The use of layered perovskites is an important strategy to improve the stability of hybrid perovskite materials and their optoelectronic devices. However, tailoring their properties requires accurate structure determination at the atomic scale, which is a challenge for conventional diffraction-based techniques. We demonstrate the use of nuclear magnetic resonance (NMR) crystallography in determining the structure of layered hybrid perovskites for a mixed-spacer model composed of 2-phenylethylammonium (PEA + ) and 2-(perfluorophenyl)ethylammonium (FEA + ) moieties, revealing nanoscale phase segregation. Moreover, we illustrate the application of this structure in perovskite solar cells with power conversion efficiencies that exceed 21%, accompanied by enhanced operational stability.
Layered
hybrid perovskites based on Dion–Jacobson phases
are of interest to various optoelectronic applications. However, the
understanding of their structure–property relationships remains
limited. Here, we present a systematic study of Dion–Jacobson
perovskites based on (S)PbX4 (n = 1) compositions
incorporating phenylene-derived aromatic spacers (S) with different
anchoring alkylammonium groups and halides (X = I, Br). We focus our
study on 1,4-phenylenediammonium (PDA), 1,4-phenylenedimethylammonium
(PDMA), and 1,4-phenylenediethylammonium (PDEA) spacers. Systems based
on PDA did not form a well-defined layered structure, showing the
formation of a 1D structure instead, whereas the extension of the
alkyl chains to PDMA and PDEA rendered them compatible with the formation
of a layered structure, as shown by X-ray diffraction and solid-state
NMR spectroscopy. In addition, the control of the spacer length affects
optical properties and environmental stability, which is enhanced
for longer alkyl chains and bromide compositions. This provides insights
into their design for optoelectronic applications.
Gas diffusion electrodes are essential components of common fuel and electrolysis cells but are typically made from graphitic carbon or metallic materials, which do not allow light transmittance and thus limit the development of gas‐phase based photoelectrochemical devices. Herein, the simple and scalable preparation of F‐doped SnO2 (FTO) coated SiO2 interconnected fiber felt substrates is reported. Using 2–5 µm diameter fibers at a loading of 4 mg cm−2, the resulting substrates have porosity of 90%, roughness factor of 15.8, and Young's Modulus of 0.2 GPa. A 100 nm conformal coating of FTO via atmospheric chemical vapor deposition gives sheet resistivity of 20 ± 3 Ω sq−1 and loss of incident light of 41% at illumination wavelength of 550 nm. The coating of various semiconductors on the substrates is established including Fe2O3 (chemical bath deposition), CuSCN and Cu2O (electrodeposition), and conjugated polymers (dip coating), and liquid‐phase photoelectrochemical performance commensurate with flat FTO substrates is confirmed. Finally, gas phase H2 production is demonstrated with a polymer semiconductor photocathode membrane assembly at 1‐Sun photocurrent density on the order of 1 mA cm−2 and Faradaic efficiency of 40%.
Arene–perfluoroarene moieties are used to assemble Dion-Jacobson perovskite phases, revealing nanosegregation and enhanced environmental stabilities relevant to their application.
Organic materials can tune the optical properties in
layered (2D)
hybrid perovskites, although their impact on photophysics is often
overlooked. Here, we use transient absorption spectroscopy to probe
the Dion–Jacobson (DJ) and Ruddlesden–Popper (RP) 2D
perovskite phases. We show the formation of charge transfer excitons
in DJ phases, resulting in a photoinduced Stark effect which is shown
to be dependent on the spacer size. By using electroabsorption spectroscopy,
we quantify the strength of the photoinduced electric field, while
temperature-dependent measurements demonstrate new features in the
transient spectra of RP phases at low temperatures resulting from
the quantum-confined Stark effect. This study reveals the impact of
spacer size and perovskite phase configuration on charge transfer
excitons in 2D perovskites of interest to their advanced material
design.
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