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Transient absorption (TA) spectroscopy is one of the most popular experimental methods to measure the excited state lifetimes and charge carrier recombination mechanisms in two dimensional (2D) semiconductors. This fundamental information is essential for designing and optimizing the next generation of ultrathin and lightweight 2D semiconductor-based optoelectronic devices. However, the interpretation of TA spectroscopy data varies across the community. The community lacks a unifying physical explanation for how and why experimental variables such as incident light intensity, sample-substrate interactions, and/or applied bias affect TA spectral data. This Perspective (1) compares the physical chemistry TA literature to nanomaterial physics literature from a historical perspective, (2) reviews multiple physical explanations that the TA community developed to explain spectral features and experimental trends, (3) provides a unifying explanation for how and why trions—and, more generally, Fermi polarons—contribute to TA spectra, and (4) quantifies the extent to which various physical interpretations and data analysis procedures yield different timescales and mechanisms for the same set of experimental results. We highlight the importance of considering trions/Fermi polarons in TA measurements and their implications for advancing our understanding of 2D material properties. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite CsPbBr3 nanocrystals (NCs) display high photoluminescence quantum yield and narrow emission, which show great potential application in optoelectronic devices. However, the poor environment stability of NCs will hinder their practical application. Herein, a series of ionic liquids with different anions (BF4−, Br−, and NO3−) were used as a sole capping ligand to synthesize NCs. Among the three samples, 1-hexadecyl-3-methylimidazolium tetrafluoroborate ([C16MIM]BF4) capped NCs have the highest stability in light, thermal, and water, possibly attributing to the in situ passivation of bromine vacancy via pseudohalogen BF4− and tight binding of ionic liquid ligands and lead atoms. In addition, green-emission [C16MIM]BF4 NCs were used to assemble a white light-emitting diode device, and it possessed a wide National Television System Committee color gamut of 124.5% and a stable emission peak at high driving currents of 380 mA. This work paves the way for resurfacing perovskite NCs with ultrahigh stability, thereby driving the perovskite NC display industry closer to real-world application. [ABSTRACT FROM AUTHOR]

Nanotechnology's impact on semiconductor industry advancement, particularly through the engineering of nanostructures like nanowires, opens new possibilities for material functionality due to the tunable physical properties of nanostructures compared to bulk materials. This paper presents a comprehensive study on group IV semiconductors and their binaries across four polytypes: 2H, 3C, 4H, and 6H, focusing on their optoelectronic application potential. Deep understanding of these polytypes is particularly relevant for nanowire-based technologies. Through first principles modeling, we examine the structural and electronic properties of these materials, emphasizing their band structure, stability, and the feasibility for light-emitting applications. We use a generalized Ising model to discuss materials stability and tendency for polytypism. We also determine relative band edge positions and employ a six-band k⋅p model for a detailed understanding of the materials' electronic properties. Due to the comprehensive nature of this study, we provide insight on the chemical trends present in all of the studied properties. Our theoretical predictions align well with the existing experimental data, suggesting new avenues for nanostructure-based device development. The discussion extends to the implications of these findings for the fabrication of optoelectronic devices with the studied IV–IV materials, highlighting the challenges and opportunities for future research in nanowire synthesis and their applications. [ABSTRACT FROM AUTHOR]

The monolayer metamaterial that consists of graphene arrangement squares and four L-shaped graphene blocks is designed to achieve quintuple plasmon-induced transparency (quintuple-PIT). First, the accuracy of the results has been validated through finite difference time domain simulations and coupled mode theory, which show good agreement. Second, a quadruple-frequency asynchronous switch with amplitude modulation degree (AMD) values of 94.7%, 91.1%, 96.6%, and 77.4% and a sextuple-frequency synchronous switch with AMD values of 95.0%, 96.8%, 88.0%, 93.3%, 58.6%, and 71.5% have been proposed by dynamic control, respectively. It is worth noting that the number of PIT windows in the transmission curve can be freely adjusted from a quintuple-PIT to single-PIT mode by manipulating the Fermi level states of different parts of the structure. Finally, further investigations have demonstrated that the proposed structure exhibits excellent slow-light properties and is insensitive to polarized light, which indicates that the metamaterial structure possesses good stability and anti-interference capabilities under various polarization conditions. The metamaterial and results provide valuable insights and ideas for the design of optoelectronic devices. [ABSTRACT FROM AUTHOR]

Exploring potential two-dimensional monolayers with large photogalvanic effect (PGE) has been of great importance for developing self-powered optoelectronic devices. In this paper, we systematically investigate the generation of PGE photocurrent in chalcogen-based Janus XYZ monolayers (X/Y/Z = S, Se, Te; X ≠ Y ≠ Z) based on non-equilibrium Green's function formalism with density functional theory. The optimized Janus SSeTe, SeSTe, and TeSeS monolayers in the rectangular phase are shown stable and, respectively, possess 1.54, 1.49, and 1.74 eV indirect bandgaps. Illuminated by linearly polarized light, the PGE photocurrent without bias voltage can be collected in both armchair and zigzag directions. Unlike common Janus 2D materials with C3v symmetry, the photocurrent peak values of Janus XYZ monolayers do not come up with certain polarization angles, while the relations can be fitted by Iph = α sin(2θ) + β cos(2θ) + γ at each photon energy. Meanwhile, the maximum photoresponses of Janus SSeTe, SeSTe, and TeSeS monolayers are 2.02, 3.33, and 4.42 a20/photon, respectively. The relatively large PGE photocurrents and complicated polarization relations result from the lower symmetry of Janus XYZ monolayers. Moreover, the specific polarization angles for maximum photoresponses at each photon energy and the ratio between two transport directions are demonstrated, reflecting the anisotropy. Our results theoretically predict a potential Janus monolayer family for self-powered optoelectronic applications. [ABSTRACT FROM AUTHOR]

The non-radiative energy transfer process governs the transport of excitons in organic semiconductors, directly affecting the performance of organic optoelectronic devices. Successful models describe this transfer in terms of energy donor–acceptor pair sites, in contrast to experimental photophysical properties, which reflect the average behavior of the molecular ensemble. In this study, an energetic and spatial probability density function is proposed to determine the average non-radiative energy rate for homotransfer processes. This approach considers the energetic-spatial distribution typical of disordered semiconducting polymers. The average homotransfer rate is significantly dependent on the energy of the donor site, allowing the identification of the photophysical process most likely to occur. Values of the order of 1011 s−1 were predicted and are consistent with experimental results. This approach was used to evaluate how the energy transfer efficiency in heterostructures is affected by the energy and position of the energy donor site. The model presented in this study can be explored in other organic systems to investigate exciton transport mechanisms in new organic optoelectronic device architectures. [ABSTRACT FROM AUTHOR]

Photoexcitation is a powerful way to induce phase transition of strongly correlated materials and dynamically control terahertz (THz) devices integrated with photoinduced phase transition (PIPT) materials. To clarify controversies over the physical mechanism between electronic insulator-metal transition (IMT) and structural phase transition (SPT) of photoexcited vanadium dioxide (VO 2), the underlying atomic and electronic state changes during photoinduced monoclinic-to-rutile phase transition are illustrated, and the separation with different thresholds between the quasi-instantaneous IMT and the ultrafast SPT is discovered. Below the SPT threshold, there exist metastable states exhibiting the metal-like monoclinic phases, i.e., the strongest metallicity and weak monoclinic phases, when the bond lengths of the V–V pairs are closest. By analyzing the electronic transport properties of these metal-like monoclinic phases, the THz response of the whole phase transition process can be characterized for first time through the quantum-electromagnetic dispersion modeling method. The THz properties of the practical VO 2 film are simulated and the great alignments between the measurements and the simulations verify the proposed analysis method, which provides a powerful exploration path and insights for the theoretical analysis and design verification of PIPT materials and their optoelectronic THz devices. [ABSTRACT FROM AUTHOR]

α-Al2O3 is renowned for its extensive bandgap and diverse applications in electronic and optoelectronic devices. Employing density-functional theory-based methods, this study investigates the feasibility of chalcogen doping (S, Se, Te) in α-Al2O3. Standard modeling tools are utilized to construct α-Al2O3 supercells, focusing on the calculations of individual chalcogen-related and native point defects resulting from single-atom doping. Our analysis systematically explores the formation energies and transition levels associated with chalcogen (S, Se, Te) doping in oxygen (or aluminum) sites in Al-rich (or O-rich) limits. We observe a trend where increasing atomic number (from S to Te) correlates with a higher difficulty in forming anion-doped α-Al2O3, but a lower barrier to cationic doping. The results indicate a preferential substitution of chalcogen atoms for aluminum in O-rich environments. Specifically, in varying oxygen conditions, the dominant defect types, their prevalence, and defect formation energies in α-Al2O3 are significantly altered following chalcogen doping, offering new insights into defect processes in α-Al2O3. [ABSTRACT FROM AUTHOR]

α-Al2O3 is renowned for its extensive bandgap and diverse applications in electronic and optoelectronic devices. Employing density-functional theory-based methods, this study investigates the feasibility of chalcogen doping (S, Se, Te) in α-Al2O3. Standard modeling tools are utilized to construct α-Al2O3 supercells, focusing on the calculations of individual chalcogen-related and native point defects resulting from single-atom doping. Our analysis systematically explores the formation energies and transition levels associated with chalcogen (S, Se, Te) doping in oxygen (or aluminum) sites in Al-rich (or O-rich) limits. We observe a trend where increasing atomic number (from S to Te) correlates with a higher difficulty in forming anion-doped α-Al2O3, but a lower barrier to cationic doping. The results indicate a preferential substitution of chalcogen atoms for aluminum in O-rich environments. Specifically, in varying oxygen conditions, the dominant defect types, their prevalence, and defect formation energies in α-Al2O3 are significantly altered following chalcogen doping, offering new insights into defect processes in α-Al2O3. [ABSTRACT FROM AUTHOR]

Photoexcitation is a powerful way to induce phase transition of strongly correlated materials and dynamically control terahertz (THz) devices integrated with photoinduced phase transition (PIPT) materials. To clarify controversies over the physical mechanism between electronic insulator-metal transition (IMT) and structural phase transition (SPT) of photoexcited vanadium dioxide (VO 2), the underlying atomic and electronic state changes during photoinduced monoclinic-to-rutile phase transition are illustrated, and the separation with different thresholds between the quasi-instantaneous IMT and the ultrafast SPT is discovered. Below the SPT threshold, there exist metastable states exhibiting the metal-like monoclinic phases, i.e., the strongest metallicity and weak monoclinic phases, when the bond lengths of the V–V pairs are closest. By analyzing the electronic transport properties of these metal-like monoclinic phases, the THz response of the whole phase transition process can be characterized for first time through the quantum-electromagnetic dispersion modeling method. The THz properties of the practical VO 2 film are simulated and the great alignments between the measurements and the simulations verify the proposed analysis method, which provides a powerful exploration path and insights for the theoretical analysis and design verification of PIPT materials and their optoelectronic THz devices. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) Ruddlesden−Popper phase all-inorganic halide perovskite Cs2PbI2Cl2 has attracted tremendous attention because of its high carrier mobility, strong light-absorbing ability, and excellent environmental stability, possessing enormous potential for use as a high-performance optoelectronic device. Here, we present two transistor devices based on monolayer (ML) Cs2PbI2Cl2 and reveal their performance and current transport mechanisms through ab initio quantum transport calculations. The n-type 10 nm metal-oxide-semiconductor field-effect transistor shows a high on-state current Ion of 3160 μA/μm, and excellent performance regarding subthreshold swing, intrinsic delay time (τ), and power consumption, which completely match the International Roadmap for Device and Systems (2021 version) targets for high-performance devices and low-power devices in 2028. Moreover, phototransistors based on monolayer Cs2PbI2Cl2 also display a strong response to UV light, with a light-to-dark current ratio reaching a maximum of 104. Meanwhile, a high specific detectivity of 2.45 × 1011 Jones is obtained. The results of our study suggest that ML Cs2PbI2Cl2 is a promising candidate for high-performance transistors. [ABSTRACT FROM AUTHOR]

We demonstrate the change of the sign from negative to positive of the self-powered photovoltaic photocurrent in core–shell n-InGaN/p-GaN nanowire heterojunctions within the visible to UV wavelength range. Such dual-polarity photodetectors are of broad interest to provide extended functionalities for optoelectronic devices, starting with dual-wavelength photodetectors. The physics of the photocurrent sign reversal is understood by a well-balanced selective absorption and photocarrier generation, photocarrier transfer, and thermal excitation paths in the core–shell n-InGaN/p-GaN nanowire functional absorber with different bandgap energies and opposite inner- and surface energy band bendings. The basic dual-wavelength photodetector operation parameters are given. [ABSTRACT FROM AUTHOR]

A comprehensive study on the photo-excited relaxation dynamics in semiconducting perovskite quantum dots (PQDs) is pivotal in realizing their extensive potential for optoelectronics applications. Among different competing photoinduced relaxation kinetics, energy transfer and charge transfer (CT) in PQDs need special attention, as they often influence the device efficacy, particularly with the donor–acceptor hybrid architecture. In this work, we explore a detailed investigation into photoinduced CT dynamics in mixed halide undoped CsPb(Br/Cl)3 and Mn2+ doped CsPb(Br/Cl)3 PQDs with a quinone molecule, p-benzoquinone (BQ). The energy level alignment of undoped PQDs with BQ allows an efficient CT, whereas Mn2+ doping reduces the CT efficiency, experiencing a competition between energy transfer from host to dopant and CT to BQ. The conductive atomic force microscopy measurements unveil a direct correlation with the spectroscopic studies by showing a significant improvement in the conductance of undoped PQDs in the presence of BQ, while an inappreciable change is observed for doped PQDs. A much-reduced transition voltage and barrier height in the presence of BQ further validate faster CT for undoped PQD than the doped one. Furthermore, Mn2+ doping in PQDs is observed to enhance their stability, showing better air and thermal stability compared to their undoped counterparts. These results reveal that doping strategy can regulate the CT dynamics in these PQDs and increase their stability, which will be beneficial for the development of desired optoelectronic devices with long-term stability. [ABSTRACT FROM AUTHOR]

Two-dimensional or other thin materials have high potential for use in next-generation electronic and optoelectronic devices. Recently, tellurium has gained much interest due to its broad applicability prospects. In this work, the physical properties of thin tellurium layers fabricated using two relatively simple and inexpensive technologies based on the deposition from a chemical solution and by thermal evaporation were compared. The morphology of the grown surfaces was analyzed using atomic force microscopy. The chemically deposited tellurium surface consists of nanometer-sized flakes, while polycrystalline layers are formed in the case of deposition by thermal evaporation. Additionally, the characteristics of the fabricated samples varied depending on their thickness, as observed in both Raman spectroscopy and THz spectroscopy measurements. Furthermore, the non-contact optical pump THz probe technique revealed that the layers had different carrier lifetimes and mobilities. The carrier lifetime of samples deposited by thermal evaporation is short, less than 40 ps, with mobility up to a few hundred cm2/V s. In contrast, chemically deposited samples have a longer carrier lifetime, ranging more than 500 ps, and superior mobility up to 1000 cm2/V s. [ABSTRACT FROM AUTHOR]

Photocurrent measurements are widely used to study the intrinsic optoelectronic properties of semiconductors, such as photocarrier generation efficiency and carrier mobility, as well as evaluate the performance of optoelectronic devices, such as solar cells and photodetectors. Interferometric spectroscopy precisely measures optical properties and gathers optical spectra information on semiconductors. Consequently, photocurrent-based interferometric measurements, with high signal-to-noise ratios, high resolution, and broad frequency bandwidths, can probe the energy distributions of low-density defects and impurities and investigate charge transport in materials and devices. Here, we demonstrate that photocurrent interference spectroscopy reveals the intrinsic properties of solar-cell materials: bulk crystals of GaAs and halide perovskite, and thin films of halide perovskite and quantum dot. We show that homodyne interference spectroscopy of photocurrent can monitor low-density localized states in semiconductors and that it can be used in combination with other spectroscopy techniques, such as photoluminescence measurements, to provide a deep understanding of photocurrent generation processes. Furthermore, we show that heterodyne interference spectroscopy of photocurrent can be used to investigate the frequency dependence of material parameters, such as the dielectric constant, absorption coefficient, and reflectance. As an application, we used interference spectroscopy of photocurrent to show the impact of multiexcitons on the photoabsorption and photocarrier generation processes in quantum dot solar cells. Finally, we used it to reveal the distinctive spectral characteristics at the band edge of a halide perovskite, which is considered to be an exceptional solar-cell material with high energy conversion efficiency. [ABSTRACT FROM AUTHOR]

Here, a photodetector based on Au decorated MoS2/poly(3,4-ethylenedioxythiophene) poly(4-styrenesulfonate) PEDOT:PSS nanocomposite films (NCFs) were prepared and their ambipolar (negative and positive) photoresponse under UVC (220–300 nm) and UVA (320–400 nm) UV illumination by increasing the Au decoration on MoS2 in NCFs was reported. This unusual phenomenon relates to the confinement and trapping of charges induced by radiation and plasmons. The hydrothermal technique is employed for generating MoS2 nanosheets. Optical studies reveal the observable bandgap difference resulting from the addition of increasing Au decoration on MoS2 in NCFs. Fourier transform infrared spectroscopy investigations are conducted to comprehend the vibrational characteristics of the produced samples. Carrier localization and trapping generated by photoexcitation and plasmon-induced ambipolar photoresponses provide a versatile control parameter. These results provide opportunities for the application of NCF material in electrical, optical, and optoelectronic devices. The results of this work broaden the pool of potential materials for UVC and UVA photodetectors, perhaps providing new perspectives on the photoresponse of the NCF. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a class of intriguing materials with tunable electronic and optical properties. In this work, we investigate the electronic and optical properties of COFs embedded with hBN and graphene. Our results demonstrate that graphene integration enhances the ultraviolet and visible light absorption of C 6 N 6 and B 6 O 6 monolayers, while charge transfer in all COF/graphene heterostructures leads to the formation of a built-in electric field. Furthermore, we show that incorporating hBN into B 6 O 6 and C 6 N 6 heterostructures enables control of their bandgap through an applied electric field, resulting in a semiconductor-to-metal transition under moderate electric field strengths. Additionally, B 6 O 6 /hBN exhibits suitable band edge alignment for photocatalytic water splitting. These findings provide valuable insights into the electronic and optical properties of COF heterostructures and their potential applications in electronic and optoelectronic devices. Our study contributes to ongoing efforts in the design and development of novel COF and 2D material heterostructures for future electronic and photonic applications. [ABSTRACT FROM AUTHOR]

For rooting the development of GaN-based optoelectronic devices, understanding the roles of midgap recombination centers (MGRCs), namely, nonradiative recombination centers and deep-state radiative recombination centers, on the carrier recombination dynamics is an essential task. By using the combination of time-resolved photoluminescence and positron annihilation spectroscopy (PAS) measurements, the origins of major MGRCs in the state-of-the-art GaN epilayers, bulk crystals, and Mg-implanted layers were identified, and their concentrations were quantified for deriving the capture coefficients of minority carriers. In this article, potential standardization of the room-temperature photoluminescence lifetime for the near-band-edge emission (τ PL RT ) as the concentration of major MGRCs well below the detection limit of PAS is proposed. For n-GaN substrates and epilayers grown from the vapor phase, τ PL RT was limited by the concentration of carbon on N sites or divacancies comprising a Ga vacancy (VGa) and a N vacancy (VN), [VGaVN], when carbon concentration was higher or lower, respectively, than approximately 1016 cm−3. Here, carbon and VGaVN act as major deep-state radiative and nonradiative recombination centers, respectively, while major MGRCs in bulk GaN crystals were identified as VGa(VN)3 vacancy clusters in Na-flux GaN and VGa or VGaVN buried by a hydrogen and/or VGa decorated with oxygen on N sites, VGa(ON)3–4, in ammonothermal GaN. The values of τ PL RT in n-GaN samples are compared with those of p-GaN, in which τ PL RT was limited by the concentration of VGa(VN)2 in Mg-doped epilayers and by the concentrations of VGaVN and (VGaVN)3 in Mg-implanted GaN right after the implantation and after appropriate activation annealing, respectively. [ABSTRACT FROM AUTHOR]

Understanding excited-state intramolecular proton transfer (ESIPT) is essential for designing organic molecules to enhance photophysical and luminophore properties in the development of optoelectronic devices. In this context, an attempt has been made to understand the impact of substituents on the ESIPT process of 2-(oxazolinyl)-phenol. Electron donating (EDG: –NH2, –OCH3, and –CH3) and electron withdrawing (EWG: –Cl, –Br, –COOH, –CF3, –CN, and –NO2) substitutions have been computationally designed and screened through density functional theory (DFT) and time-dependent density-functional theory (TDDFT) calculations. Furthermore, the ground state intramolecular proton transfer and ESIPT mechanisms of these designed luminophores are explored using the transition state theory. The results reveal that molecules with EDG show higher absorption and emission peaks than molecules with EWG and also indicate that the mobility of charge carriers in 2-(oxazolinyl)-phenol derivatives is significantly influenced by substituents. We found that the EWGs decrease the reorganization energy and increase the vertical ionization potential and electron affinity values, as well as the highest occupied molecular orbital-lowest unoccupied molecular orbital gap, compared to the EDG substituted molecules. Significantly, the excited state (S1) of the keto emission (K) form shows notably larger values for the EDG substitutions. The intersystem crossing pathway efficiency weakens with reduced spin–orbit coupling matrix element in the enol form with electron-donating substituents and vice versa in the keto form during S1–T3 transitions. Our research links intramolecular proton transfers and triplet generation, making these substituted molecules appealing for optoelectronic devices. Introducing EDGs, such as –NH2, boosts the ESIPT reaction in 2-(oxazolinyl)-phenol. This study guides designing ESIPT emitters with unique photophysical properties. [ABSTRACT FROM AUTHOR]

In recent years, inorganic lead-free perovskite materials have garnered attention for their non-toxicity, high carrier mobility, and strong light absorption capabilities, showing promising application prospects in photoelectric sensing. CsCu2I3 perovskite has been mentioned as one of the representatives and as a potential material for short-wavelength optoelectronic devices. This study employs a one-step chemical vapor deposition (CVD) process to fabricate CsCu2I3 thin films, which exhibit a vibrant yellow emission at 560 nm. Ultraviolet photodetectors utilizing CsCu2I3 films demonstrate an exceptional responsivity and a detectivity of 1.43 A/W and 1.15 × 1012 Jones (254 nm, 5 V bias), along with rapid response times (trise ≈ 50 ms, tdecay ≈ 70 ms). Moreover, this work examines the factors affecting device performance, including wavelength, operating voltage, and film thickness. It presents a straightforward, ecofriendly CVD method for producing lead-free perovskite films and optoelectronic devices, which has significant implications for the development of lead-free perovskite-based photoelectric technologies. [ABSTRACT FROM AUTHOR]

First-principles calculations of defects and electron–phonon interactions play a critical role in the design and optimization of materials for electronic and optoelectronic devices. The late Audrius Alkauskas made seminal contributions to developing rigorous first-principles methodologies for the computation of defects and electron–phonon interactions, especially in the context of understanding the fundamental mechanisms of carrier recombination in semiconductors. Alkauskas was also a pioneer in the field of quantum defects, helping to build a first-principles understanding of the prototype nitrogen-vacancy center in diamond, as well as identifying novel defects. Here, we describe the important contributions made by Alkauskas and his collaborators and outline fruitful research directions that Alkauskas would have been keen to pursue. Audrius Alkauskas' scientific achievements and insights highlighted in this article will inspire and guide future developments and advances in the field. [ABSTRACT FROM AUTHOR]

The trap centers have a significant impact on the electronic properties of lead tungstate (PbWO4), suggesting their crucial role in optoelectronic applications. In the present study, we investigated and revealed the presence of shallow trap centers in PbWO4 crystals through the utilization of the thermally stimulated current (TSC) method. TSC experiments were performed in the 10–280 K range by applying a constant heating rate. The TSC spectrum showed the presence of a total of four peaks, two of which were overlapped. As a result of analyzing the TSC spectrum using the curve fit method, the activation energies of revealed centers were found as 0.03, 0.11, 0.16, and 0.35 eV. The trapping centers were associated with hole centers according to the comparison of TSC peak intensities recorded by illuminating the opposite polarity contacts. Our findings not only contribute to the fundamental understanding of the charge transport mechanisms in PbWO4 crystals but also hold great promise for enhancing their optoelectronic device performance. The identification and characterization of these shallow trap centers provide valuable insights for optimizing the design and fabrication of future optoelectronic devices based on PbWO4. [ABSTRACT FROM AUTHOR]

III–V colloidal quantum dots (QDs) promise Pb and Hg-free QD compositions with which to build short-wavelength infrared (SWIR) optoelectronic devices. However, their synthesis is limited by the availability of group-V precursors with controllable reactivities to prepare monodisperse, SWIR-absorbing III–V QDs. Here, we report a one-pot heat-up method to synthesize ∼8 nm edge length (∼6.5 nm in height) tetrahedral, SWIR-absorbing InAs QDs by increasing the [In3+]:[As3+] ratio introduced using commercially available InCl3 and AsCl3 precursors and by decreasing the concentration and optimizing the volume of the reducing reagent superhydride to control the concentration of In(0) and As(0) intermediates through QD nucleation and growth. InAs QDs are treated with NOBF4, and their deposited films are exchanged with Na2S to yield n-type InAs QD films. We realize the only colloidal InAs QD photoconductors with responsivity at the technologically important wavelength of 1.55 μm. [ABSTRACT FROM AUTHOR]

The spin control possibility and its application in optoelectronic devices began an intensive research into its utilization, in particular, in the wide-gap semiconductors such as GaN doped with transition metal ions. Due to a strong p–d hybridization in Ga1−xMnxN, the Curie temperature above 300 K was already expected for x = 5%, providing that the free hole concentration necessary for the hole-mediated ferromagnetism exceeds 1020 cm−3. In this context, the development of non-equilibrium techniques enabled the engineering high-quality epitaxial layers of (Ga,Mn)N exhibiting uniform ferromagnetism at low-end cryogenic temperatures. The Tutorial is focused on the molecular beam epitaxy growth method of the Mn-enriched GaN magnetic semiconductors, summarizes the (Ga,Mn)N structural and electronic studies, and explains fundamental ferromagnetic properties, including the determination of the Mn concentration and the Curie temperature based on magnetic measurements. Most studies reveal the homogenous substitution of Mn3+ ions in the GaN matrix. Nevertheless, achieving room-temperature ferromagnetism still remains a challenge. Therefore, in the Tutorial, future research is suggested that can help obtain the homogenous ferromagnetism in (Ga,Mn)N at much elevated temperatures. [ABSTRACT FROM AUTHOR]

The acidic (pKa ≈ 1.5 – 2.5) and hygroscopic nature of poly(3,4-ethylene dioxythiophene) polystyrene sulfonate, used as a common hole-injection layer in optoelectronic devices, has a detrimental effect on device stability and is associated with well established device failure mechanisms. In this work, a process with a high green index hole-injection layer material (V 2 O 5) and low surface roughness (RMS roughness ≈ 1.3 nm) was developed for demonstrating a hybrid polymer–inorganic perovskite light-emitting diode. Test devices with the new hole-injection layer demonstrate nearly identical maximum current efficiencies (4.23 vs 4.19 cd/A), and luminous efficacies (2.99 vs 2.32 lm/W) when compared to a control device fabricated with the conventional hole-injection layer. Furthermore, the peak brightness was achieved at a current density one-third of the value for the control device. To examine the transport of holes in the above hole-injection layer, we carried out device simulations based on a physical charge control model, including defect-assisted tunneling for hole injection. Close agreement for current–voltage characteristics is observed. Experimentally measured mobility in the device and measured radiative lifetimes were found to be sufficient to achieve this agreement without resorting to the introduction of a sheet charge at the injection interface. Despite the use of a bulk-heterojunction device architecture, the model predicts high radiative recombination rates [ ≈ 5.6 × 10 22 /(cm 3 s)] in the emissive layer, consistent with the measured photophysical properties for the active film, suggesting effective passivation of non-radiative surface states. [ABSTRACT FROM AUTHOR]

Highly degenerate n-type CdO with high electron mobility is a promising transparent conducting oxide (TCO) for optoelectronic devices utilizing a spectrum in the Vis-NIR range. In particular, it has been shown that doped CdO thin films can show much superior transparency of >80% in the NIR region compared to conventional transparent conducting oxide (e.g., Sn-doped In2O3) thin films with a similar sheet resistance. However, CdO thin films typically experience rapid degradation in their electron mobilities when exposed to environmental conditions with H2O moisture. Here, we studied the effects of thermal annealing on the environmental stability of In-doped CdO (CdO:In) using a combination of different analytical techniques. CdO:In thin films with different In concentration (0%–8.3%) synthesized by magnetron sputtering were subjected to different post-thermal annealing (PTA) and then aged in different environmental conditions with varying relative humidity (RH) in the range of 0%–85%. Our results reveal that the degradation of CdO:In thin films can be primarily attributed to the oxygen vacancy-related defects at the grain boundaries, which can readily react with the OH− in the moisture. The moisture induced degradation can be mitigated by appropriate PTA at high temperatures (>400 °C) where grain boundary defects, primarily associated with Cd vacancies, can be passivated through hydrogen (H), thus enhancing their environmental stability. The present study provides a comprehensive understanding of the instability mechanisms and defect passivation in transparent conducting CdO:In thin films, which can also be relevant for other wide gap oxides. [ABSTRACT FROM AUTHOR]

The discovery of strontium niobate (SNO) as a potentially new transparent electrode has generated much interest due to its implications in various optoelectronic devices. Pristine SNO exhibits exceptionally low resistivity (∼10−4 Ω cm) at room temperature. However, this low resistivity occurs due to large number of carrier concentration in the system, which significantly affects its optical transparency (∼40%) in the visible range and hinders its practical applications as a transparent electrode. Here, we show that modulating the growth kinetics via oxygen manipulation is a feasible approach to achieve the desired optoelectronic properties. In particular, epitaxial (001) SNO thin films are grown on (001) lanthanum aluminate by pulsed laser deposition at different oxygen partial pressures and are shown to improve the optical transparency from 40% to 72% (λ = 550 nm) at a marginal cost of electrical resistivity from 2.8 to 8.1 × 10−4 Ω cm. These changes are directly linked with the multi-valence Nb-states, as evidenced by x-ray photoelectron spectroscopy. Furthermore, the defect-engineered SNO films exhibit multiple electronic phases that include pure metallic, coexisting metal-semiconducting-like, and pure semiconducting-like phases as evidenced by low-temperature electrical transport measurements. The intriguing metal-semiconducting coexisting phase is thoroughly analyzed using both perpendicular and angle-dependent magnetoresistance measurements, further supported by a density functional theory-based first-principles study and the observed feature is explained by the quantum correction to the conductivity. Overall, this study shows an exciting avenue for altering the optical and transport properties of SNO epitaxial thin films for their practical use as a next-generation transparent electrode. [ABSTRACT FROM AUTHOR]

Graphene has been a subject of great interest not only due to its fascinating properties but also for being the pioneer among 2D van der Waals (vdW) materials. Hexagonal boron nitride, an isomorph of graphene and a wide gap insulator, is commonly referred to as white graphene. The combination of the insulating hexagonal boron nitride (h-BN) with other crystals to form heterostructures provide a path for engineering and manipulating new physics and device properties. In this work, we investigate the vdW heterostructures formed by assembling h-BN and lizardite, a clay-mineral that is abundant in nature and represents the most stable polymorph of the serpentine family. The optoelectronic properties of three distinct heterostructures are presented to discern the characteristics of the systems. We observe that unlike lizardite and h-BN which are insulators, all the three heterostructures exhibit a semiconducting nature. The direct gap of the heterostructure in which two h-BN sheets are simultaneously placed above and below the octahedral and tetrahedral layers also makes it relevant for optoelectronic devices. Additionally, unlike lizardite, the heterostructures demonstrate a polarization-dependent optical properties. The study of the assembled structures combining the clay-mineral with h-BN not only widens the spectrum of vdW heterostructures but also explores their potential within the context of the serpentine family. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals have been under intense investigation for their promise in optoelectronic devices due to their remarkable physics, such as liquid/solid duality. This liquid/solid duality may give rise to their defect tolerance and other such useful properties. This duality means that the electronic states are fluctuating in time, on a distribution of timescales from femtoseconds to picoseconds. Hence, these lattice induced energy fluctuations that are connected to polaron formation are also connected to exciton formation and dynamics. We observe these correlations and dynamics in metal halide perovskite nanocrystals of CsPbI3 and CsPbBr3 using two-dimensional electronic (2DE) spectroscopy, with its unique ability to resolve dynamics in heterogeneously broadened systems. The 2DE spectra immediately reveal a previously unobserved excitonic splitting in these 15 nm NCs that may have a coarse excitonic structure. 2D lineshape dynamics reveal a glassy response on the 300 fs timescale due to polaron formation. The lighter Br system shows larger amplitude and faster timescale fluctuations that give rise to dynamic line broadening. The 2DE signals enable 1D transient absorption analysis of exciton cooling dynamics. Exciton cooling within this doublet is shown to take place on a slower timescale than within the excitonic continuum. The energy dissipation rates are the same for the I and Br systems for incoherent exciton cooling but are very different for the coherent dynamics that give rise to line broadening. Exciton cooling is shown to take place on the same timescale as polaron formation, revealing both as coupled many-body excitation. [ABSTRACT FROM AUTHOR]

We investigated the chemical beam epitaxy of GaP 1 − x N x grown on nominally (001) -oriented Si substrates, as desired for the lattice-matched integration of optoelectronic devices with the standard Si technology. The growth mode and the chemical, morphological, and structural properties of samples prepared using different growth temperatures and N precursor fluxes were analyzed by several techniques. Our results show that, up to x ≈ 0.04 , it is possible to synthesize smooth and chemically homogeneous GaP 1 − x N x layers with a high structural quality. As the flux of the N precursor is increased at a given temperature to enhance N incorporation, the quality of the layers degrades upon exceeding a temperature-dependent threshold; above this threshold, the growing layer experiences a growth mode transition from 2D to 3D after reaching a critical thickness of a few nm. Following that transition, the morphology and the chemical composition become modulated along the [ 110 ] direction with a period of several tens of nm. The surface morphology is then characterized by the formation of { 113 } -faceted wires, while the N concentration is enhanced at the troughs formed in between adjacent (113) and (1 ¯ 1 ¯ 3). On the basis of this study, we conclude on the feasibility of fabricating homogeneous thick GaP 1 − x N x layers lattice matched to Si (x = 0.021) or even with N content up to x = 0.04. The possibility of exceeding a N mole fraction of 0.04 without inducing coupled morphological–compositional modulations has also been demonstrated when the layer thickness is kept below the critical value for the 2D–3D growth mode transition. [ABSTRACT FROM AUTHOR]

The transition of energy from the 4f to the 5d state is a fundamental element driving various applications, such as phosphors and optoelectronic devices. The positioning of the 4f ground states and the 5d excited states significantly influences this energy shift. In our research, we delve into the placement of these states utilizing a hybrid density functional theory (DFT) combined with spin–orbit coupling (SOC) via the supercell method. Additionally, we scrutinize the transition energy, applying the constrained density functional theory (cDFT) approach in conjunction with the ΔSCF method. Our study illustrates that the synergy of cDFT and SOC generates a discrepancy of about 2% for Ce1 and 4% for Ce2 when comparing the calculated results to experimental data. Moreover, We have determined the positions of the 4f ground states to be 2.73 eV above the Valence Band Maximum (VBM) for Ce1 and 2.70 eV for Ce2. We also note a tight correlation between the 5d levels identified in the experimental data and the theoretical outcomes derived from wave function calculations at the CASPT2 accuracy level. [ABSTRACT FROM AUTHOR]

The transition of energy from the 4f to the 5d state is a fundamental element driving various applications, such as phosphors and optoelectronic devices. The positioning of the 4f ground states and the 5d excited states significantly influences this energy shift. In our research, we delve into the placement of these states utilizing a hybrid density functional theory (DFT) combined with spin–orbit coupling (SOC) via the supercell method. Additionally, we scrutinize the transition energy, applying the constrained density functional theory (cDFT) approach in conjunction with the ΔSCF method. Our study illustrates that the synergy of cDFT and SOC generates a discrepancy of about 2% for Ce1 and 4% for Ce2 when comparing the calculated results to experimental data. Moreover, We have determined the positions of the 4f ground states to be 2.73 eV above the Valence Band Maximum (VBM) for Ce1 and 2.70 eV for Ce2. We also note a tight correlation between the 5d levels identified in the experimental data and the theoretical outcomes derived from wave function calculations at the CASPT2 accuracy level. [ABSTRACT FROM AUTHOR]

The lattice mismatch, defect, and weak interlayer coupling severely constrain the practical application of van der Waals heterojunctions (vdWHs) in the field of optoelectronic devices. Here, we introduced the 2D ferroelectric (FE) material AgBiP2Se6 to construct defect-free, low lattice-mismatched AgBiP2Se6/MoSe2 heterojunctions with different polariton directions (I, II, III). The AgBiP2Se6 layer can provide an excellent FE electric field to enhance the interlayer coupling and stiffness. The larger interlay stiffness reduces the probability of electron–phonon scattering and then results in significant carrier mobility (∼0.5 × 104 cm2 V−1 s−1) for configurations I and II. Phase transition of FE to paraelectric AgBiP2Se6 in the AgBiP2Se6/MoSe2 heterojunctions can be achieved under specific biaxial strain, which can effectively regulate the electronic structure. Applying the strain and electric field can regulate the bandgap and band alignment of configurations I and II. The photoelectric conversion efficiency of configuration I can reach as high as 20.54% under 2% biaxial strain. Furthermore, configuration II holds a nearly free electron state near the Fermi level under an electric field, which can act as a favorable electron transport channel. A design to strengthen interlayer coupling in the FE-based AgBiP2Se6/MoSe2 heterojunction has been proposed, and it can provide a new way to break through the traditional bottleneck in the development of optoelectronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] Photoelectric artificial synapses based on memristors is an effective method to realize neuromorphic computation. This study presents an optoelectronic responsive artificial synapse made of a composite material consisting of gelatin and carbon nanotubes. The memristor demonstrates characteristics of analog resistive switching, the ability to store multiple memory states, and impressive retention properties. It has the capability to induce an excitatory post-synaptic current by means of electrical pulses or pulsed light exposure. The excitatory post-synaptic current can be modulated by the number, amplitude and interval of electrical pulses, as well as the action time, interval and light intensity of optical pulses. The artificial synapse showcases the emulation of fundamental Hebbian learning protocols, including spike timing dependent plasticity and spike amplitude dependent plasticity. In addition, the charge transfer in the carbon nanotube gelatin composite optoelectronic memristor is investigated through first-principles calculations, shedding light on its operational mechanism. Experimental results show that these devices have the potential to be utilized for processing image information, resulting in a significant reduction of input data and training expenses when recognizing handwritten numbers. Overall, the optoelectronic synapse exhibits promising image processing prospects in the field of neuromorphic computing. [ABSTRACT FROM AUTHOR]

The utilization of two-dimensional van der waals heterostructures in optoelectronic synapses allows for the integration of information processing and memory, thereby providing novel operating platforms for simulating the perceptual visual systems and developing the neuromorphic computing systems due to its contactless, highly efficient and parallel computing. Herein, we have constructed a straightforward MoS2/WS2 heterostructure optoelectronic synapse and examined its capacity to imitate synaptic behaviors under optical stimulus. The MoS2/WS2 device demonstrated several synaptic functions, such as the excitatory postsynaptic current, short-term plasticity, long-term plasticity, pairs-pulse facilitation and 'learning-experience' behavior. Moreover, the MoS2/WS2 synaptic device can achieve a wide range of photo response wavelengths, spanning from UV to visible light, as well as the conversion from short-term plasticity to long-term plasticity. Furthermore, light-induced charge transfer due to adsorption and desorption of oxygen molecules in MoS2/WS2 heterostructure can be used to explain its working mechanism. Additionally, the synaptic plasticity of MoS2/WS2 device can be controlled by adjusting the duration, power and number of the optical pulses, which renders the MoS2/WS2-based optoelectronic synaptic device extremely favorable for implementation in the perceptual visual system. [ABSTRACT FROM AUTHOR]

Etching plays a key role in processing and manufacturing electronic and optoelectronic devices. For ultra-wide bandgap semiconductor gallium oxide (Ga2O3), its etching investigations and evolution mechanism are still at the earlier stage, and some more research gumption should be invested. In this review, we make a summary on the etching of Ga2O3, including dry (plasma) etching, wet chemical etching, and photoelectrochemical etching, and discuss the etching results, existing problems, and feasible solutions, in order to provide guidance and advises for furtherly developing the Ga2O3 etching and Ga2O3-based electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, four original ternary neodymium complexes, [Nd(hth)3(L)x] (where x = 1 or 2; hth = 4,4,5,5,6,6,6-heptafluoro-1-(2-thienyl)-1,3-hexanedione and L = 1,10-phenanthroline (phen, 1), 5-bromo-1,10-phenanthroline (Brphen, 2), 5-chloro-1,10-phenanthroline (Clphen, 3), and triphenylphosphine oxide (tppo, 4), are reported. The complexes are synthesised by a two-step method and characterized thoroughly. The single crystal X-ray diffraction (SC-XRD) analysis is performed only for complex 4 due to the good quality of its crystals. The SC-XRD analysis indicates that complex 4 possesses an eight-coordinate structure in the solid state, having three hth and two tppo ligands. The 1H NMR analysis indicates that complexes 1–4 exhibit nine-coordinate structures in solution, having one coordinated water molecule besides hth and ancillary ligands. The Sparkle/PM7 optimized structures of the complexes are also presented, and complex 4 is compared with its crystal structure. Shape analyses reveal that complexes 1, 2, and 3 adopt biaugmented trigonal prism geometry, while complex 4 exhibits biaugmented trigonal prism J50 geometry. The photophysical investigations of the complexes were conducted in both solution and PMMA films in the near infrared (NIR) region. The results show that the hth ligand serves as an effective sensitizer and phen is the best antenna ligand. The TGA/DTA analysis indicates that the complexes are stable up to ∼200 °C, indicating their possible use in optoelectronic devices. Therefore, complex 4 is used as an emitting layer in a NIR-organic light-emitting device (OLED) with the following structure: ITO/MoO3 (2 nm)/β-NPB (30 nm)/TcTa:[complex 4] (20 nm, 10 wt%)/TPBi:[complex 4] (10 nm, 10 wt%)/TPBi (25 nm)/LiF (0.1 nm)/Al (100 nm). [ABSTRACT FROM AUTHOR]

Bismuth-based semiconductor materials have garnered significant attention because of their appropriate optical bandgap and substantial photoelectric conversion efficiency. Enhancing the photocurrent and fill factor of photovoltaic films is essential for developing high-performance optoelectronic devices. In this study, high-performance BiVO 4 -ZnTiO 3 multilayer films were fabricated using a straightforward sol-gel method, where the incorporation of ZnTiO 3 films significantly improved the photovoltaic performance of BiVO 4. Through structural design aimed at enhancing light utilization, the BiVO 4 -ZnTiO 3 multilayer film achieved a photocurrent density of 1.9 mA/cm2 at 450 nm, along with a fill factor of 46.8 % in the composite multilayer structure. The improvement in film performance is attributed to the overall multilayer stacking effect. This study offers a novel approach for utilizing bismuth-based semiconductors in optoelectronics. [ABSTRACT FROM AUTHOR]

Cu:CsPbClxBr3‐x quantum dots (QDs) with different Cu‐to‐Pb molar ratios were synthesized via a solvent‐based thermal synthesis method, and highly stable blue‐light PCL@Cu:CsPbClxBr3‐x composite fibers (CFs) were prepared by electrohydrodynamic (EHD) technology. The photoluminescence (PL) properties of these Cu2+‐doped Cu:CsPbClxBr3‐x QDs and the stability of polymer encapsulation were investigated in this study. The results showed that with increasing Cu2+ concentration, the CsPbCl1.5Br1.5 QDs maintained their initial cubic crystal structure. The doping of Cu2+ ions effectively eliminated the surface defects of CsPbCl1.5Br1.5 QDs, facilitating excitonic recombination through radiative pathways. The PL quantum yield (PLQY) of Cu:CsPbCl1.5Br1.5 QDs increased to 85%. In addition, The fiber encapsulation method effectively improved the stability of the Cu:CsPbCl1.5Br1.5 QDs, After 3 days in water, the fluorescence intensity still remains at the initial 90%. Based on these results, it is believed that Cu:CsPbCl1.5Br1.5 QDs have promising applications in optoelectronic devices in the future. [ABSTRACT FROM AUTHOR]

Utilizing the Cambridge Serial Total Energy Package (CASTEP), we examined various properties of the compounds Na X H 3 and K X H 3 (where X represents Tc, Ru and Rh). These properties include structural, thermodynamic, hydrogen storage, optical, mechanical, and electronic. The studied compounds exhibit stables cubic crystal structures with lattice constants between 3.53 Å and 3.77 Å. Their mechanical and thermodynamic stability is confirmed by their elastic constants, phonon dispersion, and negative formation energies. The gravimetric hydrogen storage capacities are 2.44, 2.38, 2.35, 2.16, 2.11 and 2.08 wt percent for NaTcH 3 , NaRuH 3 , NaRhH 3 , KTcH 3 , KRuH 3 and KRhH 3 , respectively. Notably, KTcH 3 has the most practical hydrogen desorption temperature of 365 K. Electronic properties reveal a consistent metallic behavior across all compounds, opening possibilities for applications beyond hydrogen storage. Their calculated optical properties, including conductivity, absorption, and refractive index, suggest that KTcH 3 may be suitable for use in optoelectronic devices and solar cells. Mechanical analysis highlights NaRuH 3 as the hardest material, based on the investigated elastic moduli. These findings underscore the potential of sodium- and potassium-based perovskite hydrides not only for hydrogen storage but also for advanced energy systems, electronics, and optics. • The properties of Na X H 3 and K X H 3 (X = Tc, Ru, Rh) are examined using DFT. • Na X H 3 and K X H 3 are found to be mechanically and thermodynamically stable. • All compounds showed stable cubic structures. • The electronic assessment showed that all hydrides are metallic. • The highest hydrogen capacity is observed in NaTcH 3 with a value of 2.44 wt%. [ABSTRACT FROM AUTHOR]

Although enhanced performance of photovoltaic devices by embedding metal nanoparticles in charge transport layer, doping into active layer bulk, decorating the active layer surface, and inserting at the interface between semiconductor and the electrode were reported, the effect of incorporating metal NPs at the interface of single crystal semiconductor and perovskite is rarely tackled. Herein the effects of incorporating Ag nanoparticals (AgNPs) at p-Si/MAPbI3 perovskite interface on the photodiode performance were investigated. The results showed that compared with the reference device (without AgNPs) the photoresponsivity of the device incorporating AgNPs is greatly improved with the exception of light with wavelengths falling in the spectral range where AgNPs have strong optical absorption. This effect is extremely significant for relatively shorter wavelengths in the visible region, and a maximal improvement of around 10.6 times in photoresponsivity was achieved. The physical origin of the exception for spectral range that AgNPs have strong optical absorption is the cancelation of scatter resulted enhancement through AgNPs by band-to-band absorption resulted reduction of photocurrent, in which the generated electron has energy near the fermi level and the hole has large effective mass, which relax by nonradiative recombination, thus making not contribution to the photocurrent. More importantly, the AgNP decorated device showed much faster photo response speed than the reference device, and a maximal improvement of around 7.9 times in rise and fall time was achieved. These findings provide a novel approach for high responsive and high speed detection for weak light. [ABSTRACT FROM AUTHOR]

A novel Schiff base (BSSMO) and its copper complex have been synthesized, and their structure was delineated using single crystal XRD studies. Computational techniques were used to design and evaluate BSSMO‐based luminophores, revealing a significant intramolecular hydrogen bond within the molecule. Understanding ESIPT is crucial for optimizing photophysical and luminophore properties of organic molecules, especially for advancing optoelectronic devices. The study also explored the mechanisms of GSIPT and ESIPT for these BSSMO‐based luminophores using transition state theory, charge distribution, molecular orbital analysis, and quantum theory of atoms in molecules. Results advocated that BSSMO‐L2 exhibits higher absorption compared with BSSMO‐L1 and the same trend is observed in emission spectral studies. However, the intensity of enol emissions in BSSMO‐L2 is lower than that of keto (BSSMO‐L3) emissions and the S1 (Keto form) emission of BSSMO‐L3 shows significantly larger values, making it attractive for optoelectronic devices. The findings offer valuable insights for the development of ESIPT emitters with distinct photophysical properties. The in silico antidiabetic study of BSSMO‐L2 explores the interaction with PPAR‐γ protein, revealing a moderate affinity and stable complex, enhancing its bio‐potential for future applications. The in vitro anticancer study of Cu‐BSSMO‐L2 complex shows a potential anticancer effect through mitochondrial and extrinsic death receptor mediated pathways. These insights contribute to the design of novel benzenesulfonamide‐based bioactive molecules. [ABSTRACT FROM AUTHOR]

Bi‐based organic halides have attracted widespread attention as potential substitutes for lead‐based organic halide perovskites and have been explored and applied in many optoelectronic devices. The rational design of organic Bi‐based halides is a popular research topic. In this work, we used benzylammonium (BA) cations to synthesize BA3Bi2I9 (BBI) perovskite material and FA3Bi2I9 (FBI, FA [formamidinium]) as control. We observe that the benzene rings in BA cations overlap with each other due to the benzene rings Π‐Π conjugation in the crystal structure of BBI, which exhibits large interplanar spacing due to large BA ions. BBI has preferential orientation along the (020) crystal plane. Due to conjugation, scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) mapping images indicate that the surface of the BBI thin film is smoother and more uniform than that of the FBI thin film. We fabricated the device by growing thin films of BBI and FBI on ITO interdigital electrodes. The photodetector based on BBI SC exhibits stability and regularity with turning on/off of the light at different intensities (10, 20, 30, and 40 W m−2) and wavelengths (386, 397, 405, and 433 nm). The ultraviolet–visible (UV–vis) absorption and reflection spectrum analysis shows that BBI has a slightly wider bandgap than FBI. This study can provide some ideas for the design Π‐Π conjugation in organic metal halides. [ABSTRACT FROM AUTHOR]

The flourishing environmental concerns have grabbed the attention of researchers developing environmentally supportive materials in various fields. A green approach was used to create biopolymer blend composites based on polyvinyl alcohol (PVA) and chitosan (CS) doped with various concentrations of grape seed (GS). Various analytical techniques, such as Fourier-transform infrared spectroscopy (FTIR), UV–visible (UV) spectra, field emission scanning electron microscope (FE-SEM) and differential scanning calorimetry (DSC) were used to evaluate the optical, structural and thermal properties of the prepared blend composites. The optical properties of blend composites were determined by UV spectroscopy and the findings revealed that absorption intensity increased with increasing GS, while bandgap energy decreased from 4.18 eV for pure blend to 2.91 eV for blend/15 wt% GS. The homogeneous distribution of GS particles in the biopolymer blend was identified with FE-SEM images. DSC results showed that increasing the GS content increased the glass transition temperature of the blend composites. The AC conductivity and dielectric constant were measured using the LCR meter. The conductivity rises with increasing frequency and dosage of GS, with the greatest conductivity obtained at 15 wt% loading. In comparison to a pure blend, it was discovered that the inclusion of 15 wt% GS enhanced the tensile strength by 50%, hardness by 17% and the reduction in elongation at break by 19 %. As a consequence, environmentally friendly PVA/CS/GS biopolymer blend composites with excellent mechanical, thermal, electrical, and dielectric parameters might be a viable green option for flexible electronic, electrochemical and energy storage devices. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Optical controlling of solid‐sate electric properties is emerging as a non‐contact and nondestructive avenue to optimize the physical properties of electronic and optoelectronic devices. In term of strong light‐material coupling, two‐dimensional (2D) double perovskites hold great prospects to create photo‐dielectric activities for high‐performance device applications. Here, we have achieved the photo‐excited switching and enhancement of dielectric properties in the orientational thin films of a 2D double perovskite, (C4H12N)4AgBiI8 (1, where C4H9NH3+ is isobutylammonium). It undergoes a structural phase transition at 384 K (Tc), triggered by the dynamic ordering of organic cations and tilting motion of isometallic perovskite sheets. Most notably, the orientational thin films of 1 are extremely sensitive to light illumination, of which the dielectric constants can be facilely photo‐switched between the low‐ and high‐states. During this photo‐switching process, the dielectric constants are enhanced with a magnitude up to ~350% under 405 nm, far beyond most of the inorganic phase transition counterparts. In addition, this photo‐excited switching and enhancement of dielectric response exhibits an operational stability with superior anti‐fatigue characteristics. Our work opens up a potential avenue for assembling high‐performance optoelectronic devices with the controllable physical properties. [ABSTRACT FROM AUTHOR]

The covellite phase of copper sulfide thin film (CuS), due to its excellent electronic, optical and chemical properties, has attracted enormous attention in cutting-edge research. This is a comprehensive study of the structural, optical, morphological and electrical properties of CuS thin films deposited by chemical bath deposition technique on flexible polyethylene terephthalate (PET) substrates at different deposition temperatures, i.e. 25 °C, 40 °C, 55 °C and 70 °C for the fabrication of flexible photodetectors. X-ray diffraction and Raman spectral studies reveal the presence of hexagonal covellite phase (CuS), whereas the root mean square (RMS) roughness of CuS thin film increases with an increase in deposition temperature. The optical bandgap of CuS thin film is found to be decreased with an increase in deposition temperature. The optimized CuS thin film, deposited at 70 °C, exhibits a homogeneous surface with RMS roughness of 13.72 nm, mobility of 25.09 cm2 V−1s−1 and bandgap of 1.86 eV. The mobility of CuS thin film is found to be increased with the increase in deposition temperature. The flexible CuS photodetector, fabricated at 70 °C, exhibits better photoresponse characteristics, with the highest responsivity of 0.18 mA W−1, specific detectivity of 1.39 × 108 Jones and sensitivity of 173.25 % upon light illumination. The established photocurrent possesses an outstanding dependence on various intensities of illuminated light. Furthermore, the bending test of flexible CuS photodetectors reveals the absence of any sign of deterioration up to bending angle of 30°. This suggests that the Al/CuS-PET/Al photodetector device could be used in various wearable optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Barium strontium titanate (BST) is a perovskite material, which is used directly in various applications including thermistors, electromechanical actuators, sensors and ceramic capacitors. Here, we have investigated the impact of dopant (Mn and Co) on synthesized BST nanoparticles and its morphological, structural, vibrational and optical properties have been investigated through scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), FTIR and Raman spectroscopies. SEM image showed the nearly spherical grain for pure BST and doped (Mn and Co) BST samples. The estimated particles were strongly influenced by different dopants, in addition, Mn-doped BST showed maximum grain growth for pure and Co-doped BST samples. XRD patterns have been employed to investigate the microstructural parameters (phase, lattice, crystallite size, strain, dislocation density, etc.). The crystallite sizes have been estimated using the Scherrer formula, showing maximum crystallite size for Mn-doped BST ceramics. Recorded FTIR spectra showed the transmission peak, which is centred at wavenumber of 470 cm−1 (pure BST), was shifted to 1250 cm−1 with Mn-doped BST. Raman spectra exhibited the increased number of modes from pure BST to Mn-doped BST sample. PL showed the emissions bands, which were observed at 602–659 nm. Here, the peak shifted towards higher wavelength from pure BST to Mn-doped BST (red shifting from pure to Mn-doped BST). It revealed that the prepared samples can be employed as suitable photoluminar material. [ABSTRACT FROM AUTHOR]

Owing to the increasing demands of high-density data storage double-halide perovskite-based resistive random access memory (RRAM) have recently emerged as a promising candidate in the forefront of next-generation optoelectronic memory applications. The ionic motion-based quick switching is the key feature of this kind of material, which plays a significant role in resistive switching (RS) applications. Recently, lead-free tin-based double-halide perovskites have been considered as favourable material due to their superior stability, functionality and eco-friendly nature. Here, we report the synthesis of cesium tin (IV) iodide (Cs2SnI6) perovskites. X-ray diffraction (XRD) pattern of the as-synthesized perovskite confirms the formation of Cs2SnI6 material. The crystallographic data corroborate the formation of a pure cubic phase, free of any other phase at room temperature. We also studied optical properties of the sample by using the ultraviolet–visible (UV) spectra and photoluminescence (PL) spectra. A broadband at around 580 nm is observed in the UV−Vis absorption spectra. The optical band gap of the sample is found to be 1.68 eV. Cs2SnI6 perovskite exhibited intense PL emission at ~540 nm. In this work, to fabricate a flexible Al/Cs2SnI6/ITO-PET memory device, we used Cs2SnI6 film as a switching layer and the device exhibits bipolar RS characteristics. [ABSTRACT FROM AUTHOR]

Since the discovery of lasers, high-quality nonlinear optical (NLO) single crystals have served as the foundation for the creation of novel, cutting-edge devices that meet societal demands. Modern optoelectronic applications such as telecommunication lasers, optical fibers, photodiodes, solar cells, etc. favor high-performance nonlinear optical single crystals with improved optical nonlinearity. Organic crystals are extensively explored for these applications because of their high NLO coefficient. This paper deals with the problems and advancements of organic nonlinear optical single crystals. Here, we review the growth and characterizations of various tosylate family crystals from the vast realm of organic single crystals and their potential applications in the field of optoelectronic devices. Various properties like linear and nonlinear optical, thermal, mechanical, and laser damage threshold values for these samples have been summarized. The attempts are made for highlighting how these tosylate (p-Toluenesulfonic acid based) family crystals can be realized into efficient optoelectronic devices by summarizing variously reported cut-off wavelengths and their wide transmission ranges. [ABSTRACT FROM AUTHOR]