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Efficiency enhancement in PbS/CdS quantum dot-sensitized solar cells by plasmonic Ag nanoparticles
摘要： Semiconductor quantum dots (Q-dots) are attractive nanomaterials to be used in numerous research areas and device fabrication such as sensors, transistors, and solar cells due to their unique optoelectronic properties. Quantum dot-sensitized solar cells (QDSSCs) have drawn considerable attention due to their cost-effectiveness and ability of multiple exciton generation and tunable energy gap of the quantum dots. In this study, plasmonic Ag colloidal nanoparticle-incorporated plasmonic TiO2 double-layer (nanofiber/nanoparticle) electrodes have been fabricated. These TiO2 electrodes were sensitized with PbS/CdS core-shell quantum dots by successive ionic layer adsorption and reaction (SILAR) technique, and QDSSCs were fabricated with polysulfide electrolyte. Cu2S was formed on brass plate and used as the counter electrode of the QDSSC. A higher power conversion efficiency of 4.09% has been obtained due to the plasmonic effect under the simulated light of 100 mW cm?2 with AM 1.5 spectral filter. The overall efficiency and short-circuit current density of the plasmonic QDSSC are enhanced by 15% and 23%, respectively, with respect to the QDSSC without Ag nanoparticles. The enhanced performance of the plasmonic QDSSC is evidently due to the enhanced optical absorption by localized surface plasmon resonance effect by the Ag nanoparticles in the TiO2 photoanode and the resulting increase in the short-circuit photocurrent.
关键词： Energy gap,Ag nanoparticles,Surface plasmon resonance,Quantum dots,Multiple exciton generation
更新于2025-09-16 10:30:52
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Ternary organic solar cells with NC70BA as a third component material exhibit high open-circuit voltage and small energy losses
摘要： The ternary organic solar cells (OSCs) were fabricated with PBDB-T as donor and a blend of IEICO-4F and NC70BA as the acceptor and the power conversion efficiency (PCE) reaches 10.92%. Due to good compatibility and cascade LUMO level among PBDB-T, a large amount of IEICO-4F and a small amount of NC70BA (the ratio of IEICO-4F:NC70BA is 85:15), which beneficial for adjusting lowest unoccupied molecular orbital (LUMO) levels of blend acceptor and wide energy offset between the donor and acceptor materials, leading to the enhancement of the open-circuit voltage (VOC). The optimized ternary PBDB-T:IEICO-4F:NC70BA films is more efficient exciton dissociation and suppress charge carrier recombination than that of binary PBDB-T:IEICO-4F and PBDB-T:NC70BA films, leading to small energy losses. In addition, this approach maintains PCE without sacrificing short-circuit current density (JSC) and fill factor (FF), even if the weak long and near-infrared wavelength photon harvesting. A more than 10% PCE improvement is achieve by employing a ternary strategy in comparison to PBDB-T:IEICO-4F-based binary OSCs with a PCE of 9.87%. Simultaneously, the optimized ternary PBDB-T:IEICO-4F:NC70BA OSCs exhibit the excellent thermal stability and 78.8% initial PCE under thermal annealing treatment at 80°C for 20 h.
关键词： Energy loss,Charge carrier recombination,Exciton dissociation
更新于2025-09-16 10:30:52
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The effect of introducing antibiotics into organic light-emitting diodes
摘要： The quest to improve the performance of organic light-emitting diodes (OLEDs) has led to the exploration of new materials with properties like interfacial dipole, excitons generation, and bandgap alignment. Here, we exploit these strategies by investigating the interaction of the antibiotic ampicillin with a widely used optoelectronic material, to fabricate state-of-the-art OLEDs. The charge distribution on the ampicillin molecule facilitates the generation of an interfacial dipole with a large magnitude. The optimum fusion of the two materials provides an enhanced bandgap alignment, charge balance and J/H-aggregated excitons. Values of current efficiency (120 cdA?1), external quantum efficiency (~35%) and power efficiency (70 lmW?1) are demonstrated. The cross-evaluation of performance with penicillin devices indicates the significance of ampicillin’s specific molecular structure in improving performance. The detailed investigations demonstrate that ampicillin has superior optoelectronic properties with high potential to contribute extensively in OLEDs and photovoltaics.
关键词： OLEDs,interfacial dipole,bandgap alignment,exciton generation,ampicillin
更新于2025-09-16 10:30:52
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Extremely Efficient Photocurrent Generation in Carbon Nanotube Photodiodes Enabled by a Strong Axial Electric Field
摘要： Carbon nanotube (CNT) photodiodes have potential to convert light into electrical current with high efficiency. However, previous experiments have revealed photocurrent quantum yield (PCQY) well below 100%. In this work, we show that axial electric field increases the PCQY of CNT photodiodes. In optimal conditions our data suggest PCQY > 100%. We studied, both experimentally and theoretically, CNT photodiodes at room temperature using optical excitation corresponding to the S22, S33 and S44 exciton resonances. The axial electric field inside the pn junction was controlled using split gates that are capacitively coupled to the suspended CNT. Our results give new insight into the photocurrent generation pathways in CNTs, and the field dependence and diameter dependence of PCQY.
关键词： scanning photocurrent microscopy,carbon nanotube,carrier multiplication,exciton dissociation
更新于2025-09-16 10:30:52
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Routes for Efficiency Enhancement in Fluorescent TADF Exciplex Host OLEDs Gained from an Electro‐Optical Device Model
摘要： Fluorescence-based organic light-emitting diodes (OLEDs) using thermally activated delayed fluorescence (TADF) have increasingly attracted attention in research and industry. One method to implement TADF is based on an emitter layer composed of an exciplex host and a fluorescent dopant. Even though the experimental realization of this concept has demonstrated promising external quantum efficiencies, the full potential of this approach has not yet been assessed. To this end, a comprehensive electro-optical device model accounting for the full exciton dynamics including triplet harvesting and exciton quenching is presented. The model parameters are fitted to multiple output characteristics of an OLED comprising a TADF exciplex host with a fluorescent emitter, showing an external quantum efficiency of >10%. With the model at hand, an emission zone analysis and a parameter study are performed, and possible routes for further efficiency enhancement are presented.
关键词： exciton dynamics,triplet–triplet annihilation,triplet harvesting,split emission zones,electro-optical simulations
更新于2025-09-16 10:30:52
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Understanding the excitation wavelength dependent spectral shift and large exciton binding energy of tungsten disulfide quantum dots and its interaction with single-walled carbon nanotubes
摘要： Herein, we investigate the origin of excitation wavelength dependent spectral features and high fluorescence quantum yield in fluorescent 2D tungsten disulfide (WS2) quantum dots (QDs) of average size 2.4 nm. The as-prepared WS2 QDs possess high optical bandgap and reasonably high fluorescence quantum yield ~15.4% in the green region without any functionalization. The broad photoluminescence (PL) spectrum consists of multiple peaks owing to emissions from excitonic transitions and surface defect-related transitions. The excitation wavelength-dependent spectral redshift and narrowing of line shape in the PL peak are analyzed carefully, and it is attributed to the selective excitation/recombination of carriers from different energy levels. The temperature-dependent PL analysis yields an exciton binding energy of ~301 meV in the QDs. Furthermore, we study the interaction between fluorescent WS2 QDs and single-walled carbon nanotubes (SWCNTs) and explore the mechanism of systematic quenching of PL of QDs by SWCNTs. The nature of the Stern–Volmer plot is found to be linear, and the time-resolved fluorescence measurements reveal that the quenching follows primarily the static behavior. Our study further reveals that defect sites in SWCNTs primarily act as the binding sites for WS2 QDs and form non-fluorescent complexes for effective quenching of the PL. The strong interaction between the WS2 QDs and the SWCNTs is evidenced from the spectral shift in the X-ray photoelectron spectroscopy and Raman peaks. Our study reveals the origin of excitation wavelength dependent PL emission from WS2 QDs and the nature of the interaction between WS2 QDs and SWCNTs, which are important for their applications in biomedical imaging and sensing, such as surface-enhanced Raman scattering, etc.
关键词： WS2 quantum dots,Fluorescence quenching,Defects,Carbon nanotubes,Exciton binding energy
更新于2025-09-16 10:30:52
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Size-controlled excitonic effects on electronic and optical properties of Sb <sub/>2</sub> S <sub/>3</sub> nanowires
摘要： In this work, the electronic and optical properties of one-dimensional (1D) Sb2S3 nanowires (NWs) with different sizes are investigated using first-principles calculations. The indirect–direct band transition of Sb2S3 NWs can be tuned effectively by the NW size and various uniaxial strains. In the Sb2S3 NWs, the quantum confinement effects result in wider bandgaps while the significantly enhanced electron–hole interaction that is expected to produce excitonic bound states generates a bandgap narrowing. The exciton binding energies for the Sb2S3 NWs are predicted by the effective masses of electrons and holes to lie in the range of 0–1 eV, which are larger than that of bulk Sb2S3, suggesting that excitons in Sb2S3 NWs may bind possible defects to promote luminescence. The size-controlled absorption edge blueshift and redshift of Sb2S3 NWs suggest that Sb2S3 NWs may be promising in the applications of nanoscale light emitting devices.
关键词： optical properties,first-principles calculations,quantum confinement effects,light emitting devices,electronic properties,exciton binding energies,Sb2S3 nanowires
更新于2025-09-16 10:30:52
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Single-particle-picture breakdown in laterally weakly confining GaAs quantum dots
摘要： We present a detailed investigation of different excitonic states weakly con?ned in single GaAs/AlGaAs quantum dots obtained by the Al droplet-etching method. For our analysis we make use of temperature-, polarization-, and magnetic-?eld-dependent μ-photoluminescence measurements, which allow us to identify different excited states of the quantum dot system. Besides that, we present a comprehensive analysis of g-factors and diamagnetic coef?cients of charged and neutral excitonic states in Voigt and Faraday con?guration. Supported by theoretical calculations by the con?guration-interaction method, we show that the widely used single-particle Zeeman Hamiltonian cannot be used to extract reliable values of the g-factors of the constituent particles from excitonic transition measurements.
关键词： g-factors,diamagnetic coefficients,quantum dots,exciton,Zeeman effect
更新于2025-09-16 10:30:52
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Transition Between Exciton-Polariton and Coherent Photonic Lasing in All-Inorganic Perovskite Microcuboid
摘要： All-inorganic lead halide perovskites are ideal platforms to investigate the fundamental physics of the light-matter interactions, due to their strong oscillator strength at room temperature and various microstructures. In this paper, we investigated strong exciton-photon coupling and coherent photonic lasing in a same high-quality self-assembled CsPbBr3 perovskite microcuboid grown by a chemical vapor deposition method. The vacuum Rabi splitting of polariton up to 309 meV, and the exciton-like and photon-like components in low polariton states at different cavity-exciton detuning, were revealed by angle-resolved photoluminescence spectra at room temperature. Moreover, we realized a coherent photonic lasing with a high quality-factor (4153) and narrow linewidth (0.13 nm) in the microcuboid above threshold (16 μJ/cm2), originated from population inversion. Significantly, the interference pattern of the coherent lasing through the Young's double-slit interference method based on far-field Fourier optical system, directly indicate the parity (odd) of the lasing mode and the asymmetric electric-field distribution in the CsPbBr3 microstructure. Our work demonstrates for the first time a transition from the strong coupling regime (vertical Fabry–Pérot oscillation) to weak coupling regime (lateral Fabry–Pérot oscillation) in such self-assembled microcuboid under the competition between gain and internal loss. Based on this mechanism, a considerable promise is expected to enrich the functions of micro-nano structure photoelectric devices by precisely controlling the quality-factor and gain of such microstructure.
关键词： Exciton-polaritons,Young's interference,Perovskite microcuboid,Photonic lasing,Fabry–Pérot microcavity
更新于2025-09-16 10:30:52
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Exciton states in InGaAsP/InP core–shell quantum dots under an external electric field
摘要： The effect of an external electric field on the exciton states of InGaAsP/InP core–shell quantum dots is investigated through the variational method. The effect of the shell thickness, core radius, electric field strength, and material components on the exciton states are analyzed in detail. The numerical results show that the electron and hole energies decrease as the shell thickness or core radius is increased. The Bohr radius is a nonmonotonic function of the shell thickness or core radius, and the change of the exciton binding energy is nonlinear as the shell thickness or core radius is increased. With increasing electric field strength, the Bohr radius increases while the exciton binding energy decreases. The exciton binding energy decreases (increases) as the Ga (As) component is increased.
关键词： Electric field,Core–shell quantum dot,Exciton binding energy
更新于2025-09-16 10:30:52