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Enhancing light absorption by colloidal metal chalcogenide quantum dots <i>via</i> chalcogenol(ate) surface ligands
摘要： Chemical species at the surface (ligands) of colloidal inorganic semiconductor nanocrystals (QDs) markedly impact the optoelectronic properties of the resulting systems. Here, post-synthesis surface chemistry modification of colloidal metal chalcogenide QDs is demonstrated to induce both broadband absorption enhancement and band gap reduction. A comprehensive library of chalcogenol(ate) ligands is exploited to infer the role of surface chemistry on the QD optical absorption: the ligand chalcogenol(ate) binding group mainly determines the narrowing of the optical band gap, which is attributed to the np occupied orbital contribution to the valence band edge, and mediates the absorption enhancement, which is related to the π-conjugation of the ligand pendant moiety, with further contribution from electron donor substituents. These findings point to a description of colloidal QDs that may conceive ligands as part of the overall QD electronic structure, beyond models derived from analogies with core/shell heterostructures, which consider ligands as mere perturbation to the core properties. The enhanced light absorption achieved via surface chemistry modification may be exploited for QD-based applications in which an efficient light-harvesting initiates charge carrier separation or redox processes.
关键词： colloidal metal chalcogenide quantum dots,light absorption,optoelectronic properties,surface ligands,band gap reduction
更新于2025-10-22 19:40:53
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High-performance flexible transparent nanomesh electrodes
摘要： A cost-effective process for producing high-performance Ag-paste-based flexible transparent nanomesh electrodes was developed by optimizing their linewidth, pitch, and height. These nanomesh electrodes, with a linewidth of several hundred nanometers and a pitch of 10–200 μm on a PET substrate, achieved wide ranges of transmittance (83.1–98.8%) and sheet resistance (1.2–30.9 Ω/sq) and a figure of merit (992–1619) superior to those of indium tin oxide (ITO) and silver nanowire (AgNW) electrodes. Our evaluation of their flexibility (testing up to 50,000 cycles) and their electromagnetic interference shielding effectiveness verifies the applicability of these flexible transparent nanomesh electrodes to various flexible optoelectronic devices.
关键词： nanomesh,optoelectronic properties,flexible transparent conducting electrodes,Ag paste,phase-shifting edge lithography
更新于2025-09-23 15:23:52
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Quantum and Dielectric Confinement Effects in Lower-Dimensional Hybrid Perovskite Semiconductors
摘要： Hybrid halide perovskites are now superstar materials leading the field of low-cost thin film photovoltaics technologies. Following the surge for more efficient and stable 3D bulk alloys, multilayered halide perovskites and colloidal perovskite nanostructures appeared in 2016 as viable alternative solutions to this challenge, largely exceeding the original proof of concept made in 2009 and 2014, respectively. This triggered renewed interest in lower-dimensional hybrid halide perovskites and at the same time increasingly more numerous and differentiated applications. The present paper is a review of the past and present literature on both colloidal nanostructures and multilayered compounds, emphasizing that availability of accurate structural information is of dramatic importance to reach a fair understanding of quantum and dielectric confinement effects. Layered halide perovskites occupy a special place in the history of halide perovskites, with a large number of seminal papers in the 1980s and 1990s. In recent years, the rationalization of structure–properties relationship has greatly benefited from new theoretical approaches dedicated to their electronic structures and optoelectronic properties, as well as a growing number of contributions based on modern experimental techniques. This is a necessary step to provide in-depth tools to decipher their extensive chemical engineering possibilities which surpass the ones of their 3D bulk counterparts. Comparisons to classical semiconductor nanostructures and 2D van der Waals heterostructures are also stressed. Since 2015, colloidal nanostructures have undergone a quick development for applications based on light emission. Although intensively studied in the last two years by various spectroscopy techniques, the description of quantum and dielectric confinement effects on their optoelectronic properties is still in its infancy.
关键词： quantum confinement,multilayered perovskites,structural engineering,colloidal nanostructures,hybrid halide perovskites,optoelectronic properties,2D materials,dielectric confinement
更新于2025-09-23 15:23:52
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Tuning Carbon Dots’ Optoelectronic Properties with Polymers
摘要： Due to their unique properties of photoluminescence, biocompatibility, photostability, ease of preparing, and low cost, carbon dots have been studied extensively over the last decade. Soon after their discovery, it was realized that their main optical attributes may be protected, enhanced, and tuned upon proper surface passivation or functionalization. Therefore, up to date, numerous polymers have been used for these purposes, resulting to higher-quality carbon dots regarding their quantum yield or further emission-related aspects and compared to the primitive, bare ones. Hence, this review aims to clarify the polymers’ role and effect on carbon dots and their features focusing on the quality characteristics of their photoluminescence upon passivation or functionalization. Given in fact the numbers of relevant publications, emphasis is given on recent articles capturing the latest advances for polymers in carbon dots for expanding emission lifetimes, advancing quantum yields, tuning emission wavelengths, enhancing specific spectral range absorption, and tailoring optoelectronic properties in general.
关键词： photoluminescence,functionalization,carbon dots,polymers,optoelectronic properties,surface passivation
更新于2025-09-23 15:22:29
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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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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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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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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
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Processing and Study of Optical and Electrical Properties of (Mg, Al) Co-Doped ZnO Thin Films Prepared by RF Magnetron Sputtering for Photovoltaic Application
摘要： In this study, high transparent thin films were prepared by radio frequency (RF) magnetron sputtering from a conventional solid state target based on ZnO:MgO:Al2O3 (10:2 wt %) material. The films were deposited on glass and silicon substrates at the different working pressures of 0.21, 0.61, 0.83 and 1 Pa, 300 °C and 250 W of power. X-ray diffraction patterns (XRD), atomic force microscopy (AFM), UV-vis absorption and Hall effect measurements were used to evaluate the structural, optical, morphological and electrical properties of thin films as a function of the working pressure. The optical properties of the films, such as the refractive index, the extinction coefficient and the band gap energy were systematically studied. The optical band gap of thin films was estimated from the calculated absorption coefficient. That parameter, ranged from 3.921 to 3.655 eV, was hardly influenced by the working pressure. On the other hand, the lowest resistivity of 8.8 × 10?2 ? cm was achieved by the sample deposited at the lowest working pressure of 0.21 Pa. This film exhibited the best optoelectronic properties. All these data revealed that the prepared thin layers would offer a good capability to be used in photovoltaic applications.
关键词： working pressure,Al doped ZnO-MgO powder,RF magnetron sputtering,photovoltaic applications,thin films,solid-state method,optoelectronic properties
更新于2025-09-23 15:21:01