Dextran-templating
hydrothermal synthesis of monoclinic WO3 exhibits excellent
specific surface area of ∼110 m2/g and a monomodal
pore distribution with an average pore
diameter of ∼20 nm. Dextran plays a crucial role in generating
porosity on WO3. The role of supporting dextran has been
investigated and found to be crucial to tune the surface area, porosity,
and morphology. The photoluminescence and X-ray photoelectron spectroscopy
studies reveal the existence of oxygen vacancies in substoichiometric
WO3, which creates localized defect states in WO3 as synthesized through this templating method. The highly mesoporous
WO3 has been further
explored as an interfacial cathode buffer layer (CBL) in dye-sensitized
solar cells (DSSCs) and perovskite solar cells (PSCs). A significantly
enhanced photoconversion efficiency has boosted up the performance
of the counter electrode used in traditional DSSC (as platinum) and
PSC (as carbon) devices by ∼48 and ∼29%, respectively.
The electrochemical impedance and incident photon to current conversion
efficiency (IPCE) studies were also analyzed in order to understand
the catalytic behavior of the WO3 interfacial CBL for both
DSSCs and PSCs, respectively. The much higher surface area of WO3 enables rapid electron hopping mechanism, which further benefits
for higher electron mobility, resulting in higher short circuit current.
Through this study, we were able to unequivocally establish the importance
of buffer layer incorporation, which can further help to integrate
the DSSC and PSC devices toward more stable, reliable, and enhanced
efficiency-generating devices. In spite of this, using WO3 constitutes an important step toward the efficiency improvement
of the devices for futuristic photoelectrochromic or self-powered
switchable glazing for low-energy adaptive building integration.