Intermediate-state imaging of electrical switching and quantum coupling of molybdenum disulfide monolayer

Rhenium diselenide (ReSe2) has gathered much attention due to its low symmetry of lattice structure, which makes it possess in-plane anisotropic optical, electrical as well as excitonic properties and further enables ReSe2 have an important application in optoelectronic devices. Here, we report the thickness-dependent exciton relaxation dynamics of mechanically exfoliated few-layer ReSe2 flakes by using time-resolved pump–probe transient transmission spectroscopies. The results reveal two thickness-dependent relaxation processes of the excitons. The fast one correlates with the exciton formation (i.e., the conversion of hot carriers to excitons), while the slow one is attributed to the exciton recombination dominated by defect-assisted exciton trapping besides photon emission channel. The decrease of scattering probability caused by defects leads to the increase of fast lifetime with thickness, and the increase of slow lifetime with thickness is related to the trap-mediated exciton depopulation induced by surface defects. Polarization-dependent transient spectroscopy indicates the isotropic exciton dynamics in the two-dimensional (2D) plane. These results are insightful for better understanding of excitonic dynamics of ReSe2 materials and its application in future optoelectronic and electronic devices.

Two-dimensional (2D) lead halide perovskite materials are solution-processable semiconductor materials, which would find promising applications in optoelectronic devices. The fundamental understanding of the structural phase transition in two-dimensional perovskites is of great importance for fully exploiting their potential applications in electronic and optoelectronic devices. Here, we report on how the external electric field affects the structural phase transition in 2D perovskite (BA)2PbI4 microplates via temperature-dependent photoluminescence spectroscopy. A high-temperature phase and a low-temperature phase can coexist in a wider range of temperatures. The external electric field would enhance the phase transition to the dominant phase depending on the surrounding temperature. This field-induced phase transition might be ascribed to the release of strain in the perovskite microplate induced by the applied electric field, leading to the change in the structural phase transition temperature. Our findings are of great significance not only to the fundamental understanding of phase transition but also to the design and optimization of two-dimensional perovskite based electronic and optoelectronic devices.

A tunable bandgap without doping is highly desirable for applications in optoelectronic devices. Herein, we develop a new method which can tune the bandgap without any doping. In the present research, the bandgap of Fe2O3 nanostructured films is simply tuned by changing the synthesis temperature. The Fe2O3 nanostructured films are synthesized on ITO/glass substrates at temperatures of 1100, 1150, 1200, and 1250 °C using the hot filament metal oxide vapor deposition (HFMOVD) and thermal oxidation techniques. The Fe2O3 nanostructured films contain two mixtures of Fe2+ and Fe3+ cations and two trigonal (α) and cubic (γ) phases. The increase of the Fe2+ cations and cubic (γ) phase with the elevated synthesis temperatures lifted the valence band edge, indicating a reduction in the bandgap. The linear bandgap reduction of 0.55 eV without any doping makes the Fe2O3 nanostructured films promising materials for applications in bandgap engineering, optoelectronic devices, and energy storage devices.

Histidine-based hybrid perovskites as promising materials for wide wavelength photodetection

Double perovskite-based optoelectronic devices are gaining attention due to their unique characteristics, including a simple and stable crystal structure. This study employs density functional theory (DFT) with the full-potential linearized augmented plane-wave (FP-LAPW) method to investigate the structural, electronic, optical, mechanical, and thermodynamic properties of A2BIrCl6 (A = Cs, Rb; B = Na, K) double perovskite halides. The primary aim is to assess their potential applicability in optoelectronic devices and renewable energy technologies. The cubic stability of the predicted compounds was confirmed through the Goldsmith tolerance factor, octahedral factor, and a new tolerance factor. Additionally, to confirm their thermodynamic stability, we assessed the formation energy, binding energy, and phonon dispersion curves. We used the TB-mBJ potential to accurately predict the optoelectronic properties. The calculations of the electronic band structure indicated that the examined double perovskites exhibit a direct band gap semiconducting nature, with the following band gap values: 1.927 eV for Cs2NaIrCl6 1.991 eV for Cs2KIrCl6, 2.025 eV for Rb2NaIrCl6, and 2.102 eV for Rb2KIrCl6. The A2BIrCl6 (A = Cs, Rb; B = Na, K) compounds demonstrate impressive optical properties, including low reflectivity and high light absorption coefficients (104 cm-1) in the visible spectrum. Their spectral response extends from the visible to the UV range, making them ideal candidates for applications in solar cells and optoelectronic devices. The mechanical stability of the titled compounds was confirmed through the Born-Huang stability conditions based on their stiffness constants. The brittle nature of all the examined perovskites is confirmed by Pugh's ratio, Cauchy pressure, and Poisson's ratio. Finally, the Helmholtz free energy (F), internal energy (E), entropy (S), and specific heat capacity (C v) are calculated based on the phonon density of states.

BACKGROUND: Monomers and polymers carrying pendent electro‐active fragments are widely studied due to their application in various optoelectronic devices. Monomers containing triphenylamino, triphenyldiamino and carbazol‐9‐yl fragments with vinyl, epoxy or acryl functional groups are mostly used. The synthesized materials are used for preparation of hole transport layers as well as host materials for electrophosphorescent light‐emitting diodes. Much fewer presentations are reported on the preparation of monomers containing other electro‐active or functional groups. RESULTS: Here we describe oxetane monomers and their oligomers containing various electro‐active pendent groups. The weight‐average molecular weights of the oligomers are in the range 1420–3250 g mol −1 with a molecular weight distribution of 1.7–4.1. The electron photoemission spectra of amorphous layers of the compounds established ionization potentials of 5.55–5.85 eV. Room temperature hole drift mobility in the layers of some oligomers exceeds 10 −7 cm 2 V −1 s −1 at high electric fields. CONCLUSION: The synthesized oligomers exhibit promising thermal and film‐forming properties. Amorphous layers of some of the materials demonstrate suitable ionization potentials and sufficient hole transport properties for their application in optoelectronic devices. Copyright © 2008 Society of Chemical Industry

Understanding charge carrier dynamics in two-dimensional (2D) semiconductors and their heterostructures is crucial for advancing their application in optoelectronic devices. In this work, two different 2D semiconductors, MoS2 and phenethylammonium lead iodide, (PEA)2PbI4 (a 2D perovskite), are physically coupled, and the excited-state dynamics are probed using femtosecond transient absorption measurements. Electron transfer from (PEA)2PbI4 to MoS2 and hole transfer from MoS2 to (PEA)2PbI4 were established by performing experiments at different excitation wavelengths (475 and 675 nm). The electron transfer step involved ultrafast hot-electron transfer (<1 ps) from (PEA)2PbI4 to MoS2, followed by thermalization. The electron and hole transfer between the 2D layers of the heterostructure was suppressed when a layer of poly(methyl methacrylate) (PMMA) was inserted between the two layers, thus breaking their interactions. The wavelength-dependent exciton and hot carrier dynamics in 2D heterostructures presented in this study have broad applications in energy conversion and optoelectronic devices.

Characterization of Ag-doped ZnO thin film for its potential applications in optoelectronic devices

Defect induced photoluminescence in MoS2 quantum dots and effect of Eu3+/Tb3+ co-doping towards efficient white light emission

Two-dimensional (2D) materials with high anisotropic properties, such as black phosphorus and ReS2, show amazing potential for applications in future nanoelectronic and optoelectronic devices. However, degradation of black phosphorus under ambient conditions and the expensiveness of Re block their application. In this study, another layered material, KP15, that has highly anisotropic properties was successfully prepared. The detailed crystal structure and electron-density distribution calculation reveal that KP15 exhibits an anisotropic layered structure with two rows of P tubes connected by K atoms that are antiparallel in a single layer. Outstanding chemical stability, angular dependence of the Raman response, excitation, and exciton emission at room temperature have been found in exfoliated KP15 nanoribbons. Importantly, the exciton emission at room temperature suggests the existence of a large exciton binding energy. Our results indicate that, because this layered material, KP15, has high anisotropic properties and ultrachemical stability and is derived from abundant raw materials, it has great potential for applications in optoelectronic devices.

Group IIIA phosphide nanocrystalline semiconductors are of great interest among the important inorganic materials because of their large direct band gaps and fundamental physical properties. Their physical properties are exploited for various potential applications in high-speed digital circuits, microwave and optoelectronic devices. Compared to II-VI and I-VII semiconductors, the IIIA phosphides have a high degree of covalent bonding, a less ionic character and larger exciton diameters. In the present review, the work done on synthesis of III-V indium phosphide (InP) nanowires (NWs) using vapour- and solution-phase approaches has been discussed. Doping and core-shell structure formation of InP NWs and their sensitization using higher band gap semiconductor quantum dots is also reported. In the later section of this review, InP NW-polymer hybrid material is highlighted in view of its application as photodiodes. Lastly, a summary and several different perspectives on the use of InP NWs are discussed.

Electronic structures and stability of double-walled armchair and zigzag AlN nanotubes

Enhancing red-light emission of CsPb(Br/I)3 quantum dots through noble metal nanostructure-mediated localized surface plasmon resonance

High aspect ratio copper nanowires and copper nanoparticles decorated by reduced graphene oxide for flexible transparent conductive electrodes

Optical properties of organic materials, specially a large family of π-conjugated to which polycarbonate belong, have been receiving lots of attention recently for potential applications in optoelectronics devices. The outstanding optical and electrical properties of these materials open a wide variety of applications in modern optoelectronic devices. Polycarbonate as the transparent layers in electroluminescence and photovoltaic cells have caused a great deal of interest due to their low cost and high chemical stability. In order to design optoelectronics devices more efficiently, the optical and electrical functions of each layer should be know.