2 research outputs found
Influence of TiO<sub>2</sub> Particle Size on Dye-Sensitized Solar Cells Employing an Organic Sensitizer and a Cobalt(III/II) Redox Electrolyte
Dye-sensitized
solar cells (DSSCs) are highly efficient and reliable
photovoltaic devices that are based on nanostructured semiconductor
photoelectrodes. From their inception in 1991, colloidal TiO<sub>2</sub> nanoparticles (NPs) with the large surface area have manifested
the highest performances and the particle size of around 20 nm is
generally regarded as the optimized condition. However, though there
have been reports on the influences of particle sizes in conventional
DSSCs employing iodide redox electrolyte, the size effects in DSSCs
with the state-of-the-art cobalt electrolyte have not been investigated.
In this research, systematic analyses on DSSCs with cobalt electrolytes
are carried out by using various sizes of NPs (20–30 nm), and
the highest performance is obtained in the case of 30 nm sized TiO<sub>2</sub> NPs, indicating that there is a reversed power conversion
efficiency trend when compared with those with the iodide counterpart.
Detailed investigations on various factorsî—¸light harvesting,
charge injection, dye regeneration, and charge collectionî—¸reveal
that TiO<sub>2</sub> particles with a size range of 20–30 nm
do not have a notable difference in charge injection, dye regeneration,
and even in light-harvesting efficiency. It is experimentally verified
that the superior charge collection property is the sole origin of
the higher performance, suggesting that charge collection should be
prioritized for designing nanostructured TiO<sub>2</sub> photoelectrodes
for DSSCs employing cobalt redox electrolytes
Highly Efficient Bifacial Dye-Sensitized Solar Cells Employing Polymeric Counter Electrodes
Dye-sensitized
solar cells (DSCs) are promising solar energy conversion
devices with aesthetically favorable properties such as being colorful
and having transparent features. They are also well-known for high
and reliable performance even under ambient lighting, and these advantages
distinguish DSCs for applications in window-type building-integrated
photovoltaics (BIPVs) that utilize photons from both lamplight and
sunlight. Therefore, investigations on bifacial DSCs have been done
intensively, but further enhancement in performance under back-illumination
is essential for practical window-BIPV applications. In this research,
highly efficient bifacial DSCs were prepared by a combination of electropolymerized
polyÂ(3,4-ethylenedioxythiphene) (PEDOT) counter electrodes (CEs) and
cobalt bipyridine redox ([CoÂ(bpy)<sub>3</sub>]<sup>3+/2+</sup>) electrolyte,
both of which manifested superior transparency when compared with
conventional Pt and iodide counterparts, respectively. Keen electrochemical
analyses of PEDOT films verified that superior electrical properties
were achievable when the thickness of the film was reduced, while
their high electrocatalytic activities were unchanged. The combination
of the PEDOT thin film and [CoÂ(bpy)<sub>3</sub>]<sup>3+/2+</sup> electrolyte
led to an unprecedented power conversion efficiency among bifacial
DSCs under back-illumination, which was also over 85% of that obtained
under front-illumination. Furthermore, the advantage of the electropolymerization
process, which does not require an elevation of temperature, was demonstrated
by flexible bifacial DSC applications