2 research outputs found
Nanocellulose-Assisted Formation of Porous Hematite Nanostructures
We report the formation of porous
iron oxide (hematite) nanostructures
via sol–gel transformations of molecular precursors in the
confined space of self-organized nanocrystalline cellulose (NCC) used
as a shape-persistent template. The obtained structures are highly
porous α-Fe<sub>2</sub>O<sub>3</sub> (hematite) morphologies
with a well-defined anisotropic porosity. The character of the porous
nanostructure depends on the iron salt used as the precursor and the
heat treatment. Moreover, a postsynthetic hydrothermal treatment of
the NCC/iron salt composites strongly affects the crystal growth as
well as the porous nanomorphology of the obtained hematite scaffolds.
We demonstrate that the hydrothermal treatment alters the crystallization
mechanism of the molecular iron precursors, which proceeds via the
formation of anisotropic iron oxyhydroxide species. The nanocellulose
templating technique established here enables the straightforward
fabrication of a variety of mesoporous crystalline iron oxide scaffolds
with defined porous structure and is particularly attractive for the
processing of porous hematite films on different substrates
Passivation of PbS Quantum Dot Surface with l‑Glutathione in Solid-State Quantum-Dot-Sensitized Solar Cells
Surface oxidation of quantum dots
(QDs) is one of the biggest challenges
in quantum dot-sensitized solar cells (QDSCs), because it introduces
surface states that enhance electron–hole recombination and
degrade device performance. Protection of QDs from surface oxidation
by passivating the surface with organic or inorganic layers can be
one way to overcome this issue. In this study, solid-state QDSCs with
a PbS QD absorber layer were prepared from thin mesoporous TiO<sub>2</sub> layers by the successive ionic layer adsorption/reaction
(SILAR) method. Spiro-OMeTAD was used as the organic p-type hole transporting
material (HTM). The effects on the solar cell performance of passivating
the surface of the PbS QDs with the tripeptide l-glutathione
(GSH) were investigated. Current–voltage characteristics and
external quantum efficiency measurements of the solar cell devices
showed that GSH-treatment of the QD-sensitized TiO<sub>2</sub> electrodes
more than doubled the short circuit current and conversion efficiency.
Impedance spectroscopy, intensity-modulated photovoltage and photocurrent
spectroscopy analysis of the devices revealed that the enhancement
in solar cell performance of the GSH-treated cells originates from
improved charge injection from PbS QDs into the conduction band of
TiO<sub>2</sub>. Time-resolved photoluminescence decay measurements
show that passivation of the surface of QDs with GSH ligands increases
the exciton lifetime in the QDs