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Zinc phosphide, Zn3P2, is a semiconductor with a high absorption coefficient in the spectral range relevant for single junction photovoltaic applications. It is made of elements abundant in the Earth's crust, opening up a pathway for large deployment of solar cell alternatives to the silicon market. Here we provide a thorough study of the optical properties of single crystalline Zn3P2thin films grown on (100) InP by molecular beam epitaxy. The films are slightly phosphorus-rich as determined by Rutherford backscattering. We elucidate two main radiative recombination pathways: one transition at approximately 1.52 eV attributed to zone-center band-to-band electronic transitions; and a lower-energy transition observed at 1.3 eV to 1.4 eV attributed to a defect band or band tail related recombination mechanisms. We believe phosphorus interstitials are likely at the origin of this band.

Researchers have found various families of two-dimensional (2D) materials and associated heterostructures through detailed theoretical work and experimental efforts. Such primitive studies provide a framework to investigate novel physical/chemical characteristics and technological aspects from micro to nano and pico scale. Two-dimensional van der Waals (vdW) materials and their heterostructures can be obtained to enable high-frequency broadband through a sophisticated combination of stacking order, orientation, and interlayer interactions. These heterostructures have been the focus of much recent research due to their potential applications in optoelectronics. Growing the layers of one kind of 2D material over the other, controlling absorption spectra via external bias, and external doping proposes an additional degree of freedom to modulate the properties of such materials. This mini review focuses on current state-of-the-art material design, manufacturing techniques, and strategies to design novel heterostructures. In addition to a discussion of fabrication techniques, it includes a comprehensive analysis of the electrical and optical properties of vdW heterostructures (vdWHs), particularly emphasizing the energy-band alignment. In the following sections, we discuss specific optoelectronic devices, such as light-emitting diodes (LEDs), photovoltaics, acoustic cavities, and biomedical photodetectors. Furthermore, this also includes a discussion of four different 2D-based photodetector configurations according to their stacking order. Moreover, we discuss the challenges that remain to be addressed in order to realize the full potential of these materials for optoelectronics applications. Finally, as future perspectives, we present some key directions and express our subjective assessment of upcoming trends in the field.

EPSRC DTP; Department of Mechanical and Aerospace Engineering, Brunel University London.

Exploring mmWave frequencies and adopting small-cell architectures are two key enablers for increased wireless data rates. To make these evolutions economically viable, centralized architectures based on radio-over-fiber (RoF) are devised. To reduce the complexity of the cellular network even further, RF-over-Fiber transmission schemes are adopted in combination with reflective uplink operation. This paper relies on a very low complexity narrowband GaAs electronics / Si photonics transceiver for scalable RFoF architectures with which we demonstrate a fiber-wireless link capable of transmitting over 7 Gb/s in down- and uplink for a 2 km fiber and 5 m wireless link in the 28 GHz band. Furthermore, it is shown that Rayleigh degradation caused by reflective uplink operation can be avoided by using a coherent detection scheme.

The Biswapped-Torus is a recently reported optoelectronic node-symmetrical member of Biswapped-framework family. In this paper,optimized parallel approach is presented for prefix sum computation on [Formula: see text] Biswapped-Torus. The proposed parallel algorithm demands total 7[Formula: see text] electronic and three optical moves on odd network size or 7[Formula: see text] electronic and three optical moves on even network size. The algorithmic performance of the suggested parallel algorithm is also compared with the performances of recently reported optimal prefix sum algorithms on [Formula: see text] Biswapped-Mesh and [Formula: see text]-dimensional Biswapped Hyper Hexa-cell. Based on the comparative analysis, Biswapped-Torus claims to map prefix sum faster that require fewer communication moves compared to the Grid-based traditional architecture of biswapped family named Biswapped-Mesh. Moreover, the former also has architectural benefit of node-symmetry that leads to advantages such as easy embedding, mapping and designing of routing algorithms. Compared to symmetrical counter-part of biswapped family named Biswapped-Hyper Hexa-Cell, Biswapped-Torus is cost-efficient, but requires comparatively more communication moves for mapping prefix sum.

Controlling the spectral tunability and isomerization activity is currently one of the hot topics in the design of photoreversible molecular switches for application in optoelectronic devices. The present work demonstrates how to manipulate the absorption of the retinal protonated Schiff base (rPSB) chromophore over the entire visible range by targeted functionalization of the retinal backbone. Moreover, a correlation between the vertical excitation energy and the profile of the potential energy surface of the bright excited state responsible for the photoreactivity of rPSB is established. This correlation was exploited to rank the functionalized rPSBs into different classes with characteristic photoisomerization activity. Eventually, the synergic effects of functionalization and of external electric fields in the range of a few MV cm−1 were applied to achieve reversable and regioselective control of the photoisomerization propensity of selected rPBS derivatives.

In comparison with the stoichiometry and Zn-rich/Cu-poor compositions of Cu2ZnSnS4 (CZTS) photovoltaic material, the properties of Cu-poor films have not been explored adequately. In this study, Cu-poor films were spin-coated from a non-hazardous methanol-based solution. Films were subject to a brief annealing process in the temperature range of 350–550 °C. As-grown and annealed films were uniform, compact, photosensitive, and free from secondary phases. As the annealing temperature increased, the size of crystallites increased and the film dislocation density decreased steadily. Films had a direct bandgap of 1.4–1.5 eV. The presence of three sub-bandgap transitions were detected and identified. By varying the annealing temperature, hole concentration, hole mobility, and film resistivity varied systematically in the range of 1016–1018 cm−3, 1–140 cm2/V-s, and 0.02–64 Ωcm, respectively. Cu-poor films showed structural and optoelectronic properties similar to the Zn-rich/Cu-poor and stoichiometric films and, thus, have the potential for device applications.

Migrating toward higher frequencies and densification of the communication cells are two key enablers for increased wireless data rates. To make these trends economically viable, centralized architectures based on radio-over-fiber (RoF) are explored. This article describes the design of a photoreceiver that can be applied at the remote radio head in a 28 GHz analog RoF link. The devised photoreceiver comprises a Ge-on-Si photodetector and co-designed GaAs low noise amplifier offering 24 dB gain, corresponding to 224 V/W external conversion gain, over a 3-dB bandwidth between 23.5 and 31.5 GHz. The associated noise figure is 2.1 dB and an output referred third order intercept point up to 26.5 dBm can be obtained with a power consumption of 303 mW. Two possible applications are demonstrated in this article. First, the photoreceiver is tested in a 5G New Radio environment resulting in rms-EVM values below 2.46/3.47% for 100/400-MBaud 16-QAM transmission over the 24.25-29.5 GHz band. Secondly, very high data rates can also be supported, demonstrated by a 36 Gb/s link with an rms-EVM of 5.2%.

In contrast to pressure distributions that can, nowadays, easily be measured using commercial sensor sheets, this is not yet the case for frictional or shear stresses. Those stresses act parallel to a surface, which makes it more challenging to develop suitable sensors. A number of shear sensor prototypes have been reported until now, but realizing a matrix of shear sensors remains a big challenge because of cost and complexity issues. Therefore, this article presents a fabrication approach for realizing a matrix of shear sensors using standard PCB and molding technologies. The presented sensor is based on changing the coupling of optical power between a light-emitting diode and a set of photodiodes in combination with an overmolding step, as realizing a mechanical transducer. To demonstrate the fabrication flow, a first demonstrator incorporating a five-taxel sensor matrix has been realized, which is able to record the in-plane shear stress magnitude and direction.

International audience; AbstractThe present study reports the impact of structural parameters on optoelectronic properties of InGasb/GaSb based quantum well structures (Qws). The laser diodes are designed to operate at 2.3 μm at 300 K. Numerical calculations of the emission wavelength, optical and modal gain of TE mode in InGaSb/GaSb laser diode structure have been carried out for various well material compositions, well thickness, number of quantum wells and temperature. The optical confinement factor and threshold current density are also simulated and reported. The calculations were performed using the 8-bands k.p model. For an injected carrier concentration of 1.56 × 1018 cm−3 at 300 K, peak gain value of the order of 1400 cm−1 is reached and a modal gain of 94 cm−1 can be obtained. A threshold current density around 3 kA/cm2, is expected to be obtained through optical losses of about 50 cm−1. The results show that InGaSb/GaSb quantum wells are appropriate for mid-infrared lasers operating at 300 K.

Successful adoption of defect management and carrier confinement strategies in Ruddlesden-Popper (RP) perovskites has driven the impressive improvements to performance of perovskite-based light-emitting diodes (PeLEDs) seen to date. Although functional additives have been advantageous in mitigating defects, their influence over crystallization behavior of RP (L2Am-1PbmX3m+1) perovskites has yet to be fully studied. This is especially important for blue-emitting mono-halide RP perovskites, where stringent control over m domain distribution is needed for efficient PeLEDs. Herein, we investigate the effect of tri-phenyl-phosphine-oxide (TPPO) on crystallization behaviour of blue RP (PBA2Csm-1PbmBr3m+1) perovskites. Despite TPPO addition, its absence in the resulting film eliminates its role as a passivating agent. Instead, TPPO acts as crystallization and phase distribution modulator – promoting the formation of a narrow distribution of higher m domains with higher Br content. In doing so, an enhancement of ~35% was noted with champion device yielding efficiency of 3.8% at λ of 483 nm. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version This research was funded by Ministry of Education, Singapore (MOE2018-T2-2-083) and (MOE2019-T2-2-097). The photophysical measurements are made possible through the support from the Ministry of Education, Singapore under its AcRF Tier 2 grant MOE-T2EP50120-0004, and the National Research Foundation, Singapore under its NRF Investigatorship (NRF-NRFI2018-04). We acknowledge the Facility for Analysis, Characterization, Testing and Simulation, Nanyang Technological University, Singapore, for use of their electron microscopy/X-ray facilities.

International audience; Solar energy-harvesting materials have significantly contributed to the development of energy-saving applications for several decades. We have mainly used a new concept composed of the electrophoretic deposition technique and photonic crystal structural engineering to understand the tunable light-absorption and electronic conduction properties. A hexamolybdenum cluster compound (denoted as the Mo6 cluster) was successfully functionalized on a tin pyrophosphate semiconductor integrated within an inverse opal photonic crystal. The size of the periodical pores, surface modification, and chemical composition of the infiltration material of the inverse opal film have been investigated to control the photonic bandgap in the visible range and the efficiency of the deposited Mo6 cluster. The photoactive Mo6 clusters act as a visible light harvester and generate an efficient photo-induced current upon light absorption that is enhanced by a slow photon effect occurring at the photonic stopband edges. The electron and proton are transferred in the inorganic-organic network via hydrogen bonds by a hopping mechanism to generate a rapid photoconductivity response during light irradiation. Specific attention focused on the role of humidity and temperature regarding the reproducibility of the experiments and the photosensitivity of the nanocomposite. The suitable tunable photo-induced conduction property in organic-inorganic materials opens a new opportunity for the applicability of cluster-based compounds in visible optoelectronic devices.

The structures of four phospho­rescent monoiridium and chloro-, cyanato- or oxamidato-bridged diiridium complexes with a potential for OLED applications are described., The crystal structures of tris­[9,9-dihexyl-2-(5-meth­oxy­pyridin-2-yl-κN)-9H-fluoren-3-yl-κC 3]iridium pentane monosolvate, [Ir(C31H38NO)3]·C5H12, (I), di-μ2-chlorido-bis­{bis­[2-(5-fluoro­pyridin-2-yl)-9,9-dihexyl-9H-fluoren-3-yl]iridium} pentane 0.3-solvate, [Ir2(C30H35FN)4Cl2]·0.3C5H12, (II), di-μ2-cyanato-bis­{bis­[9,9-dihexyl-2-(5-meth­oxy­pyridin-2-yl)-9H-fluoren-1-yl]iridium} pentane monosolvate, [Ir2(C31H38NO)4(NCO)2(NCO)2]·C5H12, (III), and {μ-N,N′-bis­[3,5-bis­(tri­fluoro­meth­yl)phen­yl]oxamidato}bis(bis{2-[4-(2,4,6-trimethylphenyl)pyridin-2-yl]phenyl-κ2 C 1,N′}iridium)–chloro­benzene–pentane (1/2.3/0.4), [Ir2(C20H19N)4(C18H6F12N2O2)]·2.3C6H5Cl·0.4C5H12, (IV), synthesized in the quest for organic light-emitting devices, were determined. The bis-μ2-chloro and bis-μ2-cyanato complexes have ΔΔ and ΛΛ configurations of the distorted octa­hedral Ir centres in racemic crystals, whereas the oxamido complex has a centrosymmetric (meso) structure with the ΔΛ configuration. The bridging oxamido moiety has a nearly planar anti geometry. All structures show substantial disorder of both host mol­ecules and solvents of crystallization.

In recent years, metal halide perovskite nanocrystals (NCs) have been favored by many researchers due to their unique properties including long carrier diffusion length, high carrier mobility, tunable emission wavelength, and narrow full width at half maximum, making them great application potentials in optoelectronic devices. The photoluminescence quantum yields of perovskite NCs are nearly 100%, and the device efficiency of perovskite NC‐based light‐emitting diodes (LEDs) has been improved significantly from below 0.1% to over 20%. In addition, perovskite NC‐based solar cells and photodetectors have also developed rapidly in recent years. Here, we summarize the synthesis and the basic optoelectronic properties of metal halide perovskite NCs and introduce their applications in LEDs, solar cells, and photodetectors.

The aim of this study is to investigate the influences of annealing temperature on initial device characteristics and their correlations with ultraviolet (UV) radiation sensitivity of n-type zinc oxide/p-silicon (n-ZnO/p-Si) heterojunction photodiodes. Evolutions on the crystalline structure, surface morphology, ideality factor, barrier potential, interface state density, and donor concentration were systematically analyzed during the initial device characterizations before testing the UV sensitivities of the photonic devices. The results demonstrate that the sensitivity of each n-ZnO/p-Si photodiode annealed at various temperatures was linearly correlated with different UV illumination intensities. The devices annealed at 750 ºC and 550 ºC exhibit more sensitive performance than devices annealed at 150 ºC and 350 ºC owing to lower dark currents and good oxide quality. However, the presence of an interfacial suboxide or silicate oxide layer significantly decreased the responsivity of the photodiodes annealed at 750 ºC. The maximum responsivity value was 126 mA/W for the photodiode annealed at 550 ºC. It can be concluded that the photodiode annealed at 550 ºC exhibits promising performance for UV sensing applications.

International audience; In order to improve the solar cell efficiency, quantum multi-wells have been implanted into the intrinsic region of the structure. We can absorb the photons that have a lower energy than the bandgap energy. In this work, physical and optical phenomena that influence the efficiency of the solar cell have been modeled, simulated and optimized. In addition, the effects of indium (x) and nitrogen (N) concentrations, the quantum wells number (nQWs) and the quantum well width (Lw) on structural stability, bandgap energy, external quantum efficiency and the solar cell output parameters were studied. For indium and nitrogen concentrations x = 35%, y = 3.5% respectively, a quantum well width LW = 8 nm and quantum wells number nQWs of 50, we have obtained a strain (ε) of about 1.77%. The obtained external quantum efficiency (EQE) in this case is about 86.23%, while the efficiency (η) is 33.60%. We can improve this work by using other materials.

Zinc oxide (ZnO) thin films are significant in various electronic applications. This study introduced an efficient, simple, low cost and timesaving method to obtain an extended and uniform ZnO thin film with tunable surface morphology over the substrate using the spin coating technique. Different concentrations of zinc acetate dehydrate were used as precursor solutions mixed with polyvinyl alcohol as a binding polymer to obtain the film’s uniformity and to relieve thermal expansion that may cause a wrinkled surface. Synthesized films were characterized using X-ray diffraction (XRD), X-ray spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and ellipsometry. Findings show that the average size of ZnO particles was less than 50 nm in a uniform film over the whole substrate area regardless of the presence or absence of wrinkles. Additionally, this method was quite fast, attaining the desired viscosity in less than one hour in comparison with the time-consuming aging method, which requires approximately 24 h to achieve the required viscosity.

Nanostructured ZnO has got a lot of interest as a suitable material for various applications especially sensing, energy conversion and storage. ZnO nanostructures can be synthesized in a number of ways. It is one of the materials that can be prepared in a variety of morphologies including hierarchical nanostructures. This review article presents a review of current research activities on growth of ZnO Nanorods. The article covers various water based routes of synthesis, and is further characterized by the type of substrate used for the growth. The growth factors involved in the hydrothermal and chemical bath deposition methods are discussed. These factors include the variety of precursors, time, temperature and the seeding method employed. At the end, applications such as gas sensing and improvement in opto-electric properties in relation to the morphology are discussed.

Thin films of transparent conductive Al doped ZnO (AZO) thin films were produced via sol-gel spin coating route. Structural, optical, and electrical properties were explored for several dopant concentrations. Formation of crystalline AZO was verified by X-ray Diffraction (XRD) Analysis and structural analysis were carried out later from the XRD data. Highest band gap of 3.67 eV was found for 2 mol % AZO thin films. The average transmittance was found to be 84.19% in the visible spectra for the corresponding thin films. 2 mol% AZO also exhibited a minimum resistivity of 2.05 Ω-cm with a maximum value of figure of merit. Prolonged UV irradiation was applied to 2 mol % AZO thin films prior to annealing. It significantly modified the surface morphology of the film and provided shielding near UVA (315–378 nm) spectrum. This also enhanced the conductivity of the thin film by 3-fold compared to non-UV treated sample and decreased optical band gap significantly., Thin film; Sol-gel; Optoelectronic; Burstein-moss effect; UV irradiation; UV blocking.

Polar semiconducting polymers based on a conjugated polymer backbone endowed with chemically anchored polar groups on the side chains have proved to be particularly interesting as optimization layer at organic/cathode interface in optoelectronic devices. In particular, the pendant phosphonate groups impart water-alcohol solubility allowing easy solution processing, and improve electron injection thanks to both a favorable interfacial dipole of phosphonate groups and an intense coordination interaction between the phosphonate groups and Al cathode. In this work we synthesize alternating fluorene-benzothiadiazole copolymers by proposing a post-polymerization reaction to insert the phosphonate groups. Thanks to this approach it is possible to use standard Suzuki coupling conditions, simplifying the process of synthesis, purification and characterization. The polymer Poly[9,9-bis(6′-diethoxylphosphorylhexyl)-alt-benzothiadiazole] (P2), is tested in conventional organic solar cells as cathode interfacial layers showing, with respect to the control device, an increasing of all the photovoltaic parameters, with a final power conversion efficiency that reaches 5.35% starting from 4.6%. The same trend is observed for multilayered polymer light-emitting diodes with an external quantum efficiency of the P2-based PLED enhanced of 1.5 times with respect to the basic devices with bare Al cathode, and negligible roll-off efficiency. The synergic effects of energy gap modulation and of polar phosphonated pendant functionalities of P2 are compared with the corresponding fluorene-based polar homopolymer. Our results show that, not only a proper selection of side functionalities, but also the tailoring of the energy gap of cathode interfacial materials (CIMs) is a possible effective strategy to engineer cathode of different optoelectronic devices and enhance their performance.

The development of organic light-emitting diodes (OLEDs) is very important due to their use in new generation lighting and displays, their color resolution and their unique optical properties. Herein, the change of the electronic and optical properties of a new molecule, 4-[(E)-[(2-hydroxy-1-naphthalenyl)methylene]amino]-3-methyl benzoic acid (HNMB) in different solvents are reported by experimental and advanced theoretical calculations. Optical properties are investigated by calculating the optical absorption wavelength, optical refractive index, optical band gap, optical conductance, angle of incidence, angle of refraction, contrast for different solvents. Finally, due to well-suited photonic and optoelectronic properties, the HNMB can be used as a phosphorescent and OLED material.

Ultraviolet-visible-near infrared broadband photodetectors have significant prospects in many fields such as image sensing, communication, chemical sensing, and day and nighttime surveillance. Hybrid one-dimensional (1D) and zero-dimensional (0D) materials are attractive for broadband-responsive photodetectors since its unique charges transfer characteristics and facile fabrication processes. Herein, a Si/ZnO nanowires/Ge quantum dots photodetector has been constructed via processes that combined electrospinning and spin-coating methods. A broadband response behavior from ultraviolet to near-infrared (from 250 to 1550 nm) is observed. The responsivity of the hybrid structure increases around three times from 550 to 1100 nm compared with the pure Si photodetector. Moreover, when the photodetector is illuminated by a light source exceeding 1100 nm, such as 1310 and 1550 nm, there is also a significant photoresponse. Additionally, the ZnO NWs/Ge quantum dots heterostructure is expected to be used in flexible substrates, which benefits from electrospinning and spin-coating processes. The strategy that combines 1D ZnO NWs and 0D solution-processed Ge QDs nanostructures may open a new avenue for flexible and broadband photodetector.

International audience; A series of N1,N4-didodecyl-N1,N4-diphenylbenzene-1,4-diamine based polysquaraines have been synthesized under micro-wave irradiation in the absence of any catalyst. The effect of solvent of polymerization, on the squaric acid catenation (1,2 and 1,3 linkages), has been studied and polysquaraines integrating linear chain in their backbone have been advantageously obtained by using di-functional alcohol during the polymerization. Such obtained polymers exhibit a broad emission with a quantum yield up to 18%. The latter were then tested into OLED devices exhibiting a promising white emission.

The effect of ethynylene spacers on the bandgap of alternating polymers, comprising 4,7-linked benzothiadiazole units and 2,7-linked fluorene, 2,7-linked carbazole or 2,6-linked anthracene repeat units has been investigated. The three novel polymers PFDEBT, PCDEBT and PPADEBT were prepared via the Sonogashira coupling reaction. The optical, electrochemical and thermal properties of the resulting polymers were compared and analysed. All polymers displayed low solubility in common organic solvents and have moderate molecular weights. Optical studies revealed that all the new ethynylene based-polymers displayed large bandgaps in excess of 2.1 eV. Results highlighted that incorporation of acetylene units between the benzothiadiazole electron accepting units and the other electron donor units over polymer chains leads to wide bandgaps as a result of the electron accepting properties of the acetylene units. The HOMO levels of the resulting polymers are unaffected by the different donor moieties used. However, varying the electron donor units can perturb the electron accepting ability of the main chain of polymers in this series and their LUMO levels. Anthracene-based polymer (PPADEBT) displayed the lowest LUMO level, while the fluorene-based polymer (PFDEBT) displayed the highest LUMO level. All polymers showed good stability to thermal degradation. The amorphous nature of these polymers was confirmed with powder X-ray diffraction studies.

In the present study, nickel-doped zinc oxide thin films (ZnO:Ni) at different percentages (0–10%) were deposited on glass substrates by using a chemical spray technique. The effect of Ni concentration on the structural and optical properties of the ZnO:Ni thin films was investigated. The effect of Ni contents on the crystalline structure and optical properties of the films was systematically investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), UV–vis, Photoluminescence spectra PL, and Raman spectrometry. The XRD analysis showed that both the undoped and Ni-doped ZnO films were crystallized in the hexagonal structure with a preferred orientation of the crystallites along the [002] direction perpendicular to the substrate. The XRD analysis also showed that the films were well crystallized in wurtzite phase with the crystallites preferentially oriented towards (002) direction parallel to the c-axis. SEM study reveals the surface of NiZnO to be made of nanocrystalline particles. The SEM images showed a relatively dense surface structure composed of crystallites in the spherical form whose average size decreases when the [Ni]/[Zn] ratio increases. The optical study showed that all the films were highly transparent. The band gap decreased up to the 7 at% Ni doping level, but the band gap increased after 10 at% Ni doping level. All thin films exhibited approximately 80% and above transmittance in the visible region. PL spectra of undoped and Ni-doped ZnO thin films showed some marked peaks at 376, 389, 494, and 515 nm. The obtained results revealed that the structures and optical properties of the films were greatly affected by doping levels. These films are useful as conducting layers in electro chromic and photovoltaic devices. Finally, all results were discussed in terms of the nickel doping concentration.

Performed in this work is a comprehensive theoretical computer analysis of performances inherent to two types of multichannel optical rotary connectors (ORC) of compensation operation based on mirror and prismatic compensators. This analysis relies on exact analytical expressions obtained for light ray paths in ORC models with a mirror compensator made in the form of bilateral mirror placed between two optical hemispheres and with prismatic compensator made in the form of Dove prism placed between two non-aberrational elliptic lenses. Found in ORC with the mirror compensator is the essential deficiency inherent to all these constructions, which is related with considerable rotary oscillations in the value of optical signals in mirror angular positions when the mirror halves the input light beam. In these mirror positions, the amplitude value of optical signal oscillations exceeds 95%, and optical losses are higher than –13 dB, when the rotor turns. One deficiency more in these constructions is also strict technical requirements to the accuracy of making the optical components and mechanisms at the level of 1…2 µm. Concerning the ORC construction with a prismatic compensator as well as collimator and focusing lenses common for all the channels, one should note the inadmissibly high optical losses of the signal value (higher than –30…40 dB) in the case of construction with fiber-optic interfaces, and large dimensions and mass in the case of active construction with optoelectronic transducers at the inputs and outputs of ORC. For example, when the number of channels N = 10 the longitudinal dimension of optical transfer channel (prism and lenses) exceeds 300 mm, and this dimension increases with increasing the number of channels. When this dimension is lower than 100 mm, the facility can be equipped with only one optical communication channel containing one LED and one photodiode located on the rotation axis. Optical losses in these constructions cannot be also considered as the satisfactory ones, since the respective loss value is higher than –18 dB for the number of channels N = 10.

Peptide self-assembly has attracted extensive interest in the field of eco-friendly optoelectronics and bioimaging due to its inherent biocompatibility, intrinsic fluorescence, and flexible modulation. However, the practical application of such materials was hindered by the relatively low quantum yield of such assemblies. Here, inspired by the molecular structure of BFPms1, we explored the "self-assembly locking strategy" to design and manipulate the assembly of metal-stabilized cyclic(l-histidine-d-histidine) into peptide material with the high-fluorescence efficiency. We used this bioorganic material as an emissive layer in photo- and electroluminescent prototypes, demonstrating the feasibility of utilizing self-assembling peptides to fabricate a biointegrated microchip that incorporates eco-friendly and tailored optoelectronic properties. We further employed a "self-encapsulation" strategy for constructing an advanced nanocarrier with integrated in situ monitoring. The strategy of the supramolecular capture of functional components exemplifies the use of bioinspired organic chemistry to provide frontiers of smart materials, potentially allowing a better interface between sustainable optoelectronics and biomedical applications.

Author(s): Nguyen, V; Gramling, H; Towle, C; Li, W; Lien, DH; Kim, H; Chrzan, DC; Javey, A; Xu, K; Ager, J; Taylor, H | Abstract: One of the major challenges in the van der Waals (vdW) integration of two-dimensional (2D) materials is achieving high-yield and high-throughput assembly of predefined sequences of monolayers into heterostructure arrays. Mechanical exfoliation has recently been studied as a promising technique to transfer monolayers from a multilayer source synthesized by other techniques, allowing the deposition of a wide variety of 2D materials without exposing the target substrate to harsh synthesis conditions. Although a variety of processes have been developed to exfoliate the 2D materials mechanically from the source and place them deterministically onto a target substrate, they can typically transfer only either a wafer-scale blanket or one small flake at a time with uncontrolled size and shape. Here, we present a method to assemble arrays of lithographically defined monolayer WS2 and MoS2 features from multilayer sources and directly transfer them in a deterministic manner onto target substrates. This exfoliate-align-release process - without the need of an intermediate carrier substrate - is enabled by combining a patterned, gold-mediated exfoliation technique with a new optically transparent, heat-releasable adhesive. WS2/MoS2 vdW heterostructure arrays produced by this method show the expected interlayer exciton between the monolayers. Light-emitting devices using WS2 monolayers were also demonstrated, proving the functionality of the fabricated materials. Our work demonstrates a significant step toward developing mechanical exfoliation as a scalable dry transfer technique for the manufacturing of functional, atomically thin materials.

Photovoltaic properties of solar cells based on fifteen organic dyes have been studied in this work. B3LYP/6-311G (d,p) methods are realized to obtain geometries and optimize the electronic properties, optical and photovoltaic parameters for some quinoxaline derivatives. The results showed that time dependent DFT investigations using the CAM-B3LYP method with the polarized split-valence 6-311G (d,p) basis sets and the polarizable continuum model PCM model were sensibly able to predict the excitation energies, the spectroscopy of the compounds. HOMO and LUMO energy levels of these molecules can make a positive impact on the process of electron injection and dye regeneration. Gaps energy ΔEg, short-circuit current density Jsc, light-harvesting efficiency LHE, injection driving force ΔGinject, total reorganization energy λtotal and open-circuit photovoltage Voc enable qualitative predictions about the reactivity of these dyes., Energy; Physics; Computing methodology; Theoretical computer science; Molecular physics; Particle physics; Quantum mechanics; TD-DFT; PCM; Quinoxaline derivatives; Solar cells; Optoelectronic; Photovoltaic.

Current-voltage characteristics of metal-protein-metal structures made of proteorhodopsin and bacteriorhodopsin are modeled by using a percolation-like approach. Starting from the tertiary structure pertaining to the single protein, an analogous resistance network is created. Charge transfer inside the network is described as a sequential tunneling mechanism and the current is calculated for each value of the given voltage. The theory is validated with available experiments, in dark and light. The role of the tertiary structure of the single protein and of the mechanisms responsible for the photo-activity is discussed.

International audience; A buried quad junction (BQJ) photodetector has been designed and fabricated with a high-voltage CMOS process. It implements four vertically-stacked p-n junctions with four different spectral responses. This feature allows high spectral discriminating ability, greater than both conventional buried double junction and buried triple junction detectors. In this paper, we propose a SPICE-like model, based on the physical properties of the device structure. The proposed model has been integrated in EDA software. It could be used for rapid and reliable design of system on chip, integrating the BQJ sensor, and its signal processing. The analytical expressions of the four BQJ photocurrents, as well as dark currents, have been developed. The spectral characteristics of the photodetector, computed with the proposed model, have been compared with those from TCAD simulations and experimental measurements. The analytical is close to the measurement with an average error on spectral responses in the range of 3-17 %, depending on the considered junction.

Conducting polymers have attracted tremendous attention because of their unique characteristics, such as metal-like conductivity, ionic conductivity, optical transparency, and mechanical flexibility. Texture and nanostructural engineering of conjugated conducting polymers provide an outstanding pathway to facilitate their adoption in a variety of technological applications, including energy storage and harvesting devices, flexible optoelectronic devices, and wearable electronic devices. Generally, obtaining high carrier mobility in the presence of high carrier density is challenging and requires precise control of the texture and nanostructure of conducting polymers to avoid the charge localization. Preferential semicrystalline orientation, π–π stacking distances, crystallite size, intra- and interchain couplings, intra- and intercrystallite connections, and grain boundaries are the key parameters that influence the charge carrier mobility and needs to be controlled by the synthesis parameters. This article provides a comprehensive overview of the recent texture and nanostructural engineering development of conducting polymers. In addition, this work describes the fundamental of charge carrier transport mechanisms in conducting polymers; and the latest progress on the optoelectronic characteristics of flexible transparent conductive electrodes based on conducting polymers is reported.

International audience; In this paper, we report a simulation and investigation of a single InxGa1-xN/GaN axial multiple quantum well nanowire (MQWNW) solar cell of radius r = 190 nm and a length of L = 1165 nm. Our results have been shown that 15 In0.15Ga0.85N (QW) /GaN (barrier) periods is the maximum number that our structure can be supported with an optimal efficiency of about 1.65% achieved with ε = 1.5%. The insertion of MQWs in nanowire permits the growth of InxGa1-xN MQWs with high indium concentration of about 50% and ε = 5%. At this indium concentration, the optimal efficiency obtained was 1.70%. Moreover; the structure has been studied with respect to the nanowire radius. In this context, we have shown that the efficiency enhancement achieved through the increase of radius is attributed to the increase of photo-carriers. Study of polarization and proton irradiations has indicated the negative effect of polarization on structure performances and high resistance of III-N semiconductor materials against the radiations, respectively. From these novel structures we can improve solar cell performance for new applications.

Золь-гелеву техніку застосовували для отримання тонких плівок чистого оксиду олова (SnO2). Плівки вирощували при кімнатній температурі на чистих скляних підкладках методом центрифугування. Дигідрат хлористого олова (II) використовували як вихідний матеріал, а 2-пропанол – як розчинник. Молярність олова зберігалася [Sn2+] = 0.3 M. На мікрофотографіях SEM опрацьованих плівок видно, що вони складаються із дуже дрібнозернистих частинок. XRD аналіз виявляє, що всі відпалені плівки складаються з однофазного SnO2, дифрактограми вказують на наявність піків (100), (101), (211), що відповідають тетрагональній фазі без будь-яких вторинних фаз. Зображення скануючої електронної мікроскопії та атомно-силової мікроскопії показують еволюцію різних поверхневих морфологій; усі плівки мають однорідну та рівномірну морфологію поверхні. Просвічуюча електронна мікроскопія підтверджує, що підготовлені плівки є нанокристалічними. Крім того, досліджується вплив багатошарового покриття на оптоелектронні властивості тонких плівок SnO2. У видимій області пропускна здатність перевищує 85 %. Питомий опір тонких плівок SnO2 значно зменшується з товщиною. Орієнтовне максимальне значення провідності становить 2.72 (Ω.см) – 1. Sol-gel technique was operated to obtain pure tin oxide (SnO2) thin films. The films were grown at room temperature on clean glass substrates by a spin coating method. Tin (II) chloride dehydrate was used as a starting material, and 2-propanol was used as the solvent. Tin molarity was kept [Sn2+] = 0.3 M. The SEM micrographs of the elaborated films show that they are composed of very fine-grained microstructure of SnO2. XRD analysis reveals that all annealed films consist of single phase SnO2, the diffractograms indicate the presence of (100), (101), (211) peaks corresponding to the tetragonal phase without any secondary phases. The scanning electron microscopy and the atomic force microscopy images show the evolution of the different surface morphologies; all films have homogeneous and uniform surface morphology. The transmission electron microscopy measurements confirm that the prepared films are nanocrystalline. Furthermore, the influence of multiple coating on the optoelectronic properties of SnO2 thin films is examined. In the visible region, the transmittance is greater than 85 %. The resistivity of SnO2 thin films decreases significantly with the thickness. The estimated maximum value of conductivity is 2.72 (Ω.cm) – 1.

Halide perovskites have emerged as a class of promising semiconductor materials owing to their remarkable optoelectronic properties exhibiting in solar cells, light-emitting diodes, semiconductor lasers, etc. Inorganic halide perovskites are attracting increasing attention because of the higher stability toward moisture, light, and heat as compared with their organic-inorganic hybrid counterparts. In particular, inorganic halide perovskite nanomaterials provide controllable morphology, tunable optoelectronic properties, and improved quantum efficiency. Here, the development controlled synthesis of desired inorganic halide perovskite nanostructures by various chemical approaches is described. Utilizing these nanostructures as platforms, anion exchange chemistry for wide compositional and optical tunabilities is described, and the rich structural phase transition phenomenon and mechanism investigated systematically. Furthermore, these nanostructures and extracted knowledge are applied to design photonic, photovoltaic, and thermoelectric devices. Finally, future directions and challenges toward improvement of the optical, electrical, and optoelectronic properties, exploration of the anion and cation exchange kinetics, and alleviation of the stability and toxicity issues in inorganic lead based halide perovskites are discussed to provide an outlook on this promising field.

The organization of nanowires on surfaces remains a major obstacle toward their large-scale integration into functional devices. Surface-material interactions have been used, with different materials and substrates, to guide horizontal nanowires during their growth into well-organized assemblies, but the only guided nanowire heterostructures reported so far are axial and not radial. Here, we demonstrate the guided growth of horizontal core-shell nanowires, specifically of ZnSe@ZnTe, with control over their crystal phase and crystallographic orientations. We exploit the directional control of the guided growth for the parallel production of multiple radial p-n heterojunctions and probe their optoelectronic properties. The devices exhibit a rectifying behavior with photovoltaic characteristics upon illumination. Guided nanowire heterostructures enable the bottom-up assembly of complex semiconductor structures with controlled electronic and optoelectronic properties.

Al-Sehemi, Abdullah/0000-0002-6793-3038; Ozdemir, Namik/0000-0003-3371-9874; gencer imer, arife/0000-0002-8147-9169 WOS: 000496810900026 Spin coated Cu(II) complex thin layer onto p-Si substrate was used in photodiode fabrication. The structural properties of novel synthesized Cu(II) complex were investigated using different techniques. The single crystal X-ray diffraction (sc-XRD) technique confirms the Cu(II) complex containing 2-mesityl1H-benzo[d]imidazole ligands and two chloride ligands have a highly distorted cis-square-planar geometry. The thermogravimetric analysis (TGA) shows that the Cu(II) complex is stable up to 248 degrees C. Also, the current-voltage measurements were performed to investigate the characteristic of photodiode based on copper complex in darkness and under solar simulator. The fundamental electrical parameters of fabricated diode were obtained using Thermionic theory and modified Norde function. The manufactured device exhibits a good response to light with the defined rise and fall time of 351 ms and 622 ms under 100 mWcm(-2) solar illumination, respectively. Furthermore, frequency dependent capacitance and conductance measurements were performed in dark and under illumination. The obtained results suggest that prepared photodiode based on Cu(II) complex could be used for organic light detection in different optoelectronic applications as photodetector, photocapacitor, and photoconductor. (C) 2019 Elsevier B.V. All rights reserved. Firat University Scientific Research Projects UnitFirat University [FF.18.29]; Research Center for Advanced Materials Science at King Khalid University [RCAMS/KKU/007-18] This study was supported by Firat University Scientific Research Projects Unit under project No: FF.18.29. Also, this research was supported by the Research Center for Advanced Materials Science at King Khalid University through a grant RCAMS/KKU/007-18. Authors want to acknowledge them for their support.

This work describes the implementation of a low-cost spectrometer produced with common objects and proposed as a pedagogical students' project. This task aims to introduce the theme of image detection and to stimulate the students to develop skills in the field of optics and photonics. The performance of the developed spectrometer was tested in the characterisation of several sources such as light emitting diodes (LEDs) operating in the visible spectral range and the results were compared with those obtained with a commercial spectrometer. Foreseeing a possible application, the spectrometer was used to calculate the emission ( x,y) colour coordinates following the Commission Internationale d'Eclairage (CIE) definition of the LEDs. The calculated ( x,y) colour coordinates using the built spectrometer compare well with those calculated using the emission data measured using a commercial spectrometer, pointing out that the proposed methodology provides good resolution and precision in the calculation of the CIE colour coordinates. This project was offered with success in 2010 to students from the Optoelectronics unit of the Physics Engineering Masters degree at Aveiro University, Portugal.

Large area, planar optronic systems based on flexible polymer substrates allow a reel-to-reel mass production, which is widely adopted in modern manufacturing. Polymer optronic systems are fully integrated with micro optical and optoelectronic components as light sources, detectors and sensors to establish highly functional sensor networks. To achieve economical production, low-cost polymer sheets are employed. Since they are mostly thermally sensitive, this requires a restricted thermal loading during processing. Furthermore, a short process time improves production efficiency, which plays a key role in manufacturing processes. Thus, in this contribution we introduce a new bare chip bonding technique using light instead of heat to meet both requirements. The technique is based on the conventional flip-chip die bonding process. Ultraviolet radiation curing adhesives are applied as bonding material, accordingly a sideway ultraviolet radiation source, a so-called optode, is designed. Before implementing the concept, the light distribution in the contact spot is simulated to examine the feasibility of the solution. Besides, we investigate two different UV lamps regarding induced thermal influence on polymer substrate to choose one to be employed in the optode. Process factors, irradiation intensity and irradiation time are studied. Based on these results, the mechanical and electrical reliability of the integrated components is finally evaluated.

Computational investigations of fused thiophenes including not only thienothiophene, ditihienothiophene and thienoacene but also other thiophene-fused (hetero)-aromatic rings have been surveyed. The effect of the methods and basis sets applied on promising optoelectronic materials were elaborated. This brief review suggests the best method for the fused thiophenes to be B3LYP functional. (C) 2016 ACG Publications. All rights reserved.

This work summarizes recent development in the filed of nanocrystal and their use for optoelectronics. After the introduction on nanocrystals and their transport properties, the manuscript is splitted in three parts : (i) narrow abnd gap materials, (ii) 2D colloidal material and (iii) van der waals heterostrctures, the perspective section has been intentionally removed

Graphene is emerging as a promising material for photonic applications owing to its unique optoelectronic properties. Graphene supports tunable, long-lived and extremely confined plasmons that have great potential for applications such as biosensing and optical communications. However, in order to excite plasmonic resonances in graphene, this material requires a high doping level, which is challenging to achieve without degrading carrier mobility and stability. Here, we demonstrate that the infrared plasmonic response of a graphene multilayer stack is analogous to that of a highly doped single layer of graphene, preserving mobility and supporting plasmonic resonances with higher oscillator strength than previously explored single-layer devices. Particularly, we find that the optically equivalent carrier density in multilayer graphene is larger than the sum of those in the individual layers. Furthermore, electrostatic biasing in multilayer graphene is enhanced with respect to single layer due to the redistribution of carriers over different layers, thus extending the spectral tuning range of the plasmonic structure. The superior effective doping and improved tunability of multilayer graphene stacks should enable a plethora of future infrared plasmonic devices with high optical performance and wide tunability.

Polycrystalline transparent Zinc oxide thin films have been grown on glass substrates by the sol–gel technique using two different precursor solutions. The physical properties of the films were analyzed with X-ray diffraction, Atomic Force Microscopy, UV–Vis and Raman spectroscopy. The results show that the films grew in the hexagonal wurtzite structure. The band gap of the samples was estimated from UV–Vis measurements in values from 3.1 to 3.22 eV, these values are in agreement with those reported in the literature. Two different simple ways to obtain polycrystalline ZnO were developed and the properties of the films were studied as a function of the precursor solution.

We investigate light emission from nanoscale point-sources obtained in hybrid metal-GaAs nanowires embedding two sharp axial Schottky barriers. Devices are obtained via the formation of Ni-rich metallic alloy regions in the nanostructure body thanks to a technique of controlled thermal annealing of Ni/Au electrodes. In agreement with recent findings, visible-light electroluminescence can be observed upon suitable voltage biasing of the junctions. We investigate the time-resolved emission properties of our devices and demonstrate an electrical modulation of light generation up to 1 GHz. We explore different drive configurations and discuss the intrinsic bottlenecks of the present device architecture. Our results demonstrate a novel technique for the realization of fast subwavelength light sources with possible applications in sensing and microscopy beyond the diffraction limit.

Tactile shear sensors gain importance for example in the field of robotics and biomedical sciences. For these applications, an “artificial skin”-like solution is needed with very thin and flexible unobtrusive sensors that can be wrapped around irregular surfaces or body parts. We present a tactile shear sensor based on the changing optical coupling between a light source (Vertical-Cavity Surface-Emitting Laser (VCSEL)) and a photodiode, separated by a transparent deformable transducer layer. When shear stress is applied onto the stack, both components move laterally and the photodiode captures a differing amount of light. Commercially available bare die VCSELs and photodiodes were thinned down to 20colonm and then packaged in flexible polyimide foils (40colonm thick) to allow fabricating this flexible and thin sensor. The use of spin-coatable polyimide resulted in low-stress packages for these optoelectronics.

The ring imaging Cherenkov (RICH) detector at LHCb is now read out by hybrid photon detectors. In view of its upgrade, a possible option is the adoption of the flat-panel photon multiplier tube (PMT). An important issue for good reconstruction of the Cherenkov rings is a negligible level of crosstalk. We have experimentally studied the crosstalk from the 16 × 16-pixels Hamamatsu H9500 PMT. Results have shown that, for the single-photon response, the statistics tied to the small number of electrons generated at the first dynode of the PMT chain (a few units) leads to a number of crosstalk signals that are a small fraction of the fired pixel. With the H9500, in a Cherenkov ring, only one or two pixels are expected to generate crosstalk. As a consequence, crosstalk cannot be considered a limit in the use of the H9500 for the upgrade of the RICH at LHCb. © 2010 IEEE.

Nonlinear optical (NLO) and electro-optical (EO) properties of π-conjugated systems have been the subject of intense interest during the past several decades. In this mini-review we focus on semiconducting materials based on alkyne π-conjugation, with particular emphasis on those examples from our laboratory of chromophores containing a silole core. Several closely related examples from the literature are also discussed.