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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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Improving the performance of Cu2ZnSnS4 thin film solar cell by engineering the ITO film thickness
摘要： In this work, the effects of tin doped indium oxide (ITO) thin films with different thicknesses (50 nm–476 nm) on the optoelectronic performance were investigated. Meanwhile, the sputtered ITO layers were annealed at 180°C for 60min under air atmosphere. The result indicated that the electro-optical properties of ITO films with the thickness (383 nm) were optimum, and the corresponding resistivity and average reflectance in the spectrum range (350–860 nm) were 4.73 × 10?4 Ω cm and lower than 20%, respectively. Finally, impacts of ITO layers with various thicknesses on the performance of CZTS solar cells were also studied. The open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE) of CZTS solar cells had been increased significantly from 576 mV to 636 mV, from 15.8 mA/cm2 to 20.2 mA/cm2, from 31.2% to 43.4% and from 3.04% to 5.56%, respectively, and eventually the highest PCE of CZTS solar cell based on 383 nm ITO window layer thickness was 5.56%.
关键词： Power conversion efficiency,ITO films,Reflectance,Optoelectronic performance
更新于2025-09-23 15:21:01
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Inverted Hybrid Light-Emitting Diodes Using Carbon Dots as Selective Contacts: The Effect of Surface Ligands
摘要： We describe the use of carbon dots (C-Dots) as selective contacts for electronic holes in inverted hybrid light-emitting diodes. Moreover, we have studied the effect of the C-Dots’ amine-derivative surface ligands and their impact on the device performance. The different surface ligands affect not only the optical properties of the C-Dots but also the device turn-on voltage and the luminance parameters despite not forming part of the emissive layer. For instance, the C-Dots capped with the aromatic ring p-phenylenediamine show unfavorable effects, whereas the effect of nonaromatic capping ligands depends upon the length of their molecular backbone.
关键词： capping ligands,amine-based ligands,light-emitting diodes,carbon dots,optoelectronic properties
更新于2025-09-23 15:21:01
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Molecular Packing: Another Key Point for the Performance of Organic and Polymeric Optoelectronic Materials
摘要： Optoelectronic material properties are governed by the whole collective of organic moieties, and these aggregate states present the characteristic performance of extended assemblies with different molecular packing, not only of single molecules themselves. Thus, controlling molecular packing is an essential issue for obtaining the optimized optical and electronic properties. It is also a great challenge because of the unclear structures and complicated intermolecular interactions, including dispersion forces, electrostatic interactions and hydrogen bonding. Moreover, upon the introduction of some external force as the stimulus source, dynamic optical properties can be achieved with the transformation of the photoinduced room temperature molecular packing in some cases, phosphorescence (RTP) effect, mechanochromic luminescence, treatment-dependent mechanoluminescence effect, and the optimized nonlinear optical (NLO) property achieved after electric poling. Therefore, it is essential to understand the relation between characteristics of molecular packing and the resultant optoelectronic performance at the molecular level, which becomes increasingly demanding for the further development of functional materials for their applications in organic light-emitting diodes (OLEDs), chemo- and biosensors, organic solar cells, data storage, and anticounterfeiting devices.
关键词： aggregate states,dynamic optical properties,optoelectronic materials,molecular packing,intermolecular interactions
更新于2025-09-23 15:21:01
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[IEEE 2019 International Workshop on Fiber Optics in Access Networks (FOAN) - Sarajevo, Bosnia and Herzegovina (2019.9.2-2019.9.4)] 2019 International Workshop on Fiber Optics in Access Networks (FOAN) - An Affordable Laboratory Photodiode up to 11.5 GHz for Microwave Photonics Experiments
摘要： Low-cost optoelectronic devices are the main limiting factor when it comes to scaling the current access networks based on microwave photonics to the capabilities of smart cities. The use of affordable photodiodes could decrease the use of microwave photonics, since it is part of each system. In this paper we evaluate the frequency response of a coaxial packaged photodiode. The design of an electric circuit is presented. The results from the vector network analyzer show that the coaxial packaged photodiode makes photodetectors applicable up to 11.5 GHz. In addition, an experimental verification of the photodiode in an optoelectronic oscillator is performed.
关键词： photodetector,optoelectronic oscillator,photodiode,microwave photonics
更新于2025-09-23 15:21:01
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Microstructure characteristics of non-monodisperse quantum dots: On the potential of transmission electron microscopy combined with X-ray diffraction
摘要： Although the concept of quantum confinement was introduced more than thirty years ago, a wide application of the quantum dots is still limited by the fact that monodisperse quantum dots with controlled optoelectronic properties are typically synthesized on a relatively small scale. Larger scale synthesis techniques are usually not able to produce monodisperse nanoparticles yet. In this contribution, we illustrate the capability of the combination of transmission electron microscopy and X-ray diffraction to reveal detailed and scale-bridging information about the complex microstructure of non-monodisperse quantum dots, which is the first step towards a further upscalling of the techniques for production of quantum dots with controlled properties. As a model system, CdSe quantum dots synthesized using an automated robotic hot-injection method at different temperatures were chosen. The combined microstructure analytics revealed the size and shape of the CdSe nanocrystals and the kind, density and arrangement of planar defects. The role of the planar defects in the particle coarsening by oriented attachment and the effect of the planar fault arrangement on the phase constitution, on the crystallographic coherence of the counterparts and on the optoelectronic properties are discussed.
关键词： microstructure,optoelectronic properties,planar defects,transmission electron microscopy,X-ray diffraction,quantum dots,oriented attachment,CdSe
更新于2025-09-23 15:21:01
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[NH3(CH2)6NH3]PbI4 as Dion-Jacobson Phase Bifunctional Capping Layer for 2D/3D Perovskite Solar Cells with High Efficiency and Excellent UV Stability
摘要： Currently, three-dimensional (3D) organic–inorganic hybrid metallic halide perovskites are emerging as optoelectronic materials, but they demonstrate poor stability against heat and moisture and are vulnerable to oxidation and photodegradation upon exposure to ultraviolet (UV) light. Herein, for the first time, 1,6-diaminohexane ammonium (HDAD+) is demonstrated to be a unique cation spacer to prepare a two-dimensional Dion-Jacobson phase (DJP) perovskite that is ultimately used to construct a 2D/3D stacking structure. Compared to 3D perovskites and Ruddlesden-Popper phase (RPP)-2D perovskites, the DJP-2D perovskite demonstrates superior UV stability and can efficiently protect the 3D layer underneath from being damaged by the UV light. Moreover, the DJP-2D perovskite can also act as an interfacial layer to passivate the defects located on top of the 3D perovskite, resulting in a notably increased photoluminescence lifetime and suppression of interfacial charge recombination. As a result, the power conversion efficiency (PCE) is enhanced from 19.22% (3D) to 20.31% (2D/3D) and is accompanied by improved moisture and thermal stabilities.
关键词： Dion-Jacobson phase,2D/3D stacking structure,UV stability,optoelectronic materials,perovskite solar cells
更新于2025-09-23 15:21:01
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Fabrication and optoelectronic properties of Ga2O3/Eu epitaxial films on nanoporous GaN distributed Bragg reflectors
摘要： Nanoporous GaN distributed Bragg re?ectors (DBRs) with a high re?ectivity (* 92%), which was fabricated via a doping selective electrochemical etching process, were used to deposit Eu-doped b-Ga2O3 ?lms by using pulsed layer deposition. Structural and chemical composition analyses indicated that the 900 (cid:3)C-annealed ?lm in air has the best crystalline quality and highest photo-luminescence (PL) ef?ciency. The epitaxial relationship between the b-Ga2O3: Eu ?lm and DBR mirror was Ga2O3 (201)kGaN (0001) with Ga2O3 [010]kGaN [1210]. Compared to the Eu:Ga2O3 ?lm on reference template, the 900 (cid:3)C-an-nealed ?lm on the DBR mirror presented a * 20-fold enhancement in the PL emission. The performance enhancement was attributed to light-coupling enhancement of the buried DBR mirror. Because of the good electrical properties of the annealed ?lms, the fabricated DBR substrates pave the way for devel-oping a range of rare-earth-doped Ga2O3 optoelectronic devices.
关键词： Ga2O3/Eu,optoelectronic properties,pulsed layer deposition,distributed Bragg re?ectors,nanoporous GaN
更新于2025-09-23 15:21:01
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Ultrafast dynamics in van der Waals heterostructures
摘要： Van der Waals heterostructures are synthetic quantum materials composed of stacks of atomically thin two-dimensional (2D) layers. Because the electrons in the atomically thin 2D layers are exposed to layer-to-layer coupling, the properties of van der Waals heterostructures are defined not only by the constituent monolayers, but also by the interactions between the layers. Many fascinating electrical, optical and magnetic properties have recently been reported in different types of van der Waals heterostructures. In this Review, we focus on unique excited-state dynamics in transition metal dichalcogenide (TMDC) heterostructures. TMDC monolayers are the most widely studied 2D semiconductors, featuring prominent exciton states and accessibility to the valley degree of freedom. Many TMDC heterostructures are characterized by a staggered band alignment. This band alignment has profound effects on the evolution of the excited states in heterostructures, including ultrafast charge transfer between the layers, the formation of interlayer excitons, and the existence of long-lived spin and valley polarization in resident carriers. Here we review recent experimental and theoretical efforts to elucidate electron dynamics in TMDC heterostructures, extending from timescales of femtoseconds to microseconds, and comment on the relevance of these effects for potential applications in optoelectronic, valleytronic and spintronic devices.
关键词： spin and valley polarization,charge transfer,valleytronic,transition metal dichalcogenide,Van der Waals heterostructures,excited-state dynamics,spintronic devices,interlayer excitons,optoelectronic
更新于2025-09-23 15:21:01
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Theoretical study of Da??Aa?2a????a??A/Da????a??Aa?2a????a??A triphenylamine and quinoline derivatives as sensitizers for dye-sensitized solar cells
摘要： We have designed four dyes based on D–A0–p–A/D–p–A0–p–A triphenylamine and quinoline derivatives for dye-sensitized solar cells (DSSCs) and studied their optoelectronic properties as well as the e?ects of the introduction of alkoxy groups and thiophene group on these properties. The geometries, single point energy, charge population, electrostatic potential (ESP) distribution, dipole moments, frontier molecular orbitals (FMOs) and HOMO–LUMO energy gaps of the dyes were discussed to study the electronic properties of dyes based on density functional theory (DFT). And the absorption spectra, light harvesting e?ciency (LHE), hole–electron distribution, charge transfer amount from HOMO to LUMO (QCT), D index, HCT index, Sm index and exciton binding energy (Ecoul) were discussed to investigate the optical and charge-transfer properties of dyes by time-dependent density functional theory (TD-DFT). The calculated results show that all the dyes follow the energy level matching principle and have broadened absorption bands at visible region. Besides, the introduction of alkoxy groups into triarylamine donors and thiophene groups into conjugated bridges can obviously improve the stability and optoelectronic properties of dyes. It is shown that the dye D4, which has had alkoxy groups as well as thiophene groups introduced and possesses a D–p–A0–p–A con?guration, has the optimal optoelectronic properties and can be used as an ideal dye sensitizer.
关键词： alkoxy groups,thiophene group,density functional theory,dye-sensitized solar cells,D–A0–p–A/D–p–A0–p–A,triphenylamine,quinoline derivatives,time-dependent density functional theory,optoelectronic properties
更新于2025-09-23 15:21:01
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Effect of the alkyl chain length on the optoelectronic properties of organic dyes: theoretical approach
摘要： In recent years, investigating organic compounds for Dye Sensitized Solar Cells (DSSCs) applications has received particular attention for its interesting optoelectronics properties. In this article, we have conducted a theoretical study on a series of D–π–A molecules, which have carbazole as a donor (D) and cyanoacrylic acid as acceptor (A) linked by a conjugated bridge. Theoretical calculations were conducted using Density Functional Theory (DFT) and Time-Dependent-DFT to evaluate the substitution effect of linear chains and to elucidate the effects of alkyl chain length (R: H, CH3 to C6H13). We have studied the geometrical structures, the electronic and optical properties, the conduction band shift, as well as the charge transfer parameters: IP, EA, PEE, HEP, λ, LHE, Voc, ΔGinject and ΔGreg of the studied dyes. According to the results obtained, the substitution of hydrogen H (Dye 1) by the methyl group CH3 (Dye 2) has, on the one hand, a significant effect on the values of the energies HOMO and LUMO, and on the other hand, the absorption peak is redshifted and the contribution of the electronic transition (H → L) has been improved (664.17 nm and 70%, respectively). However, the substitution of CH3 (Dye 2) by the other alkyl groups CnH2n+1 (n = 2 to 6) (Dye 3 to Dye 7) has low effects. The best results are obtained by substitution with methyl CH3, and the increase in chain length, which will require additional computing time, has a low effect on the properties of the dyes studied.
关键词： DFT,Optoelectronic properties,Alkyl chain length,Dyes
更新于2025-09-23 15:21:01