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At least 91 records · Page 5

Multicolor Inks of Black Phosphorus for Midwave‐Infrared Optoelectronics

Abstract Black phosphorus (bP) based ink with a bulk bandgap of 0.33 eV ( λ = 3.7 µm) has recently been shown to be promising for large‐area, high performance mid‐wave infrared (MWIR) optoelectronics. However, the development of multicolor bP inks expanding across the MWIR wavelength range has been challenging. Here a multicolor ink process based on bP with spectral emission tuned from 0.28 eV ( λ = 4.4 µm) to 0.8 eV ( λ = 1.5 µm) is demonstrated. Specifically, through the reduction of bP particle size distribution (i.e., lateral dimension and thickness), the optical bandgap systematically blueshifts, reaching up to 0.8 eV. Conversely, alloying bP with arsenic (bP 1− x As x ) induces a redshift in the bandgap to 0.28 eV. The ink processed films are passivated with an infrared‐transparent epoxy for stable infrared emission in ambient air. Utilizing these multicolor bP‐based inks as an infrared light source, a gas sensing system is demonstrated that selectively detects gases, such as CO 2 and CH 4 whose absorption band varies around 4.3 and 3.3 µm, respectively. The presented ink formulation sets the stage for the advancement of multiplex MWIR optoelectronics, including spectrometers and spectral imaging using a low‐cost material processing platform.

Kim, Jae Ik↗

3D‐Mapping and Manipulation of Photocurrent in an Optoelectronic Diamond Device

Abstract Establishing connections between material impurities and charge transport properties in emerging electronic and quantum materials, such as wide‐bandgap semiconductors, demands new diagnostic methods tailored to these unique systems. Many such materials host optically‐active defect centers which offer a powerful in situ characterization system, but one that typically relies on the weak spin‐electric field coupling to measure electronic phenomena. In this work, charge‐state sensitive optical microscopy is combined with photoelectric detection of an array of nitrogen‐vacancy (NV) centers to directly image the flow of charge carriers inside a diamond optoelectronic device, in 3D and with temporal resolution. Optical control is used to change the charge state of background impurities inside the diamond on‐demand, resulting in drastically different current flow such as filamentary channels nucleating from specific, defective regions of the device. Conducting channels that control carrier flow, key steps toward optically reconfigurable, wide‐bandgap optoelectronics are then engineered using light. This work might be extended to probe other wide‐bandgap semiconductors (SiC, GaN) relevant to present and emerging electronic and quantum technologies.

Wood, Alexander A.↗

Ordered and Patterned Assembly of Organic Micro/Nanocrystals for Flexible Electronic and Optoelectronic Devices

Organic semiconductor micro/nanocrystals (OSMCs) have attracted intensive research over the past few decades. Their unique electrical and mechanical properties afford them applications in a vast network of active flexible electronic and optoelectronic fields, such as organic field‐effect transistors (OFETs), photodetectors (PDs), and organic light‐emitting diodes (OLEDs) etc. However, the growth orientation and location of OSMCs are usually stochastic in nature, which hinders the further use of OSMCs in large‐area plastic electronic devices. On the other hand, traditional microelectronic processing techniques like photolithography may damage the plastic substrates, polymer insulators, and organic materials. Thus the alignment and patterning of OSMCs and development of new device construction technologies are prerequisite for their flexible device applications in practice. In this progress report,the important advancement for fabricating the aligned and patterned OSMCs, with a focus on their applications in next‐generation flexible electronic and optoelectronic devices, is highlighted. Also, the challenges and outlooks of the ordered and patterned OSMCs in the flexible device applications are presented.

Deng, Wei↗

1D SbSeI, SbSI, and SbSBr With High Stability and Novel Properties for Microelectronic, Optoelectronic, and Thermoelectric Applications

Mechanical exfoliation of 2D materials has triggered an explosive interest in lowdimensional material research. We extend this idea to 1D van derWaals materials. Three 1D semiconductors (SbSeI, SbSI and SbSBr) with high stability and novel electronic properties are discovered using first principles calculations. Both the dynamical and the thermal stability of these 1D materials are examined. We demonstrate that their nanowire thinner than 7 Å can be easily obtained by mechanical exfoliation, hydrothermal method or sonochemical method. The bulk-to-1D transition results in dramatic changes in band gap, effective mass and static dielectric constant due to quantum confinement, making 1D SbSeI a highly promising channel material for transistors with gate length shorter than 1 nm. Under small uniaxial strain, these materials are transformed from indirect into direct band gap semiconductors, paving the way for optoelectronic devices and mechanical sensors. Moreover, the thermoelectric performance of these materials is significantly improved over their bulk counterparts. These highly desirable properties render SbSeI, SbSI and SbSBr promising 1D materials for applications in future microelectronics, optoelectronics, mechanical sensors, and thermoelectrics.

36 MATERIALS SCIENCE↗

Optically Induced Static Magnetization in Metal Halide Perovskite for Spin‐Related Optoelectronics

Abstract Understanding the feasibility to couple semiconducting and magnetic properties in metal halide perovskites through interface design opens new opportunities for creating the next generation spin‐related optoelectronics. In this work, a fundamentally new phenomenon of optically induced magnetization achieved by coupling photoexcited orbital magnetic dipoles with magnetic spins at perovskite/ferromagnetic interface is discovered. The depth‐sensitive polarized neutron reflectometry combined with in situ photoexcitation setup, constitutes key evidence of this novel effect. It is demonstrated that a circularly polarized photoexcitation induces a stable magnetization signal within the depth up to 7.5 nm into the surface of high‐quality perovskite (MAPbBr 3 ) film underneath a ferromagnetic cobalt layer at room temperature. In contrast, a linearly polarized light does not induce any detectable magnetization in the MAPbBr 3 . The observation reveals that photoexcited orbital magnetic dipoles at the surface of perovskite are coupled with the spins of the ferromagnetic atoms at the interface, leading to an optically induced magnetization within the perovskite’s surface. The finding demonstrates that perovskite semiconductor can be bridged with magnetism through optically controllable method at room temperature in this heterojunction design. This provides the new concept of utilizing spin and orbital degrees of freedom in new‐generation spin‐related optoelectronic devices.

36 MATERIALS SCIENCE↗

Oriented gold nanorod arrays: self-assembly and optoelectronic applications

We present that self-assembly of anisotropic plasmonic nanomaterials into ordered superstructures has become popular in nanoscience because of their unique anisotropic optical and electronic properties. Gold nanorods (GNRs) are a well-defined functional building block for fabrication of these superstructures. They possess important anisotropic plasmonic characteristics that are resulted from strong local electric field and responsive to visible and near infrared light, which attracts extensive attention in various fields, such as biomedical technologies, plasmon-enhanced spectroscopies, and optoelectronic devices. There are recent examples of assembling the GNRs into ordered arrays or superstructures through processes such as solvent evaporation, interfacial assembly. In this review, we describe recent progresses in the development of the self-assembled GNR arrays with focus on the formation of oriented GNR arrays on substrates. We discuss key driving forces such as van der Waals (vdW), electrostatic interactions, steric force, and depletion force. We survey different strategies and self-assembly processes of forming oriented GNR arrays. Lastly, we also overview the applications of the oriented GNR arrays in optoelectronic devices especially surface enhanced Raman scattering (SERS). At the end of this review, we briefly summarize the review and discuss future challenges and perspectives.

36 MATERIALS SCIENCE↗

Electron-Deficient Phenazines: Synthesis, Structures, Redox, and Optoelectronic Properties in the Gas Phase, in Solution, and in the Solid State

High-temperature gas-phase reactions of 1,4-C4F8I2 with phenazine (PHNZ) afforded new thermally- and air-stable derivatives with cyclo-C4F8 substituents, viz. 1,2-PHNZ(C4F8), 2,3-PHNZ(C4F8), 1,2:6,7-PHNZ(C4F8)2, 1,2:7,8-PHNZ(C4F8)2, and 1,2:8,9-PHNZ(C4F8)2. Reactions in the presence of Cu powder resulted in reductive-defluorination/aromatization of some of the cyclo-C4F8 substituents to produce 2,3-PHNZ(C4F4), 2,3-PHNZ(C4HF3), and 1,2:6,7-PHNZ(C4F8)(C4F4), which are formally tri- or tetrafluoro derivatives of benzo[a]phenazine. Single-crystal X-ray diffraction structures of these compounds demonstrate the planarity of 2,3-PHNZ(C4F4) and 2,3-PHNZ(C4HF3) and ordered p-stacking in 1,2-PHNZ(C4HF3), 1,2-PHNZ(C4F4), 1,2-PHNZ(C4F8), and 2,3-PHNZ(C4F8). Low-temperature gas-phase photoelectron spectra of the PHNZ(C4F8)1,2 compounds show that they are strong electron acceptors, with the three PHNZ(C4F8)2 isomers having electron affinities exceeding that of C60. Cyclic voltammetry in acetonitrile show that the five PHNZ(C4F8)1,2 compounds exhibit reversible one-electron reductions with large positive shifts in their reduction potentials relative to unsubstituted PHNZ. Spectroelectrochemical absorption and EPR spectra of PHNZ(C4F8)1,2- • anion radicals and extensive DFT calculations revealed the significant role that the different substitution patterns have on determining the optoelectronic properties of the PHNZ(C4F8)1,2 derivatives and PHNZ(C4F8)1,2- • anion radicals. Time-resolved microwave conductivity measurements and photoluminescence spectra of blends of the PHNZ(C4F8)1,2 derivatives with the donor poly(3-hexylthiophene) (P3HT) were recorded to assess the possible use of the new compounds in optoelectronic devices.

Balser, Sebastian↗

Magnetic, Optoelectronic, and Thermodynamic Properties of Sr{sub 2}CrXO{sub 6} (X = La and Y): Half-Metallic and Ferromagnetic Behavior

The effects of spin polarization on the structure, magnetic, and optoelectronic properties of Cr-based series of double perovskites Sr{sub 2}CrXO{sub 6} (X = La and Y) have been studied by using the full-potential linearized augmented plane-wave method (FP-LAPW), based on the density functional theory (DFT) as implemented in the Wien2k code, within the generalized gradient approximation (GGA), GGA + U, and GGA plus Trans-Blaha-modified Becke–Johnson (TB-mBJ) as the exchange correlation. Our results show a similar half-metallic ferromagnetic ground state for both materials. From the electronic properties, it is found that Sr{sub 2}CrYO{sub 6} has a direct band gap at (Γ-Γ) direction and Sr{sub 2}CrLaO{sub 6} has an indirect band gap at (Γ-W) direction. Furthermore, we have computed the optic and thermodynamic properties which are investigated for the first time. Consequently, the magnetic, optoelectronic, and thermodynamic properties show these compounds are promising for high technological applications, namely spintronic materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Study of phase-locking of optoelectronic microwave oscillators considering amplitude perturbation

This paper presents a detailed study of the phase-locking phenomenon in single-loop optoelectronic microwave oscillators considering strong radio frequency (RF) signal injection. The analyses are made in terms of the lock-range, beat frequency and the spectral components of the unlocked-driven oscillator in presence of amplitude perturbation. An approximate expression for the amplitude perturbation of the oscillator is derived and the influence of amplitude perturbation on the phase-locking dynamics is analysed. The influence of external RF signal on the frequency pulling of the unlocked-driven optoelectronic oscillator (OEO) is also studied. It is shown that the unlocked-driven OEO output signal has a very non-symmetrical sideband distribution about the carrier. Also, analytical technique for studying the response characteristics of a phase-locked OEO to pure continuous wave amplitude modulated signal is presented. The simulation findings are also given in partial support of the conclusions of the analysis.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Optoelectronic properties of germanium iodide perovskites AGeI{sub 3} (A = K, Rb and Cs): first principles investigations

In this paper, we have investigated the structural, optoelectronic and elastic properties of AGeI{sub 3} (A = K, Rb and Cs) using the density functional theory with generalized gradient approximation (GGA) for potential exchange correlation. The modified Becke–Johnson (mBJ-GGA) potential approximation is also used for calculating the optoelectronic properties of the material. The results show that the band structure of the perovskites AGeI{sub 3} (have a semiconductor behavior with direct band gap at R–R direction, the gap energy values calculated with mBJ-GGA, for each compound as following: 0.58, 0.63, and 0.71 eV, respectively. The optical properties, such as real and imaginary parts of the dielectric functions, refractive index, reflectivity, conductivity and absorption coefficient are investigated. As results, these compounds are competent candidates photovoltaic application like light harvester.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Effect of HfO{sub 2} on the dielectric, optoelectronic and energy harvesting properties of PVDF

In this article, energy recovery based on PVDF doped with HfO{sub 2} is proposed. The free energy of CH{sub 2}=CF{sub 2} is determined in different base with the B3LPY functional. The basis set LanL2DZ was chosen because it takes into account the atom of hafnium of atomic number Z=72 which exceeds the extension of some basis sets. In addition, LanL2DZ gives an accurate result and a reasonable computing time. The geometries of the molecules were optimized with B3LPY/LanL2DZ. The motivation of this study is the improvement of the optoelectronic, dielectric and piezoelectric properties of PVDF by introducing HfO{sub 2} into its matrix. We determined the parameters of (−CH{sub 2}−CF{sub 2}−){sub 3}⋅xHfO{sub 2} and identified the effect of HfO{sub 2} on the PVDF. It appears that the permittivity of the modified PVDF increases. When the PVDF is doped once or twice, a fluorine atom is captured by the hafnium. The migration of fluorine towards HfO{sub 2} considerably favors the electric polarization of the molecule. It then results in an important dipole moment with a polar phase undoubtedly favored. Our results show that the molecule (−CH{sub 2}−CF{sub 2}−){sub 3}⋅HfO{sub 2} is a good dielectric material (E{sub g}=5.90 eV) and can be a good piezoelectric material. The electronic affinity of the modified PVDF is significantly higher than that of virgin PVDF. This demonstrates that HfO{sub 2}-doped PVDF is more stable than virgin PVDF. The piezoelectric properties are significantly improved. The piezoelectric coefficient varies between 13.111 and 25.635 pC N{sup −1} for the modified PVDF compared to 11.979 pC N {sup −1} for the virgin PVDF. In conclusion, HfO{sub 2} improves the dielectric, optoelectronic and piezoelectric properties of PVDF.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Enhanced optoelectronic and elastic responses in fluorinated penta-BCN

We report surface passivation in two-dimensional (2D) materials is one of the best approaches to modulate the structural, dynamical, and mechanical stabilities thereby enhancing chemical and physical properties for optoelectronic applications. Here, we report an ab-initio investigation on structurally, thermally, dynamically, and mechanically stable, and experimentally feasible fluorinated penta-BCN (F-BCN) monolayer. The structural reconstruction after fluorination, increases bond lengths and thickness to reduce the average stiffness and elasticity attaining the mechanical isotropy. Nevertheless, the value of 2D Young’s modulus of F-BCN is comparable to the pristine structure at 6% of compression without mechanical instability. A significant bandgap tailoring is achieved, similar to that of mechanical sensitivity, due to applied strain. Remarkably, following the fluorine passivation, the monolayer’s induced wide direct bandgap semiconducting behavior improves optical absorbance and reflectivity, decreases energy loss, changes optical anisotropy, and makes it a promising candidate material for optoelectronic and nanomechanical applications.

36 MATERIALS SCIENCE↗

Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta{sub 3}N{sub 5}

Presented herein is a detailed discussion of the properties of the lattice dynamic and optoelectronic properties of tantalum(V) oxynitride (TaON) and tantalum(V) nitride (Ta{sub 3}N{sub 5}), from experimental and theoretical standpoint. The active Raman and infra red (IR) frequencies of TaON and Ta{sub 3}N{sub 5} were measured using confocal Raman and Fourier Transform Infrared spectroscopies (FTIR) and calculated using the linear response method within the density functional perturbation theory (DFPT). The detailed study leads to an exhaustive description of the spectra, including the symmetry of the vibrational modes. Electronic structures of these materials were computed using DFT within the range-separated hybrid HSE06 exchange–correlation formalism. Electronic and ionic contributions to the dielectric constant tensors of these materials were obtained from DFPT within the linear response method using the PBE functional. Furthermore, effective mass of photogenerated holes and electrons at the band edges of these compounds were computed from the electronic band structure obtained at the DFT/HSE06 level of theory. The results suggest that anisotropic nature in TaON and Ta{sub 3}N{sub 5} is present in terms of dielectric constant and effective masses. - Graphical abstract: Detailed investigation has been conducted from combined experimental and theoretical approaches on Raman and IR spectroscopies, electronic structures, dielectric constants and effective masses of TaON and Ta{sub 3}N{sub 5}. - Highlights: • Crystal structures of TaON and Ta{sub 3}N{sub 5} are discussed based on XRD and DFT calculation. • Raman and IR spectra of TaON and Ta{sub 3}N{sub 5} materials are measured and computed by DFPT method. • Optoelectronic properties of TaON and Ta{sub 3}N{sub 5} are discussed. • Dielectric constant and effective masses of TaON and Ta{sub 3}N{sub 5} are calculated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Realization of BaZrS 3 chalcogenide perovskite thin films for optoelectronics

BaZrS 3 is a prototypical chalcogenide perovskite, an emerging class of unconventional semiconductor. Recent results on powder samples reveal that it is a material with a direct band gap of 1.7–1.8 eV, a very strong light-matter interaction, and a high chemical stability. Due to the lack of quality thin films, however, many fundamental properties of chalcogenide perovskites remain unknown, hindering their applications in optoelectronics. In this work, we report the fabrication of BaZrS 3 thin films, by sulfurization of oxide films deposited by pulsed laser deposition. We show that these films are n-type with carrier densities in the range of 10 19 -10 20 cm -3 . Depending on the processing temperature, the Hall mobility ranges from 2.1 to 13.7 cm 2 /Vs. The absorption coefficient is > 10 5 cm -1 at photon energy >1.97 eV. Temperature dependent conductivity measurements suggest shallow donor levels. By assuring that BaZrS 3 is a promising candidate, these results potentially unleash the family of chalcogenide perovskites for optoelectronics such as photodetectors, photovoltaics, and light emitting diodes.

36 MATERIALS SCIENCE↗

Colloidal Synthesis of Single-Layer Quasi-Ruddlesden–Popper Phase Bismuth-Based Two-Dimensional Perovskite Nanosheets with Controllable Optoelectronic Properties

Single- and few-layered two-dimensional (2D) nanomaterials have attracted intense research interest in the last two decades due to their unique electronic and optoelectronic properties leading to various potential applications. Herein, we report the colloidal synthesis of Bi-based 2D perovskite nanosheets (PEG6-NH 3 +) n Cs 3-n Bi 2 X 9 , where X = CI, Br, and I, through careful design of reaction conditions and selection of poly(ethylene glycol) (PEG6) surface passivating ligands. The 2D nanosheets are similar to 5 nm in thickness with micron-sized lateral dimensions and display composition-dependent band gap and work function modulation. Furthermore, small-angle X-ray scattering analysis substantiates that the individual inorganic crystal layer, Cs 3-n Bi 2 X 9 , is separated by the spacer, PEG6 ligand. Additionally, we determined that PEG6-NH 2 is an essential passivating ligand and spacer for the formation of Bi-based 2D nanosheets. Most importantly, controlled crystallization of the colloidal dispersion of nanosheets results in the formation of superlattice microstructures of the quasi-Ruddlesden-Popper phase. These microstructures can be exfoliated to ultrathin nanosheets by overcoming the van der Waals interaction between the organic passivating layers. The controlled synthesis of lead-free 2D perovskite nanosheets presented here can expand their utility to photocatalytic and optoelectronic applications with reduced toxicity.

36 MATERIALS SCIENCE↗

Applicability of Allen–Heine–Cardona Theory on MO x Metal Oxides and ABO 3 Perovskites: Toward High-Temperature Optoelectronic Applications [plus supplemental information]

We report characterizing the temperature-dependent electronic structures of optoelectronic materials is vital for their application in high-temperature processes. Allen–Heine–Cardona (AHC) theory is an established theory to determine the impact of electron–phonon coupling on the temperature renormalization of the electronic structure. A question of fundamental interest is how applicable this approach can be in a broad range of materials. Herein, we establish the consensus on the temperature dependence of band gaps between AHC predictions and experimental measurements, in a versatile set of nine MO x metal oxides and six ABO 3 perovskites that are utilized as gas sensors. Both calculations and measurements point to the appreciable band gap downshifts within the temperature range relevant to typical high-temperature applications in all examined materials. The correlation between the band gaps and temperatures was quantified at zero- and finite-temperature limits using the analytical parameters of the O’Donnell model. We found fairly comparative agreements between AHC- and experiment-derived parameters, especially for the parameters (S and $\langle\hbar$ω$\rangle$) defining the temperature dependence behavior of band gaps at the finite-temperature regime. Our findings provide important implications for the first-principles modeling of the electronic structures and their temperature dependency, which should be the focus toward high-temperature optoelectronic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

First-Principles Discovery of Novel LiInP 2 S 6 Polymorphs with Promising Optoelectronic Responses

Recent advances in two-dimensional (2D) van der Waals (vdW) metal thiophosphates have attracted considerable attention due to their promising ionic conductivity, optical characteristics, and tunable physical properties. Within this material family, LiInP 2 S 6 has emerged as an intriguing candidate, not only because of its sensitivity to air and moisture but also due to its suitable band gap within the UV−vis range, enabling potential optoelectronic and photocatalytic applications. In this study, through comprehensive first-principles investigations, we unveil two previously unreported polymorphs of LiInP 2 S 6 in the monoclinic C2/c and trigonal P3̅1c (in-gap) space groups, in addition to examining the experimentally synthesized P3̅1c (in-layer) phase. Our studies identify the C2/c structure as the ground state, lying 9 meV per unit cell lower in energy than the experimentally realized trigonal P3̅1c (in-layer) phase. Further, we systematically examine the elastic, mechanical, thermodynamical, dynamical, electronic, and optical properties of all three polymorphs, confirming their mechanical, thermal, and dynamical stability. Notably, the P3̅1c (in-gap) phase exhibits enhanced stiffness, while the calculated indirect band gaps and strong photon absorption in the UV−vis range (∼3 eV) highlight the potential of the studied LiInP 2 S 6 phases for iontronic devices and optoelectronic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Oxidation-Induced Polymerization of InP Surface and Implications for Optoelectronic Applications

InP is among the most studied materials for energy-conversion applications including optoelectronics and photoelectrochemical devices. One of the long-standing challenges with this material, and III–V semiconductors more generally, is to understand and control surface oxide formation, which critically impacts device functionality, performance, and durability. In this work, we integrate advanced in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) and ab initio simulations to reveal the mechanism of the oxidation process on the InP(001) surface. By interpreting the APXPS results through direct ab initio spectroscopic calculations of surface models, and by comparing calculated and measured work functions, we provide an unbiased picture of the chemical evolution of the thermal oxide. Furthermore, at low temperatures (<573 K), O 2 exposure leads to predominant formation of cross-linked PO x units dispersed with submonolayer thickness, which grow into an amorphous two-dimensional (2D) film that is kinetically limited to the surface layer. Increased temperature (>573 K) leads to the polymerization of PO x units and the formation of a complex, inhomogeneous 3D network of surface oxide that is progressively indium rich and phosphorus poor toward the surface. Finally, accelerated phosphorus loss via a hitherto unreported coupled charge-transfer isomer transformation mechanism leads to the formation of a thick, amorphous In 2 O 3 -like oxide at 773 K with very different optoelectronic and hot carrier transportation properties. In addition to unraveling complex mechanisms of surface oxidation, our results suggest the possibility of deliberately tuning oxide composition by leveraging competition between thermodynamic and kinetic factors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗