene–thiophene–triphenylamine (PMI–6T–TPA) as the sensitizer and ([Fe(acac) 3 ]
0/1− ) as the
electrolyte. The best reported short circuit of J SC = 7.65 mA cm
−2 up to date has
been achieved by them along with η = 2.51%, FF = 0.51, V OC = 645 mV. When
analysing the measurement of dye regeneration kinetics of the redox mediator, the
rate constant obtained (1.7 × 10
8 M
−1 s
−1 ) is close to the maximum theoretical rate
constant of 3.3 × 10
8 M
−1 s
−1 . As a result, considerably high dye-regeneration yield
(>99%) has been obtained by these devices (Perera et al. 2015).
Xu et al. have introduced disulfide/thiolate electrolytes to improve the efficiency
of p-DSCs. An organic redox couple of 1-methyl-1H-tetrazole-5-thiolate (T) and its
disulfide dimer (T2) redox shuttle were used as an electrolyte in a p-DSC, of CuCrO 2
electrode and an organic dye (P1) sensitizer. Using this iodide-free transparent redox
electrolyte with the sensitized heterojunction, they have gained a comparatively high
V OC of over 300 mV. And also studied on the application of CoS as the counter
electrode and have observed an efficiency of 0.23%. This can be considered as the
maximum efficiency gained for an organic redox couple (Xu et al. 2013).