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- 2019
- microwave photonics
- optoelectronic oscillator
- frequency division
- Optoelectronic Information Science and Engineering
- Jinan University
- Charles Darwin University
- University of Ottawa
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Graphene Photonics || Optoelectronic Properties
摘要： In the preceding chapter, the surface optical conductivity eσeωT of graphene contributed by interband transitions was considered, which characterizes the optical response of graphene in the high-frequency region and has a real part given by (3.106) when the relaxation rate is taken to be zero by ignoring the finite relaxation times of the states involved in the transitions. We find by using this surface optical conductivity that monolayer graphene has an approximately constant absorbance of about 2.3 percent in the optical spectral region. However, in the low-frequency region, the surface optical conductivity eσeωT obtained in the preceding chapter is not valid. For example, if we set ω ? 0 for eσe0T to find the DC surface conductivity, we find that eσe0T is also zero, which is inconsistent with the DC surface conductivity obtained in Chapter 2. The discrepancy comes from the fact that eσeωT given in the preceding chapter only accounts for interband absorption of photons with electrons making transitions from a valence band to a conduction band, whereas the DC surface conductivity given in Chapter 2 is solely contributed by the intraband transitions of charge carriers within a valence band or within a conduction band.
关键词： Optoelectronic Properties,Surface Optical Conductivity,Intraband Transitions,Graphene,Interband Transitions
更新于2025-09-16 10:30:52
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Bulk recrystallization for efficient mixed-cation mixed-halide perovskite solar cells
摘要： Today, the use of mixed-cation lead mixed-halide perovskite with a slight excess of lead iodide (PbI2) demonstrates the highest device performances in the literature. However, the presence of excess PbI2 in the film poses long-term stability concerns. Here, we propose a facile bulk recrystallization process by applying formadinium chloride (FACl) on perovskite to remove excess PbI2 in the formed crystal. We are able to demonstrate bulk recrystallization, proved and observed by the Grazing incidence XRD to analyze the crystal structure as a function of depth profiling. The reconstructed crystal displays improved optoelectronic qualities with reduced interfacial recombination as well as enhanced device stability. When measured under AM 1.5G spectral conditions the optimized champion device reached a maximum power conversion efficiency (PCE) of 20.2%.
关键词： bulk recrystallization,optoelectronic qualities,FACl,perovskite solar cells,PbI2,device stability
更新于2025-09-16 10:30:52
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Highly stable CdTe quantum dots hosted in gypsum <i>via</i> a flocculation–precipitation method
摘要： Poor stability hinders the practical application of aqueous CdTe quantum dots (QDs) in optoelectronic devices. In this work, a flocculation–precipitation method is demonstrated to host aqueous CdTe QDs in gypsum to form CdTe–gypsum nanocomposites, which is simple, effective and environmental-friendly. Ascribed to gypsum acting as a tight and robust matrix protection agent, the photo-, thermal-, anti-acid and long-term stability of CdTe QDs were remarkably improved. Moreover, this approach solved the problem of incompatibility between aqueous QDs and epoxy resin, allowing for the application of aqueous QDs in white light emitting diodes (WLEDs), based on which a WLED with the red-emission nanocomposites used as a color-conversion layer was successfully fabricated. These results indicate the potential of this technique in stabilizing aqueous QDs as well as their practical application in optoelectronic devices.
关键词： optoelectronic devices,stability,flocculation–precipitation method,CdTe quantum dots,gypsum
更新于2025-09-16 10:30:52
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Nucleation-controlled growth of superior long oriented CsPbBr <sub/>3</sub> microrod single crystals for high detectivity photodetectors
摘要： There has been great interest in the use of cesium lead bromide (CsPbBr3), which is one of the most important members of the all-inorganic perovskite family, due to its superior optoelectronic performance and higher stability. Recently, it has been demonstrated that it is advantageous to use CsPbBr3 microrods and nanowires in photodetectors because of their higher crystallinity, low amount of defects, and easy control of carrier transport along a specific direction as compared to their counterparts of single crystals and thin films. However, there is a shortage of adequate investigations that describe how to control the growth of CsPbBr3 microrods and nanowires so that they retain the optoelectronic performance of single CsPbBr3 microrods. Therefore, we are reporting how to control the growth of orientated dispersive super-long CsPbBr3 microrod single crystals (CsPbBr3 MSCs) via a simple anti-solvent method. The crucial factor in controlling the growth of dispersive super-long CsPbBr3 MSCs is the regulation of the rapid nucleation rate and slowing of the growth rate via controlling the di?usion velocity of anti-solvent methanol. We also reveal the growth mechanism of CsPbBr3 MSCs as layer-by-layer growth that originates from the 2D nucleus. The CsPbBr3 MSCs are revealed grew in the direction of [010], with the (101) facet exposed. Moreover, photodetectors based on one CsPbBr3 MSC were fabricated, and the detectivity (D) and the on/o? ratio were as high as 3.67 (cid:2) 1012 Jones and 988, respectively, suggesting a very strong optoelectronic response as photodetectors. The mechanism that the Cs ions and Cs vacancies use to move to negative and positive electrodes along the channels constructed by [PbBr6]4(cid:3) in the [010] direction of the CsPbBr3 MSC (101) facet was revealed, after activation by the applied electrical field, which is beneficial to enhance the optoelectronic response but does not reduce the device stability.
关键词： anti-solvent method,optoelectronic performance,microrod single crystals,photodetectors,CsPbBr3
更新于2025-09-16 10:30:52
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Optoelectronic Measuring Systems for High-Voltage Installations Based on Photovoltaic Converters
摘要： We consider the main principles of construction of optoelectronic measuring systems in which the electric power supply of measuring modules is realized with the help of optical emission transmitted through a fiber light-guide. We present various versions of manufacturing of simple photovoltaic converters with a conversion efficiency of up to 50% based on the photodiode assemblies and AlGaAs light-emitting diodes. The factors limiting the power supplied by the optical emission are analyzed. The possibilities of realization of measuring modules based on self-excited generators with resistive and capacitive transducers based on multichannel analog-to-digital converters are presented. The methods aimed at decreasing the energy consumption of the measuring modules are analyzed.
关键词： fiber optics,optoelectronic measuring systems,sensors,optical powering
更新于2025-09-16 10:30:52
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Concise synthesis of 3-alkylthieno[3,2- <i>b</i> ]thiophenes; building blocks for organic electronic and optoelectronic materials
摘要： Four step synthesis of 3-alkylthieno[3,2-b]thiophenes in the literature was reduced to two steps in good yields, through the preparation of the mono ketone, i.e. 1-(thiophene-3-ylthio)alkan-2-one, from 3-bromothiophene and ring formation reaction. This convenient method provides an easy access with good yields to the preparation of 3-alkylthieno[3,2-b]thiophenes, which are important materials for organic electronic and optoelectronic applications. SEM, AFM and contact angle (CA) analyses of their electropolymers on indium tin oxide (ITO) indicated that as the alkyl chains became longer, the polymers provide a more hydrophobic layer with CA up to 107°.
关键词： optoelectronic materials,hydrophobic layer,synthesis,organic electronic,3-alkylthieno[3,2-b]thiophenes
更新于2025-09-16 10:30:52
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Towards highly efficient thin-film solar cells with a graded-bandgap CZTSSe layer
摘要： A coupled optoelectronic model was implemented along with the differential evolution algorithm to assess the efficacy of grading the bandgap of the Cu2ZnSn(SξSe1?ξ)4 (CZTSSe) layer for enhancing the power conversion efficiency of thin-film CZTSSe solar cells. Both linearly and sinusoidally graded bandgaps were examined, with the molybdenum backreflector in the solar cell being either planar or periodically corrugated. Whereas an optimally graded bandgap can dramatically enhance the efficiency, the effect of periodically corrugating the backreflector is modest at best. An efficiency of 21.74% is predicted with sinusoidal grading of a 870-nm-thick CZTSSe layer, in comparison to 12.6% efficiency achieved experimentally with a 2200-nm-thick homogeneous CZTSSe layer. High electron-hole-pair generation rates in the narrow-bandgap regions and a high open-circuit voltage due to a wider bandgap close to the front and rear faces of the CZTSSe layer are responsible for the high enhancement of efficiency.
关键词： optoelectronic optimization,Bandgap grading,thin-film solar cell,earth-abundant materials,CZTSSe solar cell
更新于2025-09-16 10:30:52
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In Situ Light-Initiated Ligands Crosslinking Enables Efficient All-Solution-Processed Perovskite Light-Emitting Diodes
摘要： Solution process has been considered to be an effective method to fabricate emitting layer (EML) in light-emitting diodes (LEDs). However, the fabrication of charge transport layer (CTL) above the perovskite EML by solution processing is challenging. Herein, we incorporated polymerizable molecules, conjugated linoleic acid (CLA), as surface ligands to passivate perovskite QDs. The polymerized CLA can create a crosslinked QD film, which allows the solution deposition of subsequent CTLs. The theoretical calculations reveal that the binding energy of polymerized CLA with QDs increased, and the strong ligands binding state can better passivate the surface and improve the stability of QDs. As a result, all-solution-processed multilayer perovskite LEDs were fabricated with performance of a max luminance of 2470 cd/m2 for CsPbBr3-based devices, and a peak EQE of 2.67% for CsPbI3-based devices. These results demonstrate that the in situ light-initiated ligands crosslinking can be an effective strategy in all-solution-processed optoelectronic devices.
关键词： optoelectronic devices,light-emitting diodes,solution processing,perovskite quantum dots,ligands crosslinking
更新于2025-09-16 10:30:52
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Dibenzo[ <i>hi</i> , <i>st</i> ]ovalene as Highly Luminescent Nanographene: Efficient Synthesis via Photochemical Cyclodehydroiodination, Optoelectronic Properties, and Single-Molecule Spectroscopy
摘要： Dibenzo[hi,st]ovalene (DBOV), as a new nanographene, has demonstrated promising optical properties, such as red emission with a high fluorescence quantum yield of 79% and stimulated emission, as well as high thermal stability and photostability, which indicated its promise as a light-emitting and optical gain material. However, the previous synthetic routes required at least 12 steps. This obstructed access to different derivatives, e.g., to obtain crystals suitable for X-ray diffraction analysis and to tune the optoelectronic properties. Here, we report an efficient synthetic pathway to DBOV based on a sequential iodination-benzannulation of bi(naphthylphenyl)diyne, followed by photochemical cyclodehydroiodination (PCDHI). This protocol included a fused bischrysene as a key intermediate and furnished scalable amounts of meso-substituted DBOV derivatives with different substituents. DBOV with 2,6-dimethylphenyl groups could be used for single-crystal X-ray analysis, revealing the precise structure of the DBOV core. The optoelectronic properties of the DBOV derivatives were investigated by UV?vis absorption and fluorescence spectroscopy, cyclic voltammetry, and density functional theory calculations. Single-molecule spectroscopy at room and low temperatures provided novel insights into the photophysics of DBOV embedded in a polymer film. As a result of weak coupling of the optical transitions to the matrix, single-molecule emission spectra at 4.5 K showed narrow vibronic lines. The fluorescence autocorrelation function covering 9 orders of magnitude in time displayed high contrast photon antibunching and bunching, from which the fluorescence decay rate and the triplet population and depopulation rates could be retrieved. Remarkably, the intersystem crossing rate into the triplet state decreased by more than an order of magnitude at low temperature, demonstrating that temperature can be a crucial parameter to boost single photon emission of an aromatic hydrocarbon.
关键词： fluorescence quantum yield,nanographene,single-molecule spectroscopy,optoelectronic properties,photochemical cyclodehydroiodination
更新于2025-09-16 10:30:52
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Evidence for Ferroelectricity of All-Inorganic Perovskite CsPbBr3 Quantum Dots
摘要： The ferroelectric-optical combination of properties in halide perovskites has attracted tremendous interests because of its potential for optoelectronic and energy applications. However, very few reports focus on the ferroelectricity of all-inorganic halide perovskites quantum dots. Herein, we report a excellent ferroelectricity in CsPbBr3 quantum dots (QDs) with a saturation polarization of 0.25 μC/cm2. Differential scanning calorimeter (DSC), X-ray diffraction (XRD), transmission electronic microscopy (TEM) revealed that the mechanism of ferroelectric-paraelectric switching of CsPbBr3 QDs can be attributed to the phase transition from cubic phase (????3??) to orthorhombic phase (Pna21). In the orthorhombic CsPbBr3, the distortion of octahedral [PbBr6]4- structural units and the off-center Cs+ generated the slightly separated centres of positive charge and negative charge, resulting in the ferroelectric properties. The variable temperature emission spectrum from 328 K to 78 K exhibits green luminescence and the gradually red shift due to the phase transition. This finding opens up a avenue to explore the ferroelectric-optical properties of inorganolead halide perovskites for high-performance multifunctional materials.
关键词： CsPbBr3 quantum dots,all-inorganic perovskite,phase transition,optoelectronic applications,ferroelectricity
更新于2025-09-16 10:30:52