136 research outputs found
Feature issue introduction: halide perovskites for optoelectronics
This joint Optics Express and Optical Materials Express feature issue presents a collection of nine papers on the topic of halide perovskites for optoelectronics. Perovskite materials have attracted significant attention over the past four years, initially for their outstanding performance in thin film solar cells, but more recently for applications in light-emitting devices (LEDs and lasers), photodetectors and nonlinear optics. At the same time, there is still much more to learn about the fundamental properties of these materials, and how these depend on composition, processing, and exposure to the environment. This feature issue provides a snapshot of some of the latest research in this rapidly-evolving multidisciplinary field
Feature issue introduction: halide perovskites for optoelectronics
This joint Optics Express and Optical Materials Express feature issue presents a collection of nine papers on the topic of halide perovskites for optoelectronics. Perovskite materials have attracted significant attention over the past four years, initially for their outstanding performance in thin film solar cells, but more recently for applications in lightemitting devices (LEDs and lasers), photodetectors and nonlinear optics. At the same time, there is still much more to learn about the fundamental properties of these materials, and how these depend on composition, processing, and exposure to the environment. This feature issue provides a snapshot of some of the latest research in this rapidly-evolving multidisciplinary field
Chirality dependence of the absorption cross-section of carbon nanotubes
The variation of the optical absorption of carbon nanotubes with their
geometry has been a long standing question at the heart of both metrological
and applicative issues, in particular because optical spectroscopy is one of
the primary tools for the assessment of the chiral species abundance of
samples. Here, we tackle the chirality dependence of the optical absorption
with an original method involving ultra-efficient energy transfer in
porphyrin/nanotube compounds that allows uniform photo-excitation of all chiral
species. We measure the absolute absorption cross-section of a wide range of
semiconducting nanotubes at their S22 transition and show that it varies by up
to a factor of 2.2 with the chiral angle, with type I nanotubes showing a
larger absorption. In contrast, the luminescence quantum yield remains almost
constant
Solid-State Physics Perspective on Hybrid Perovskite Semiconductors
International audienceIn this review we examine recent theoretical investigations on 2D and 3D hybrid perovskites (HOP) that combine classical solid-state physics concepts and density functional theory (DFT) simulations as a tool for studying their optoelectronic properties. Such an approach allows one to define a new class of semiconductors, where the pseudocubic high temperature perovskite structure plays a central role. Bloch states and k.p Hamiltonians yield new insight into the influence of lattice distortions, including loss of inversion symmetry, as well as spin-orbit coupling. Electronic band folding and degeneracy, effective masses and optical absorption are analyzed. Concepts of Bloch and envelope functions, as well as confinement potential are discussed in the context of layered HOP and 3D HOP heterostructures. Screening and dielectric confinements are important for room temperature optical properties of 3D and layered HOP, respectively. Non-radiative Auger effects are analyzed for the first time close to the electronic band gap of 3D hybrid perovskites
Vibrational properties of 2H-PbI2 semiconductors studied via Density Functional Theory calculations
International audienceDensity Functional Theory is used to study the vibrational properties of 2H-PbI2 semiconductor. The Born charge tensors are determined. Calculated phonon frequencies at the Brillouin zone center are compared to Raman scattering and IR absorption measurements. The computed Raman spectra show a good agreement with available experimental data. The simulated phonon dispersion curves are compared with triple-axis neutron scattering measurements
Quantum efficiency of energy transfer in noncovalent carbon nanotube/porphyrin compounds
International audienceWe report on the quantum yield of excitation energy transfer in non-covalently bound nan- otube/porphyrin compounds. Evidence for energy transfer is gained from photoluminescence exci- tation experiments. We perform a quantitative evaluation of the transfer quantum yield in the case of (6,5) nanotubes through three independent methods : quantitative PLE measurements, evalu- ation of the luminescence quenching of the donor (porphyrin) and ultrafast transient absorption measurements. The latter shows a tremendous increase of the porphyrin recovery rate upon incor- poration in the compound. All these measurements consistently lead to an exceptional quantum yield efficiency
Taming Friedrich-Wintgen interference in resonant metasurface: vortex laser emitting at on-demand tilted-angle
Friedrich-Wintgen (FW) interference is an atypical coupling mechanism that
grants loss exchange between leaky resonances in non-Hermitian classical and
quantum systems. Intriguingly, such an mechanism makes it possible for
destructive interference scenario in which a radiating wave becomes a bound
state in the continuum (BIC) by giving away all of its losses. Here we propose
and demonstrate experimentally an original concept to tailor FW-BICs as
polarization singularity at on-demand wavevectors in optical metasurface. As a
proof-of-concept, using hybrid organic-inorganic halide perovskite as active
material, we empower this novel polarization singularity to obtain lasing
emission exhibiting both highly directional emission at oblique angles and
polarization vortex in momentum space. Our results pave the way to steerable
coherent emission with tailored polarization pattern for applications in
optical communication/manipulation in free-space, high-resolution imaging
/focusing and data storage
Multinuclear NMR as a tool for studying local order and dynamics in CH3NH3PbX3 (X = Cl, Br, I) hybrid perovskites
International audienceWe report on Pb, Br, N, H, C and H NMR experiments for studying the local order and dynamics in hybrid perovskite lattices. Pb NMR experiments conducted at room temperature on a series of MAPbX compounds (MA = CHNH; X = Cl, Br and I) showed that the isotropic Pb NMR shift is strongly dependent on the nature of the halogen ions. Therefore Pb NMR appears to be a very promising tool for the characterisation of local order in mixed halogen hybrid perovskites. Pb NMR on MAPbBrI served as a proof of concept. Proton, C and N NMR experiments confirmed the results previously reported in the literature. Low temperature deuterium NMR measurements, down to 25 K, were carried out to investigate the structural phase transitions of MAPbBr. Spectral lineshapes allow following the successive phase transitions of MAPbBr. Finally, quadrupolar NMR lineshapes recorded in the orthorhombic phase were compared with simulated spectra, using DFT calculated electric field gradients (EFG). Computed data do not take into account any temperature effect. Thus, the discrepancy between the calculated and experimental EFG evidences the fact that MA cations are still subject to significant dynamics, even at 25 K
Pi-stacking functionalization through micelles swelling: Application to the synthesis of single wall carbon nanotube/porphyrin complexes for energy transfer
We report on a new, orginal and efficient method for "pi-stacking"
functionalization of single wall carbon nanotubes. This method is applied to
the synthesis of a high-yield light-harvesting system combining single wall
carbon nanotubes and porphyrin molecules. We developed a micelle swelling
technique that leads to controlled and stable complexes presenting an efficient
energy transfer. We demonstrate the key role of the organic solvent in the
functionalization mechanism. By swelling the micelles, the solvent helps the
non water soluble porphyrins to reach the micelle core and allows a strong
enhancement of the interaction between porphyrins and nanotubes. This technique
opens new avenues for the functionalization of carbon nanostructures.Comment: 6 pages, 5 figure
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