Probing Recombination Mechanism and Realization of
Marcus Normal Region Behavior in DSSCs Employing Cobalt Electrolytes
and Triphenylamine Dyes
Suraj Soman
Sourava C. Pradhan
Muhammed Yoosuf
Manikkedath V. Vinayak
Sivasankaran Lingamoorthy
Karical R. Gopidas
10.1021/acs.jpcc.8b01325.s001
https://acs.figshare.com/articles/journal_contribution/Probing_Recombination_Mechanism_and_Realization_of_Marcus_Normal_Region_Behavior_in_DSSCs_Employing_Cobalt_Electrolytes_and_Triphenylamine_Dyes/6089468
Cobalt
based, outer-sphere, one-electron redox shuttles represents
an exciting class of alternative electrolyte to be used in dye-sensitized
solar cells. The flexibility of redox potential tuning by varying
the substituents on peripheral organic ligands renders them the advantage
of achieving higher photovoltage. However, higher recombination experienced
in these systems by employing diffusion-limited cobalt species serves
as a bottleneck which significantly limits attaining higher performance.
The focus of the present contribution is to systematically investigate
in detail the effect of structural variations and steric hindrance
of organic triphenylamine dyes (TPAA4 and TPAA5) which differs in
the number and nature of binding groups and peripheral hole accepting
units on the recombination reactions and mass transport variations
employing two different cobalt electrolytes, [Co<sub>3</sub>]<sup>3+/2+</sup> and [Co(phen)<sub>3</sub>]<sup>3+/2+</sup>, having variable
driving force for recombination. The detailed photovoltaic analysis
provides us the information that modification of the architecture
of organic dyes plays a decisive role in determining the performance,
in particular, employing alternate one-electron outer-sphere redox
systems. From our analysis, for both the dyes the charge recombination
with the oxidized cobalt species was found to happen in the Marcus
normal region which is attributed to the shift in conduction band
(CB) that influenced the driving force for recombination. The current
observation was quite exciting since the redox systems employed in
the present study were previously documented to exhibit Marcus inverted
recombination behavior. The impact of structural variations of dyes,
change in conduction band, effect of nature of electrolyte species,
and its interaction with the semiconductor on the recombination reactions
was explored in detail using a range of small and large perturbation
techniques.
2018-03-27 00:00:00
recombination reactions
electrolyte
TPAA
dye
conduction band
Marcus
Triphenylamine Dyes Cobalt
diffusion-limited cobalt species
one-electron redox shuttles
CB
one-electron outer-sphere redox systems
DSSCs Employing Cobalt Electrolytes
mass transport variations