Optoelectronic Applications Research Articles

Strain‐Engineered Level Alignment in the MoTe2/WSe2 Heterobilayer

When stacked into heterostructures, layered transition metal dichalcogenides (TMDCs) exhibit peculiar electronic and optical properties that may differ substantially from those of their constituents and that largely depend on the level alignment. For example, the MoTe2/WSe2 heterobilayer exhibits a type I band lineup, which can be exploited in emitting devices but limits charge separation. In this first‐principle study based on density functional theory and many‐body perturbation theory, strain is proposed as an effective means to make MoTe2/WSe2 a type II heterostructure. By exploring several configurations where biaxial strain is applied to either or both monolayers, the top of the valence band and the bottom of the conduction band are found at different points in k‐space leading to an indirect‐to‐direct bandgap transition when the lattice constant of WSe2 is expanded by 3.2% or more. In terms of optical properties, all considered systems exhibit a first dark excitation, consistently shifting in energy with the direct electronic gap, while the absorption onset does not vary significantly with strain. Our findings suggest strain as a powerful tool for fine tuning the electronic and optical properties of TMDC heterostructures while preserving their fundamental characteristics, thus opening new avenues for designing optoelectronic applications.

Dark Current Suppression in Two‐dimensional Histamine Lead Iodine Perovskite Single Crystal for X‐ray Detection and Imaging

AbstractLead halide perovskites have emerged as attractive X‐ray detector materials, owing to properties such as strong X‐ray stopping power, excellent carrier transport, and high sensitivity. Additionally, they can be easily prepared by using solution‐based synthesis approaches. However, traditional 3D (three‐dimensional) perovskites X‐ray detectors have shown limited application due to high dark currents generated under bias voltage as a result of strong ion migration. In this work, an X‐ray detector with a vertical structure device is demonstrated using 2D (two‐dimensional) histamine lead halide perovskite single crystal HAPbI4 (HPI, HA = histamine). Due to the dielectric screening effect of diamine and the vertical structure of the HPI device, the fabricated detector shows a sensitivity of 7737 µC Gyair−1 cm−2 under a bias voltage of 30 V. Furthermore, the detector shows a sensitivity of 293 µC Gyair−1 cm−2 and detection limit of 51.38 nGyair s−1 without bias voltage, wherein the dark current is almost completely suppressed. All of these properties indicate the X‐ray detection device is a promising candidate for next‐generation optoelectronic applications.

Nanostructured AlxIn1−xPySbzAs1−y–z semiconductor alloy as a competent material for optoelectronic and solar cell applications

Nanostructured AlxIn1−xPySbzAs1−y–z semiconductor alloy as a competent material for optoelectronic and solar cell applications

Insights on bio-medical, quantum, and optoelectronic applications of 2D transition metal dichalcogenides–a review

Insights on bio-medical, quantum, and optoelectronic applications of 2D transition metal dichalcogenides–a review

Complex‐mediated nucleophilic aromatic substitution with aryl nitriles to realize intramolecular flapping‐restricted D‐A AIEgens for bioimaging

AbstractDonor‐acceptor (D‐A) compounds are particularly important in optoelectronic and biological applications. However, they are normally synthesized in the presence of transition metal catalysts. Herein, we report a metal‐free method by a complex‐mediated nucleophilic aromatic substitution of aryl nitriles with amines. The method can lead to rich D‐A type aggregation‐induced emission luminogens (AIEgens) with tunable properties. They emit from deep‐blue to yellow‐green and possess high photoluminescence quantum yields up to 70.5% in the aggregate state. Interestingly, the suppression of intramolecular flapping is proved to play an indispensable role in the AIE behavior, which is different from the mechanism met in other AIEgens. Moreover, the biocompatible AIEgens possess specific staining of lipid droplets in HeLa cells and the superiority of identifying fatty liver over traditional Oil Red O staining is exhibited.

Controllable p-type doping and improved conductance of few-layer WSe2 via Lewis acid

Manipulation of the electronic properties of layered transition-metal dichalcogenides (TMDs) is of fundamental significance for a wide range of electronic and optoelectronic applications. Surface charge transfer doping is considered to be a powerful technique to regulate the carrier density of TMDs. Herein, the controllable p-type surface modification of few-layer WSe2by FeCl3Lewis acid with different doping concentrations have been achieved. Effective hole doping of WSe2has been demonstrated using Raman spectra and XPS. Transport properties indicated the p-type FeCl3surface functionalization significantly increased the hole concentration with 1.2 × 1013cm-2, resulting in 6 orders of magnitude improvement for the conductance of FeCl3-modified WSe2compared with pristine WSe2. This work provides a promising approach and facilitate the further advancement of TMDs in electronic and optoelectronic applications.

On the Functionalization of C60 with Vinylallenes Generated in situ by Rhodium Catalysis

AbstractThe functionalization of fullerenes is important for several reasons, primarily related to enhancing their chemical reactivity, solubility, and potential of applications in optoelectronics and biomedicine. In this study, we present a novel approach to functionalize C60 through a cascade process encompassing an unprecedented Rh‐catalyzed cycloisomerization of 1,6‐allenynes to in situ generate a vinylallene that is followed by a Diels‐Alder reaction with pristine fullerene, resulting in the formation of 6,6‐fused bicyclic fullerene derivatives. The mechanism governing this process was elucidated by DFT calculations and confirmed by deuterium labelling and control experiments, demonstrating the critical role of traces of water in the reaction medium to mediate the observed reactivity.

First-Principles Investigation of Structural, Electronic, Optical, Elastic, and Thermoelectric Properties of Cubic Francifluorite Perovskites FrXF3 (X = Si, Ge, and Sn) for Optoelectronic and Thermoelectric Device Applications

Abstract This study presents the results of first-principles calculations based on Density Functional Theory (DFT) implemented in the Wien2k code, investigating the properties of FrXF3 compounds where B represents Si, Ge, and Sn. Various exchange-correlation functionals, including Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof (GGA-PBE), Perdew-Burke-Ernzerhof revised for Solids (GGA-PBEsol), Wu-Cohen exchange (GGA-WC), and Modified Becke-Johnson potential (TB-mBJ), were employed to comprehensively analyze the structural, electronic, optical, elastic, and thermoelectric characteristics of these compounds. The analysis of band structures and density of states revealed that all three compounds exhibit semiconducting behavior with direct band gaps, and the band gaps decrease as we move from Si to Sn. The calculated optical properties indicate strong optical responses in the visible to ultraviolet energy range, suggesting potential applications in optoelectronics. Furthermore, the study evaluated the thermoelectric parameters, including thermal and electrical conductivity, power factor, Seebeck coefficient, and figure of merit. The results demonstrate that the FrXF3 compounds possess remarkable thermoelectric potential, indicating their suitability for thermoelectric applications. Overall, this comprehensive investigation provides valuable insights into the structural, electronic, optical, elastic, and thermoelectric properties of FrXF3 compounds, highlighting their potential for various technological applications, particularly in the field of optoelectronics and thermoelectric devices.

Twenty Years of Graphene: From Pristine to Chemically Engineered Nano-Sized Flakes.

It is a celebratory moment for graphene! This year marks the 20th anniversary of the discovery of this amazing material by Geim and Novoselov. Curiously, it coincides with the century mark of graphite's layered structure discovery. Since the discovery of graphene with the promise that its outstanding properties would change the world, society often wonders where is graphene? In this context, their discoverers said in 2005, "despite the reigning optimism about graphene-based electronics, "graphenium" microprocessors are unlikely to appear for the next 20 years". Today, possibilities for graphene are endless! It can be used in electronics, photonics, fuel cells, energy storage, artificial intelligence, biomedicine, and even cultural heritage or sports. Additionally, the electronic properties of this material have been modified in fascinating ways. Bilayer graphene sheets have been found to be superconductive when twisted at a "magic angle", leading to a new and exciting field of research known as "moiré quantum materials" or "twistronics". Additionally, small graphene fragments with nanometer sizes undergo a quantum confinement effect of electrons, affording semiconductive materials with applications in optoelectronics. Organic synthesis allows the preparation of molecules with a graphene-like pattern with total control of the shape and size, exhibiting a big catalog of chiroptical and optoelectronic properties. This Perspective shows some of the fascinating milestones raised in the field of graphene-like materials from a chemical point of view, including functionalization strategies employed to chemically modify the topology and the properties of pristine graphene as well as the rising molecular graphenes.

Focus on synthesis, characterization and applications of low dimensional nanomaterials

Abstract This Editorial summarizes the content of a focus collection on the synthesis, characterization and applications of low dimensional materials. The collection groups original research and review articles providing recent results and prospects in the field, with particular attention on optoelectronic applications, dielectric and magnetic properties, and electrochemical and biological performances.

Green synthesis of fluorescent N-doped carbon quantum dots from castor seeds and their applications in cell imaging and pH sensing.

Water-soluble fluorescent N-doped carbon quantum dots (N-CQDs) were hydrothermally prepared through a green synthesis route using castor seeds as a single precursor and a hydrothermal method. Several experimental techniques have been used to characterize synthesized N-CQDs to confirm their structure and to verify their applicability in cell imaging and pH sensing. The synthesized N-CQDs were found to have are characterized by amorphous nature with a spherical shape with an average particle size of 6.57nm as revealed from XRD and TEM measurements. The FTIR results reveal the presence of carboxylic and hydroxyl functional groups on the surface of the CQDs, which was also confirmed by XPS analysis. The fluorescence characterization of the synthesized N-CQDs showed blue emission and excitation dependence with good photostability. It was found that the optimal excitation and emission wavelengths were (λEx = 360) and (λEm = 432) nm, respectively. The fluorescence quantum yield (QY) of about 9.6% at the optimum excitation wavelength 360nm. Moreover, the fluorescence intensity of N-CQDs showed good linear dependence with the pH values in ranges of 3.5 - 7.5 and 8 - 12 as well as high sensitivity for slight changes of pH values. According to these results, two fluorescent pH sensors were created based on acidic and basic media. The obtained N-CQDs have zeta potential of -21.86 mV and thus have excellent stability in water. Moreover, N-CQDs derived from the castor seeds have antimicrobial activity and exhibits low cytotoxicity to WI-13 cells with IC50 = 394.4 ± 13.8µg/mL. The results of this study demonstrated that the synthesized N-CQDs derived from castor seeds can be used as pH sensing and antimicrobial materials. On the other hand, they are also promising in applications in cell imaging, thermo-sensing and optoelectronics.

Intrinsic Rashba Effect in Stable Configurations of Two-Dimensional (PEA)2PbI4.

Halide perovskites (HPs) are crystalline solids that feature a unique softness, absent in conventional semiconducting materials. In recent years, this softness has been pivotal to many properties in these materials, in both static and dynamic regimes. Here, we focus on the two-dimensional (2D) (PEA)2PbI4 crystal. We employ extensive density functional theory calculations and structural analysis to uncover a rich mosaic of ground-state configurations, identifying several stable configurations with distinct electronic properties. Our study uncovers an intrinsic Rashba effect within a structure traditionally considered as globally centrosymmetric, presenting a challenge to conventional understanding in the field. The observed effect emerges from a local symmetry-breaking induced by specific spatial orientations of the organic PEA molecules. This intrinsic Rashba effect, observed in select configurations, underscores the nuanced symmetrical complexities of 2D HPs and highlights their potential for spin-related applications. Additionally, our investigation demonstrates the exceptional flexibility of 2D HPs, as evidenced by an observed significant tolerance toward single-molecule rotations. This flexibility suggests potential pathways for smoother transitions between different molecular domains within these materials. Overall, our findings emphasize the intricate interplay between the organic/inorganic counterparts and the electronic properties in 2D HPs, paving the way for further exploration and exploitation of their unique characteristics in various optoelectronic and spintronic applications.

Pressure-induced structural stability, metallization and optoelectronic properties of transition metal chalcogenide BaTiS3

The pressure effects on the structural stability, metallization and optoelectronic properties of transition metal chalcogenide BaTiS3 are investigated by performing ab-initio calculations. Our calculations show that BaTiS3 has a hexagonal structure at ambient pressure, which matches well with the available experimental values. As pressure increases, a transition from hexagonal to orthorhombic phase occurs at around 10.8 GPa. The band structure and density of states of hexagonal BaTiS3 have been calculated and analysed. Moreover, the effect of pressure on the optical properties has been studied in terms of dielectric function as well as absorption coefficient, reflectivity and extinction coefficient. The application of hydrostatic pressure has shifted the maximum absorption toward the visible range, revealing that hexagonal BaTiS3 can be used for high pressure optoelectronic applications.

Investigation of the Influence of Structure, Stoichiometry, and Synthesis Temperature on the Optical Properties of CdTe Nanoplatelets

Colloidal cadmium telluride (CdTe) nanoplatelets (NPLs) are promising materials for optoelectronic applications, such as photovoltaics and light-emitting diodes, due to their unique optical and electronic properties. However, controlling their growth, thickness, and stoichiometry remains challenging. This study explores the effect of synthesis temperature on the structural, optical, and stoichiometric properties of CdTe NPLs. CdTe NPLs were synthesized at temperatures of 170 °C, 180 °C, 190 °C, and 200 °C using colloidal methods. The resulting NPLs were characterized by UV–Vis absorption spectroscopy, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), and total reflection X-ray fluorescence (TXRF) to assess their morphology, structure, and elemental composition. The results showed that the synthesis temperature significantly affected the NPL’s morphology and stoichiometry. Optimal stoichiometry was achieved at 180 °C and 190 °C, with the crystal structure transitioning from zinc blende at lower temperatures to wurtzite at higher temperatures. Optical properties, including luminescence intensity and emission peaks, also varied with temperature. The synthesis temperature is an important parameter in controlling the structural and optical properties of CdTe NPLs. The optimal conditions for obtaining NPLs with the best characteristics were identified at 190 °C, presenting important findings for further optimization of CdTe NPL synthesis for optoelectronic applications.

Advancements in halide perovskite photonics

Halide perovskites have emerged as a new class of materials for photoelectric conversion, attracting an ever-increasing level of attention within the scientific community. These materials are characterized by expansive compositional choices, ease of synthesis, an impressively high light absorption coefficient, and extended carrier recombination lifetimes. These attributes make halide perovskites an ideal candidate for future optoelectronic and photonic applications, including solar energy conversion, photodetection, electroluminescence, coherent light generation, and nonlinear optical interactions. In this review, we first introduce fundamental concepts of perovskites and categorize perovskite photonic devices by the nature of their fundamental mechanisms, i.e., photon-to-electron conversion devices, electron-to-photon conversion devices, and photon-to-photon devices. We then review the significant progress in each type of perovskite device, focusing on working principles and device performances. Finally, future challenges and outlook in halide perovskite photonics will be provided.

Growth Phenomena and Bandgap Shift in Melt‐Grown β‐(InxGa1−x)2O3 Alloys

β‐Ga2O3 is an emerging ultra‐wide bandgap semiconductor with great promise for power electronics and optoelectronics. Alloys in the In2O3‐Ga2O3 system are interesting for optoelectronic applications, particularly where bandgap tuning is desirable. Herein, β‐(InxGa1–x)2O3 alloys with target compositions x = 0.025 or 0.10 are grown from the melt using the Czochralski and vertical gradient freeze techniques. Growth with 10 mol% In yields only small, needle‐like crystals, while 2.5 mol% In allows growth of centimeter‐sized single crystals. A substantial degree of indium segregation is unveiled by spatial measurements of lattice parameters and the bandgap. The bandgap decreases by a maximum of 0.28 eV in the case of the highest In content crystals. Z‐contrast transmission electron microscopy confirms a solely octahedral coordination of In in the β‐Ga2O3 lattice. With indium concentrations higher than 2.5 mol%, samples contain micron‐scale voids that impart a dark coloration. All measured crystals are electrically conductive, with carrier concentrations varying 1016–1017 cm−3 depending upon the location of the sample in the growth. Lastly, a unique luminescence with unknown origin centered around 2.0 eV is revealed by photoluminescence spectroscopy.

First-Principles Investigation of the OsI$$_{2}$$ Monolayer: A Novel Two-Dimensional Dihalide Material for Optoelectronic Applications

First-Principles Investigation of the OsI$$_{2}$$ Monolayer: A Novel Two-Dimensional Dihalide Material for Optoelectronic Applications

First principles investigations on structural, electronic, optical, and thermodynamical properties of bulk and surfaces of In2CO

This study reports first-principles investigations of the structural, electronic, thermal, and optical properties of a novel material In2CO in bulk phase and slab models in (001), (100), (101), and (011) orientations to develop a fundamental understanding of its characteristics. The material appeared structurally as well as dynamically stable in the orthorhombic phase. The thermal properties demonstrated that the material's heat capacity is more temperature-sensitive than entropy and enthalpy. The electronic band structure analysis revealed that the orthorhombic phase material is a semiconductor with a narrow indirect band gap. The electronic structures modeled using the spin-orbit coupling yielded the metallic phase of the slabs except for (001) orientation. The electromagnetic absorption characteristics of the compound are also investigated to explore the material's potential in optoelectronic applications. The direction-dependent study of optical characteristics revealed that the (001) slab of the material can be an efficient infrared detector. The survey findings provide instrumental outcomes in utilizing In2CO in electronic and optoelectronic applications.

Impact of metal deposition on the optical and interface properties of NiO: growth and characterization of NiO/metal thin bilayer films

Abstract Since transparent conductive oxides (TCOs) provide electrical conductivity together with optical transparency, they have found wide applications in optoelectronic devices and photovoltaics. Among the TCOs, nickel oxide (NiO) is challenging due to its inherent trade-off between transparency and electrical conductivity. To address this challenge, one effective approach is to deposit a metal layer onto NiO thin films. In this work, NiO, NiO/Au, NiO/Ag, and NiO/Cu thin films are prepared by sputtering and thermal evaporation techniques on glass substrates and fully characterized finding the proper film for optoelectronic applications. The electrical and optical properties of the fabricated films are examined by four-point probe measurements and optical spectrometry. According to the obtained results, the NiO/Au, NiO/Ag, and NiO/Cu bilayers show sheet resistance of 200, 338, and 925 Ω sq−1 respectively while their optical bandgaps vary from 3.2 to 3.76 eV. These findings provide valuable insights into the performance of these films, making them potentially viable choices for various optoelectronic applications.

Unraveling the Facet-Dependent Surface Chemistry at Molecular Scale: Photoassisted Oxidation of InP Nanocrystals.

The facet-dependent surface chemistry of nanocrystals (NCs) provides fundamental insights into chemical reactivities, which are critical for obtaining precise control over the NC surface. In this study, by obtaining InP NCs with well-defined {111} and {110}/{-1-1-1} facets (tetrahedrons and tetrapods, respectively) capped with chloride-oleylamine ligands, the previously underinvestigated facet-dependent surface chemistry of III-V materials is explored. Solid-state and solution NMR analyses show that InP tetrahedrons, with their smaller surface heterogeneity (single facet composition and lesser edge/vertex contribution) and stronger Lewis acidity, exhibit narrow 31P and 115In resonances as well as deshielded 13C signals of α-carbon adjacent to the NH2 group of oleylamine. As a result, InP tetrahedra exhibit strong ligand binding and a notable presence of less-mobile oleylamine ligands on the surface, leading to the blocking of access to external species. This is also consistent with the minimal blue shift of the first excitonic peak in absorption spectra and the strong resistance to photoassisted surface oxidation of InP tetrahedrons. Our findings, supported by solid-state/solution NMR, FT-IR, and XPS analyses, highlight the significance of facet-dependent reactivities to surface ligands and, thus, atmospheric moieties, enhancing the potential of III-V NCs in various optoelectronic applications.