16 p-Type Dye Sensitized Solar Cells …
337
liquid electrolytes. Among the p-semiconductors that act as hole transport materials,
CuI plays a key role due to its higher stability and conductivity (Kato et al. 2018).
In 1998, Nature has published a letter by Grätzel putting forward the concept of
a solid state dye-sensitized TiO 2 solar cells that can achieve high photon to electron
conversion efficiency (Li et al. 2006; Bach et al. 1998). In 2014, Lei Zhang et al. fabricated the first solid state p-type dye-sensitized solar cell (p-ssDSC) using the electron
conducting material, phenyl-C61-butyric acid methyl ester (PCBM) in the presence
of NiO semiconductor and organic dye sensitizer. They have observed an admirable
open circuit voltage (V OC = 620 mV) due to the suppression of charge recombination losses. However, the J SC value is very small (50 μA cm
−2 ) due to unsatisfactory
lifetime of the excited state of the dye or slow regeneration of the dye. However, this
attempt intensified the development of tandem solid-state dye-sensitized solar cells
(t-ssDSCs) as well as dye-sensitized solar fuel devices (DSSFDs) (Zhang et al. 2016).
The same group of scientists have developed an Indacenodithieno[3,2-b]thiophene
(IDTT)-based organic dye (TIP) for further improvement of p-ssDSCs by minimizing
the drawbacks of earlier research work. More recent work has produced comparatively higher performance (η = 0.18%; V OC = 550 mV; J SC = 0.86 mA cm
−2 ).
According to the charge lifetime experiments they have revealed that the TIP dye
could significantly minimise recombination losses (Xu et al. 2019).
Lei Tian et al. have developed a core-shell NiO-dye-TiO 2 mesoporous film for
the first time using a newly designed triphenylamine dye. Fabrication of the film
has been done by employing atomic layer deposition technique. In this architecture,
NiO nanoparticles are covered by TiO 2 layer that allows close contact of the dye
and the semiconductor. Further, the dye alignment is well oriented for favourable
electron/hole injection. This fabrication renders efficient and ultra-fast hole injection
into NiO (>98%, ≤200 fs), followed by faster dye regeneration (70–93%, ≤500 fs),
transferring electrons to TiO 2 . This ensures much slower charge recombination than
that in the absence of TiO 2 layer (t1/2 ≈ 100 ps). This is an interesting discovery
which is applicable in ssDSCs (Tian 2019; Tian et al. 2017).
16.11 Summary and Outlook
Dye-sensitized solar cells represent one of the brightest prospects to address the
energy crisis the world is facing. DSCs have the promise of being a commercially
viable renewable energy source, due to the Research throughout the world has been
directed towards a goal of discovering the best combination of components for
DSCs. Currently, p-DSCs have gained attention in this regard, since it entails much
more development to achieve the ultimate goal of fabricating efficient tandem-DSCs
(Table 16.3).
Three major hurdles remain for viable p-DSC device, namely: (1) energy losses
within the device, (2) coloration and high recombination rates of semiconductor
material, and (3) poor light harvesting ability of the photocathode.
337
liquid electrolytes. Among the p-semiconductors that act as hole transport materials,
CuI plays a key role due to its higher stability and conductivity (Kato et al. 2018).
In 1998, Nature has published a letter by Grätzel putting forward the concept of
a solid state dye-sensitized TiO 2 solar cells that can achieve high photon to electron
conversion efficiency (Li et al. 2006; Bach et al. 1998). In 2014, Lei Zhang et al. fabricated the first solid state p-type dye-sensitized solar cell (p-ssDSC) using the electron
conducting material, phenyl-C61-butyric acid methyl ester (PCBM) in the presence
of NiO semiconductor and organic dye sensitizer. They have observed an admirable
open circuit voltage (V OC = 620 mV) due to the suppression of charge recombination losses. However, the J SC value is very small (50 μA cm
−2 ) due to unsatisfactory
lifetime of the excited state of the dye or slow regeneration of the dye. However, this
attempt intensified the development of tandem solid-state dye-sensitized solar cells
(t-ssDSCs) as well as dye-sensitized solar fuel devices (DSSFDs) (Zhang et al. 2016).
The same group of scientists have developed an Indacenodithieno[3,2-b]thiophene
(IDTT)-based organic dye (TIP) for further improvement of p-ssDSCs by minimizing
the drawbacks of earlier research work. More recent work has produced comparatively higher performance (η = 0.18%; V OC = 550 mV; J SC = 0.86 mA cm
−2 ).
According to the charge lifetime experiments they have revealed that the TIP dye
could significantly minimise recombination losses (Xu et al. 2019).
Lei Tian et al. have developed a core-shell NiO-dye-TiO 2 mesoporous film for
the first time using a newly designed triphenylamine dye. Fabrication of the film
has been done by employing atomic layer deposition technique. In this architecture,
NiO nanoparticles are covered by TiO 2 layer that allows close contact of the dye
and the semiconductor. Further, the dye alignment is well oriented for favourable
electron/hole injection. This fabrication renders efficient and ultra-fast hole injection
into NiO (>98%, ≤200 fs), followed by faster dye regeneration (70–93%, ≤500 fs),
transferring electrons to TiO 2 . This ensures much slower charge recombination than
that in the absence of TiO 2 layer (t1/2 ≈ 100 ps). This is an interesting discovery
which is applicable in ssDSCs (Tian 2019; Tian et al. 2017).
16.11 Summary and Outlook
Dye-sensitized solar cells represent one of the brightest prospects to address the
energy crisis the world is facing. DSCs have the promise of being a commercially
viable renewable energy source, due to the Research throughout the world has been
directed towards a goal of discovering the best combination of components for
DSCs. Currently, p-DSCs have gained attention in this regard, since it entails much
more development to achieve the ultimate goal of fabricating efficient tandem-DSCs
(Table 16.3).
Three major hurdles remain for viable p-DSC device, namely: (1) energy losses
within the device, (2) coloration and high recombination rates of semiconductor
material, and (3) poor light harvesting ability of the photocathode.