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Efficient NDT small molecule solar cell with high fill factor by pendant group engineering
摘要： Three naphthodithiophene (NDT)-based small molecules, bearing hexyl- (NDT-Hex), null (NDT) and fluorene (NDT-F) substituents at the β-position of the thiophene vertically conjugated to the NDT core, were designed and synthesized. The photovoltaic effect of engineered NDT molecules was investigated with detailed characterization on optical absorption, electronic energy levels, blend morphology, carrier mobility and photovoltaic performance conducted. It shows that the hexyl-substitution enhances the morphological tunability for NDT molecules, which contributes to achieve promising power conversion efficiency (PCE) with high fill factor (FF). The optimized solar cells based on NDT-Hex:PC71BM blends obtains a PCE of 6.7% with an FF of 0.717 and it reaches 8.6% with an FF of 0.638 if a non-fullerene molecular acceptor, NBDTP-Fout, was adopted to blend with NDT-Hex. Both FF are among the top ones of respective kind of solar cells based on NDT small molecule. The work demonstrates a feasible morphology-tuning method toward efficient organic solar cells with high FF.
关键词： morphology-tuning,naphthodithiophene,small molecule solar cells,high fill factor,pendant group engineering
更新于2025-09-23 15:19:57
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Field Squeezing in a Quantum-Dot Molecule Jaynes-Cummings Model
摘要： We investigate the field squeezing in a system composed of an initial coherent field interacting with two quantum dots coupled by electron tunneling. An approximate quantum-dot molecule Jaynes-Cummings model describing the system is given, and the effects of physical quantities, such as the temperature, phonon-electron interaction, mean photon number, field detuning, and tunneling-level detuning, are discussed in detail.
关键词： Jaynes-Cummings model,phonon-electron interaction,electron tunneling,quantum-dot molecule,field squeezing
更新于2025-09-23 15:19:57
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Room-Temperature Optical Picocavities below 1 nm <sup>3</sup> Accessing Single-Atom Geometries
摘要： Reproducible con?nement of light on the nanoscale is essential for the ability to observe and control chemical reactions at the single-molecule level. Here we reliably form millions of identical nanocavities and show that the light can be further focused down to the subnanometer scale via the creation of picocavities, single-adatom protrusions with angstrom-level resolution. For the ?rst time, we stabilize and analyze these cavities at room temperatures through high-speed surface-enhanced Raman spectroscopy on speci?cally selected molecular components, collecting and analyzing more than 2 million spectra. Data obtained on these picocavities allows us to deduce structural information on the nanoscale, showing that thiol binding to gold destabilizes the metal surface to optical irradiation. Nitrile moieties are found to stabilize picocavities by 10-fold against their disappearance, typically surviving for >1 s. Such constructs demonstrate the accessibility of single-molecule chemistry under ambient conditions.
关键词： picocavities,surface-enhanced Raman spectroscopy,single-molecule chemistry,optical con?nement,nanocavities
更新于2025-09-23 15:19:57
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Fluorescence anisotropy imaging of a polydiacetylene photopolymer film
摘要： UV-illumination of phase-separated surfactant films prepared from mixtures of photopolymerizable 10,12-pentacosadiynoic acid and perfluorotetradecanoic acid results in the formation of fluorescent polydiacetylene fibers and aggregates. In this work, the orientation of polymer strands that comprise the resulting photopolymer structures has been probed using fluorescence anisotropy imaging in combination with defocused single-molecule fluorescence imaging. Imaging experiments indicate the presence of significant fiber-to-fiber heterogeneity, as well as anisotropy within each fiber (or aggregate), with both of these properties changing as a function of film preparation conditions. This anisotropy can be attributed to various alignments of the constituent polymer strands that comprise the larger fibers and aggregates. Intriguingly, when using defocused imaging, fiber images consisted of a series of discrete 'doughnut' fluorescence emission patterns, which exhibited intermittent on–off blinking behavior; both of these properties are characteristic of individual emission transition dipoles (single molecules). Further, all of the individual emission transition dipoles had a uniform orientation with respect to the axis of the fiber, indicating a common orientation of discrete emitters in the larger polymer fiber. The implications of these results for future studies of the electronic properties of conjugated polymers in larger macroscopic systems are noted.
关键词： 12-pentacosadiynoic acid,polydiacetylene,fluorescence anisotropy imaging microscopy,single-molecule spectroscopy,10,Langmuir film
更新于2025-09-19 17:15:36
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Multistimuli-responsive small-molecule compound with aggregation-induced emission enhancement characteristics: preparation, properties and applications
摘要： A novel multifunction luminescent small-molecule compound with hydrophilic chains was successfully designed and synthesized, which exhibited aggregation-induced emission enhancement (AIEE) characteristics. Even more interesting, it exhibited responsive behavior to temperature, pH and UV irradiation. In aqueous solution, its luminescence intensity showed temperature sensitivity. Initially, its luminescence intensity decreased slightly with an increase in temperature, which was enhanced greatly when the temperature increased to its lower critical solution temperature (LCST). With a further increase in temperature, there was a significant decline in its luminescence intensity. Additionally, it showed different pH and UV irradiation responsive behaviors in water and THF solution. In THF solution, its luminescence intensity was enhanced greatly with the addition of alkali, but it decreased with an increase in UV irradiation time. In aqueous solution, its luminescence intensity was enhanced slightly and its LCST decreased first and then increased with the addition of alkali. However, its luminescence intensity increased with an increase in UV irradiation time. The prepared small-molecule compound could also be used as a rewritable material with solid alkali or alkali solution used as ink and ordinary paper adsorbed with our prepared small-molecule compound used as rewritable paper.
关键词： small-molecule compound,rewritable material,temperature sensitivity,pH responsive,multistimuli-responsive,aggregation-induced emission enhancement,UV irradiation responsive
更新于2025-09-19 17:15:36
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Dependance of Poly(acrylic acid) Interfacial Adhesion on the Nanostructure of Electrodeposited ZnO Films
摘要： Understanding the impact of the intricate morphology and surface chemistry of ZnO nanorod arrays on their interactions with polyelectrolyte polymers is crucial for the development of nascent ZnO-based adhesion-promoting materials. AFM based Single Molecule Force Spectroscopy (SMFS) was applied for the analysis of the adsorption of poly(acrylic acid) (PAA) on zinc oxide (ZnO) film covered stainless steel substrates in aqueous electrolytes at pH 7. Based on the electrodeposition process, the morphology of zinc oxide films could be varied ranging from platelet-like crystals to nanorods. This approach allowed for the morphology dependent analysis of macromolecular adsorption processes on complex ZnO nanostructures which have diverse applications in the field of adhesion-promoting thin films. The surface chemical composition, as determined by X-ray photoelectron spectroscopy, could be correlated to the AFM-based desorption studies. Only equilibrium desorption events (plateaus), centered at 42 pN, were observed on mirror polished, preconditioned stainless steel. However, for platelet-like ZnO films, the poly(acrylic acid) desorption showed a mixture of rupture events (mean rupture forces of about 350 pN) and equilibrium desorption, while ZnO nanorod structures showed solely rupture events with mean rupture forces of about 1300 pN. These results indicate that simultaneous multiple ruptures of carboxylate-zinc bonds occur due to the macromolecular coordination of poly(acrylic acid) to the ZnO nanorods. The analysis of the interfacial adhesion processes is further supported by the dwell time dependence of desorption processes.
关键词： poly(acrylic acid),Single Molecule Force Spectroscopy (SMFS),worm like chain (WLC) model,stainless steel,zinc oxide (ZnO),electrochemical deposition,molecular adhesion,adsorption free energy
更新于2025-09-19 17:15:36
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Many-body States Description of Single-molecule Electroluminescence Driven by Scanning Tunneling Microscope
摘要： Electron transport and optical properties of a single molecule in contact with conductive materials have attracted considerable attention owing to their scientific importance and potential applications. With recent progresses of experimental techniques, especially by the virtue of scanning tunneling microscope (STM)-induced light emission, where the tunneling current of the STM is used as an atomic-scale source for induction of light emission from a single molecule, it becomes possible to investigate single-molecule properties at sub-nanometer spacial resolution. Despite extensive experimental studies, the microscopic mechanism of electronic excitation of a single molecule in STM-induced light emission is yet to be clarified. Here we present a formulation of single-molecule electroluminescence driven by electron transfer between a molecule and metal electrodes based on a many-body state representation of the molecule. The effects of intra-molecular Coulomb interaction on conductance and luminescence spectra are investigated using the nonequilibrium Hubbard Green's function technique combined with first-principles calculations. We compare simulation results with experimental data and find that the intra-molecular Coulomb interaction is crucial for reproducing recent experiments for a single phthalocyanine molecule. The developed theory provides a unified description of both electron-transport and optical properties of a single molecule in contact with metal electrodes driven out of equilibrium, and thereby it contributes to a microscopic understanding of optoelectronic conversion in single molecules on solid surfaces and in nanometer-scale junctions.
关键词： Single molecule luminescence,exciton formation,nonequilibrium Hubbard Green's function technique,time-dependent density functional theory (TDDFT),scanning tunneling microscope-induced light emission,Vibronic interaction
更新于2025-09-19 17:15:36
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Monitoring of Nonadiabatic Effects in Individual Chromophores by Femtosecond Double-Pump Single-Molecule Spectroscopy: A Model Study
摘要： We explore, by theoretical modeling and computer simulations, how nonadiabatic couplings of excited electronic states of a polyatomic chromophore manifest themselves in single-molecule signals on femtosecond timescales. The chromophore is modeled as a system with three electronic states (the ground state and two non-adiabatically coupled excited states) and a Condon-active vibrational mode which, in turn, is coupled to a harmonic oscillator heat bath. For this system, we simulate double-pump single-molecule signals with fluorescence detection for different system-field interaction strengths, from the weak-coupling regime to the strong-coupling regime. While the signals are determined by the coherence of the electronic density matrix in the weak-coupling regime, they are determined by the populations of the electronic density matrix in the strong-coupling regime. As a consequence, the signals in the strong coupling regime allow the monitoring of nonadiabatic electronic population dynamics and are robust with respect to temporal inhomogeneity of the optical gap, while signals in the weak-coupling regime are sensitive to fluctuations of the optical gap and do not contain information on the electronic population dynamics.
关键词： nonadiabatic dynamics,strong-field regime,weak-field regime,single-molecule spectroscopy
更新于2025-09-19 17:15:36
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Growth and Chemical Modification of Silicon Nanostructures Templated in Molecule Corrals: Parallels with the Surface Chemistry of Single Crystalline Silicon
摘要： Molecule corrals having diameters of 30 – 50 nm were created on highly oriented pyrolytic graphite (HOPG) using cesium ion bombardment. The molecule corrals were used as templates to grow silicon nanostructures by physical vapor deposition (PVD). The nanostructures could be grown with control over geometry (rings and mesas), and size distribution. In addition, transmission electron microscopy (TEM) results suggest that the silicon nanostructures are most likely polycrystalline. The chemical modification of these silicon nanostructures with nitrobenzene was compared to that of clean and hydrogen-terminated single crystalline silicon. X-ray photoelectron spectroscopy (XPS) of the modified nanostructures showed peaks located at 398.9 eV, 400.4 eV, and 402.1 eV for the N 1s region, which are consistent with those observed on a Si(100) single crystal. The chemical modification was further characterized by the presence of nitrogen-containing peaks in TOF-SIMS spectra. We conclude that the reaction of nitrobenzene on silicon nanostructures provides evidence that the reactivity of the nanostructures is similar to that of hydrogen-terminated Si(111) and Si(100).
关键词： molecule corrals,functionalized silicon,silicon nanoparticle,chemical modification,template,surface modification
更新于2025-09-19 17:15:36
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Small molecule donor based on alkoxylated benzothiadiazole unit: Synthesis and photovoltaics properties
摘要： Two small molecule donors (namely BTRO and BTCN) based on the benzothiadiazole unit were synthesized in this study. In comparison to BTRO, BTCN has a narrower absorption spectrum, however, BTCN has better crystallinity, higher carrier mobility, and better light absorption that is complementary to IDIC-4F. Non-fullerene all small molecule organic solar cells (SM-OSCs) based on BTCN: IDIC-4F exhibited a power conversion efficiency (PCE) of 4.62% with short circuit current density (Jsc) of 11.46 mA/cm2, open-circuit voltage (Voc) of 0.89 V, and fill factor (FF) of 0.45. In contrast, non-fullerene SM-OSCs based on BTRO: IDIC-4F showed PCE, Jsc, Voc, and FF values of 4.08%, 11.04 mA/cm2, 0.91 V, and 0.41, respectively. Our results show that benzothiadiazole is a very good acceptor unit for regulating the absorption and energy levels of non-fullerene SM-OSCs.
关键词： benzothiadiazole,all small molecule organic solar cells,non-fullerene,small molecule donor
更新于2025-09-19 17:13:59