2 research outputs found
A Chemometric Approach for the Sensitization Procedure of ZnO Flowerlike Microstructures for Dye-Sensitized Solar Cells
In
this paper, a methodology for the streamlining of the sensitization
procedure of flowerlike ZnO nanostructures for dye-sensitized solar
cells (DSCs) is reported. The sensitization of ZnO surface with ruthenium-based
complexes is a particularly critical process, since one has to minimize
the dissolution of surface Zn atoms by the protons released from the
dye molecules, leading to the formation of Zn<sup>2+</sup>/dye complexes.
The fine-tuning of the experimental parameters, such as the dye loading
time, the dye concentration, and the pH of the sensitizing solution,
performed through a multivariate optimization by means of a chemometric
approach, is here reported. The dye loading procedure was optimized
using ZnO microparticles with nanostructured protrusions, synthesized
by a simple and low-cost hydrothermal process. Mild reaction conditions
were used, and wurtzite-like crystalline structure with a relatively
high surface area was obtained once the reaction process was completed.
After dispersion of ZnO flowerlike particles in an acetic acid-based
solution, a 14 μm-thick ZnO layer acting as DSC photoanode was
fabricated. The optimized sensitization procedure allowed minimizing
the instability of ZnO surface in contact with acidic dyes, avoiding
the formation of molecular agglomerates unable to inject electrons
in the ZnO conduction band, achieving good results in the photoconversion
efficiency. Moreover, the photoharvesting properties were further
enhanced by adding <i>N</i>-methylbenzimidazole into the
iodine-based liquid electrolyte. Such an additive was proposed here
for the first time in combination with a ZnO photoelectrode, helping
to reduce an undesired recombination between the photoinjected electrons
and the oxidized redox mediator
First Pseudohalogen Polymer Electrolyte for Dye-Sensitized Solar Cells Promising for <i>In Situ</i> Photopolymerization
The incorporation of selenocianated-based
redox couple in a polymer
electrolyte for dye-sensitized solar cells is reported for the first
time. The pseudohalogen redox mediator was integrated in two kinds
of acrylic/methacrylic membranes prepared by photocopolymerization
of multifunctional monomers. Before activation, the obtained membranes
were transparent, self-standing and flexible, and the physicochemical
characterizations of the films showed the formation of highly crosslinked
architectures. Membranes were activated by swelling in an optimized
solution containing the SeCN<sup>–</sup>/(SeCN)<sub>2</sub> redox mediator with 4-<i>tert</i>-butylpyridine in acetonitrile,
and the electrochemical behavior of the electrolytes revealed fast
charge transfer kinetics. The photovoltaic performances of quasi-solid
dye-sensitized solar cells were evaluated and compared with the results
of the liquid counterpart, showing promising photoharvesting properties.
No diminution in photoconversion efficiencies was evidenced in the
comparison between solid and liquid cells, demonstrating an optimal
kinetics of the redox species in the polymer cage, associated with
a noteworthy increase in device durability, as demonstrated by aging
tests. In addition, the <i>in situ</i> photopolymerization
in the presence of the redox mediator is presented with outstanding
results: this process, hardly feasible for the traditional I<sup>–</sup>/I<sub>3</sub><sup>–</sup> couple (inhibitor of radical polymerization
processes), enables at the same time the creation of an excellent
electrode/electrolyte interface and the sealing of the device