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Theoretical investigation on the third order nonlinear optical susceptibility in CdS/ZnS/CdS/ZnS core/shell/well/shell quantum dots for optoelectronic applications
摘要： In this paper, a detailed study on the third order nonlinear optical susceptibility for quadratic electro-optic effects for CdS/ZnS/CdS/ZnS core/shell/well/shell spherical quantum dots is realized. Electron energies and corresponding functions are investigated under the frame work of the effective-mass approximation. Then, the third order nonlinear susceptibility is determined using the density matrix method. The dot size effect on this susceptibility is also examined. Numerical calculations confirm that both position and intensity of the peaks can be controlled by varying shell thickness. In addition, by increasing the width of inner or outer shell, the peaks of susceptibility is redshifted and the intensities are increased. Moreover, the 'inverted' structure, ZnS/CdS/ZnS/CdS has shown better nonlinear optical properties.
关键词： third order nonlinear susceptibility,II-VI Semiconductors,Quantum dot quantum well
更新于2025-09-23 15:19:57
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Liquid Phase Exfoliated Indium Selenide Based Highly Sensitive Photodetectors
摘要： Layered semiconductors of the IIIA–VIA group have attracted considerable attention in (opto)electronic applications thanks to their atomically thin structures and their thickness-dependent optical and electronic properties, which promise ultrafast response and high sensitivity. In particular, 2D indium selenide (InSe) has emerged as a promising candidate for the realization of thin-film field effect transistors and phototransistors due to its high intrinsic mobility (>102 cm2 V?1 s?1) and the direct optical transitions in an energy range suitable for visible and near-infrared light detection. A key requirement for the exploitation of large-scale (opto)electronic applications relies on the development of low-cost and industrially relevant 2D material production processes, such as liquid phase exfoliation, combined with the availability of high-throughput device fabrication methods. Here, a β polymorph of indium selenide (β-InSe) is exfoliated in isopropanol and spray-coated InSe-based photodetectors are demonstrated, exhibiting high responsivity to visible light (maximum value of 274 A W?1 under blue excitation 455 nm) and fast response time (15 ms). The devices show a gate-dependent conduction with an n-channel transistor behavior. Overall, this study establishes that liquid phase exfoliated β-InSe is a valid candidate for printed high-performance photodetectors, which is critical for the development of industrial-scale 2D material-based optoelectronic devices.
关键词： photodetectors,2D semiconductors,indium selenide,field effect transistors,liquid phase exfoliation,spray coating,solution processed
更新于2025-09-23 15:19:57
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Significant Performance Improvement of Oxide Thin-Film Transistors by a Self-Assembled Monolayer Treatment
摘要： Despite being a standard process in fabrication of organic thin-film transistors (TFTs) to reduce interface trap density and decrease surface energy, self-assembled monolayer (SAM) treatment of gate dielectrics is rarely used in oxide-semiconductor-based TFTs due to possible damage to the SAM during semiconductor deposition. Here, by studying the dependence of plasma damage to SAM on the deposition conditions of InGaZnO (IGZO) semiconductor thin films, the feasibility of enhancing the performance of oxide TFTs using octadecyl-trichlorosilane (OTS)-treated, ultra-thin AlxOy gate dielectrics is explored. It is discovered that under optimized conditions, the TFTs can be significantly improved, showing a reduction of interface trap density by 50% and an increase of carrier mobility and current on/off ratio by a factor of 2.3 and 76, respectively. The effects on bias stress stability also show substantial improvement after the SAM interface treatment. Finally, such an optimized condition is found to also work for IGZO TFTs gated with OTS-treated HfOx, showing an increase of mobility from 7.8 to 16 cm2 V?1 s?1 compared with the untreated devices. As a result, this simple and yet effective interface treatment method and the resulting devices may have potential applications in future low-cost, low-power electronics.
关键词： interface treatment,octadecyltrichlorosilane,self-assembled monolayers,thin-film transistors,oxide semiconductors
更新于2025-09-23 15:19:57
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Magnetic bipolar transistor based on ZnO/NiO/Si heterostructure using pulsed laser deposition
摘要： Oxide semiconductors are promising candidates for next generation electronics. In this work, magnetic bipolar transistor was fabricated by growing thin films of p-NiO and n-ZnO on n-type silicon wafer by pulsed laser deposition technique with an in-situ annealing at 670○ C in the presence of oxygen. The structural characterization of these films was done by X-ray diffraction and Raman spectroscopy and magnetic properties were studied by vibrating sample magnetometer (VSM). I-V characteristic of fabricated transistor was tested in common emitter configuration with DC biasing. Junction parameters such as ideality factor, series resistance, and transistor parameters like q-point were determined by using conventional transistor output characteristics. The diode and transistor showed an increase in current with the externally applied magnetic field due to the presence of Nickel or Oxygen vacancies in NiO attributing to spin polarized bipolar transport. Therefore the current amplification in these devices can be controlled by spin; making it attractive for spintronic applications.
关键词： oxide semiconductors,pulsed laser deposition,spintronic applications,magnetic bipolar transistor
更新于2025-09-23 15:19:57
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Chargea??Transfera??Controlled Growth of Organic Semiconductor Crystals on Graphene
摘要： Controlling the growth behavior of organic semiconductors (OSCs) is essential because it determines their optoelectronic properties. In order to accomplish this, graphene templates with electronic-state tunability are used to affect the growth of OSCs by controlling the van der Waals interaction between OSC ad-molecules and graphene. However, in many graphene-molecule systems, the charge transfer between an ad-molecule and a graphene template causes another important interaction. This charge-transfer-induced interaction is never considered in the growth scheme of OSCs. Here, the effects of charge transfer on the formation of graphene–OSC heterostructures are investigated, using fullerene (C60) as a model compound. By in situ electrical doping of a graphene template to suppress the charge transfer between C60 ad-molecules and graphene, the layer-by-layer growth of a C60 film on graphene can be achieved. Under this condition, the graphene–C60 interface is free of Fermi-level pinning; thus, barristors fabricated on the graphene–C60 interface show a nearly ideal Schottky–Mott limit with efficient modulation of the charge-injection barrier. Moreover, the optimized C60 film exhibits a high field-effect electron mobility of 2.5 cm2 V?1 s?1. These results provide an efficient route to engineering highly efficient optoelectronic graphene–OSC hybrid material applications.
关键词： growth template,organic semiconductors,organic electronics,graphene,charge transfer
更新于2025-09-23 15:19:57
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Largea??Scale Ultrathin 2D Widea??Bandgap BiOBr Nanoflakes for Gatea??Controlled Deepa??Ultraviolet Phototransistors
摘要： Ternary two-dimensional (2D) semiconductors with controllable wide bandgap, high ultraviolet (UV) absorption coefficient, and critical tuning freedom degree of stoichiometry variation have a great application prospect for UV detection. However, as-reported ternary 2D semiconductors often possess a bandgap below 3.0 eV, which must be further enlarged to achieve comprehensively improved UV, especially deep-UV (DUV), detection capacity. Herein, sub-one-unit-cell 2D monolayer BiOBr nanoflakes (≈0.57 nm) with a large size of 70 μm are synthesized for high-performance DUV detection due to the large bandgap of 3.69 eV. Phototransistors based on the 2D ultrathin BiOBr nanoflakes deliver remarkable DUV detection performance including ultrahigh photoresponsivity (Rλ, 12739.13 A W?1), ultrahigh external quantum efficiency (EQE, 6.46 × 106%), and excellent detectivity (D*, 8.37 × 1012 Jones) at 245 nm with a gate voltage (Vg) of 35 V attributed to the photogating effects. The ultrafast response (τrise = 102 μs) can be achieved by utilizing photoconduction effects at Vg of ?40 V. The combination of photocurrent generation mechanisms for BiOBr-based phototransistors controlled by Vg can pave a way for designing novel 2D optoelectronic materials to achieve optimal device performance.
关键词： monolayer BiOBr,deep UV phototransistors,wide-bandgap semiconductors,high gain
更新于2025-09-23 15:19:57
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Efficiency Limits of Underwater Solar Cells
摘要： Operation of underwater vehicles and autonomous systems is currently limited by the lack of long-lasting power sources. These systems could potentially be powered using underwater solar cells, but the material requirements to achieve their full potential are not well understood. Using detailed-balance calculations, we show that underwater solar cells can exhibit efficiencies from ~55% in shallow waters to more than 65% in deep waters, while maintaining a power density >5 mW cm?2. We show that the optimum band gap of the solar cell shifts by ~0.6 eV between shallow and deep waters and plateaus at ~2.1 eV at intermediate depths, independent of geographical location. This wide range in optimum band-gap energies opens the potential for a library of wide-band-gap semiconductors to be used for high-efficiency underwater solar cells. Our results provide a roadmap for proper choice of underwater solar cell materials, given the conditions at points of use.
关键词： wide-band-gap semiconductors,detailed-balance calculations,efficiency limits,power density,underwater solar cells
更新于2025-09-23 15:19:57
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Non-covalent Interaction Controlled 2D Organic Semiconductor Films: Molecular Self-Assembly, Electronic and Optical Properties, and Electronic Devices
摘要： The establishment of electronic and opto-electronic products relying on organic semiconductors (OSCs) has been intensely explored over the past few decades due to their great competitiveness in large area, low cost, flexible, wearable and implantable devices. Many of these products already entered our daily lives, such as organic light-emitting diodes-based displays, portable organic solar cells and organic field-effect transistors. The device performance of OSC devices are determined by the supramolecular organization (orientation, morphology) as well as the supramolecular organization dependent energy level alignment at various interfaces (organic/electrode, organic/dielectric, organic/organic). This review focuses on the impact of non-covalent interaction on the molecular self-assembly of organic thin films, their electronic and optical properties, as well as the device performance. Beginning with the growth of multiple OSCs on substrates with different interfacial interaction strengths (metals, insulators, semiconductors), the critical roles of molecule-substrate and intermolecular interactions in determining the thin film organization have been demonstrated. Several non-covalent interactions that contribute to the energy levels of organic materials in solid phase are summarized, mainly including the induction contributions, electrostatic interactions, band dispersions and interface dipoles. The excitonic coupling in specific aggregations of organic molecules and the corresponded effect on their optical properties are also discussed. Finally, the influences of weak intermolecular interactions on the device performance are presented.
关键词： molecular self-assembly,optical properties,non-covalent interaction,electronic properties,electronic devices,organic semiconductors
更新于2025-09-23 15:19:57
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Monolithic Contact Engineering to Boost Optoelectronic Performances of 2D Semiconductor Photovoltaic Heterojunctions
摘要： In optoelectronic devices based on two-dimensional (2D) semiconductor heterojunctions, the efficient charge transport of photogenerated carriers across the interface is a critical factor to determine the device performances. Here, we report an unexplored approach to boost the optoelectronic device performances of the WSe2-MoS2 p-n heterojunctions via the monolithic-oxidation-induced doping and resultant modulation of the interface band alignment. In the proposed device, the atomically thin WOx layer, which is directly formed by layer-by-layer oxidation of WSe2, is used as a charge transport layer for promoting hole extraction. The use of the ultrathin oxide layer significantly enhanced the photoresponsivity of the WSe2-MoS2 p-n junction devices, and the power conversion efficiency increased from 0.7 to 5.0%, maintaining the response time. The enhanced characteristics can be understood by the formation of the low Schottky barrier and favorable interface band alignment, as confirmed by band alignment analyses and first-principle calculations. Our work suggests a new route to achieve interface contact engineering in the heterostructures toward realizing high-performance 2D optoelectronics.
关键词： Contact engineering,Transition metal dichalcogenides,Heterostructures,Photovoltaics,2D semiconductors,Optoelectronics
更新于2025-09-23 15:19:57
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Photodetectors based on solution-processable semiconductors: Recent advances and perspectives
摘要： The detection of light, one of the most important technologies, has widespread applications in industry and our daily life, e.g., environmental monitoring, communications, surveillance, image sensors, and advanced diagnosis. Along with the remarkable progress in the field of organics, those based on quantum dots, and recently emerged perovskite optoelectronics, photodetectors based on these solution-processable semiconductors have shown unprecedented success. In this review, we present the basic operation mechanism and the characterization of the performance metrics based on these novel materials systems. Then, we focus on the current research status and recent advances with the following five aspects: (i) spectral tunability, (ii) cavity enhanced photodetectors, (iii) photomultiplication type photodetectors, (iv) sensitized phototransistors, and (v) ionizing radiation detection. At the end, we discuss the key challenges facing these novel photodetectors toward manufacture and viable applications. We also point out the opportunities, which are promising to explore and may require more research activities.
关键词： sensitized phototransistors,photodetectors,cavity enhanced photodetectors,solution-processable semiconductors,photomultiplication type photodetectors,spectral tunability,ionizing radiation detection
更新于2025-09-23 15:19:57