4 research outputs found
One-Step Thermal Gradient- and Antisolvent-Free Crystallization of All-Inorganic Perovskites for Highly Efficient and Thermally Stable Solar Cells.
All-inorganic perovskites have emerged as promising photovoltaic materials due to their superior thermal stability compared to their heat-sensitive hybrid organic-inorganic counterparts. In particular, CsPbI2 Br shows the highest potential for developing thermally-stable perovskite solar cells (PSCs) among all-inorganic compositions. However, controlling the crystallinity and morphology of all-inorganic compositions is a significant challenge. Here, a simple, thermal gradient- and antisolvent-free method is reported to control the crystallization of CsPbI2 Br films. Optical in situ characterization is used to investigate the dynamic film formation during spin-coating and annealing to understand and optimize the evolving film properties. This leads to high-quality perovskite films with micrometer-scale grain sizes with a noteworthy performance of 17% (≈16% stabilized), fill factor (FF) of 80.5%, and open-circuit voltage (VOC ) of 1.27 V. Moreover, excellent phase and thermal stability are demonstrated even after extreme thermal stressing at 300 °C
Topochemical Fluorination of LaBaInO4 to LaBaInO3F2, their Optical Characterization and Photocatalytic Activities for Hydrogen Evolution
We report on a non-oxidative topochemical route for the synthesis of a novel indate-based oxyfluoride, LaBaInO3F2, using a low-temperature reaction of Ruddlesden–Popper-type LaBaInO4 with polyvinylidene difluoride as a fluorinating agent. The reaction involves the replacement of oxide ions with fluoride ions as well as the insertion of fluoride ions at interstitial sites. From the characterization via powder X-ray diffraction (PXRD) and Rietveld analysis as well as automated electron diffraction tomography (ADT) it is deduced that the fluorination results in a symmetry lowering from I4/mmm (139) to monoclinic C2/c (15) with an expansion perpendicular to the perovskite layers and a strong tilting of the octahedra in the ab plane. Disorder of the anions on the apical and the interstitial sites seems to be favored. The most stable configuration for the anion ordering is estimated based on an evaluation of bond distances from the ADT measurements via bond valence sums (BVSs). The observed disordering of the anions in the oxyfluoride results in changes of the optical properties and thus shows that the topochemical anion modification can present a viable route to alter optical properties. Partial densities of states (PDOSs) obtained from ab initio density functional theory (DFT) calculations reveal a bandgap modification upon fluoride-ion introduction which originates from the presence of the oxide anions on the interstitial sites. The photocatalytic performance of the oxide and oxyfluoride shows that both of the materials are photocatalytically active for hydrogen (H2) evolution
Topochemical Fluorination of LaBaInO<sub>4</sub> to LaBaInO<sub>3</sub>F<sub>2</sub>, Their Optical Characterization, and Photocatalytic Activities for Hydrogen Evolution
We report on a nonoxidative topochemical
route for the synthesis
of a novel indate-based oxyfluoride, LaBaInO3F2, using a low-temperature reaction of Ruddlesden–Popper-type
LaBaInO4 with polyvinylidene difluoride as a fluorinating
agent. The reaction involves the replacement of oxide ions with fluoride
ions as well as the insertion of fluoride ions into the interstitial
sites. From the characterization via powder X-ray diffraction (PXRD)
and Rietveld analysis as well as automated electron diffraction tomography
(ADT), it is deduced that the fluorination results in a symmetry lowering
from I4/mmm (139) to monoclinic C2/c (15) with an expansion perpendicular
to the perovskite layers and a strong tilting of the octahedra in
the ab plane. Disorder of the anions on the apical
and interstitial sites seems to be favored. The most stable configuration
for the anion ordering is estimated based on an evaluation of bond
distances from the ADT measurements via bond valence sums (BVSs).
The observed disordering of the anions in the oxyfluoride results
in changes in the optical properties and thus shows that the topochemical
anion modification can present a viable route to alter the optical
properties. Partial densities of states (PDOSs) obtained from ab initio
density functional theory (DFT) calculations reveal a bandgap modification
upon fluoride-ion introduction which originates from the presence
of the oxide anions on the interstitial sites. The photocatalytic
performance of the oxide and oxyfluoride shows that both materials
are photocatalytically active for hydrogen (H2) evolution