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Carbon quantum dots modified anatase/rutile TiO2 photoanode with dramatically enhanced photoelectrochemical performance
摘要： Titanium dioxide (TiO2) is a promising photoanode material for photoelectrochemical (PEC) water splitting, but the severe bulk recombination of photongenerated carriers, the sluggish oxygen evolution reaction (OER) kinetics and the poor visible light response are the main bottleneck problems. Here, the carbon quantum dots (CQDs) modified anatase/rutile TiO2 photoanode (CQDs/A/R-TiO2) was designed by growth of anatase TiO2 nanothorns on the rutile TiO2 nanorods and further surface modification of CQDs. The results revealed that A/R-TiO2 heterojunction significantly suppressed the bulk recombination of photogenerated carriers. With further incorporation of CQDs into A/R-TiO2, dramatical improvement of OER kinetics and light harvesting were obtained. The bulk charge separation efficiency (ηbulk) and the surface charge injection efficiency (ηsurface) of CQDs/A/R-TiO2 are 1.69 and 5.74 times higher than that of the pristine TiO2 at 0.6 V vs. RHE, respectively. The photocurrent of CQDs/A/R-TiO2 is increased by 11.72 times and the onset potential of CQDs/A/R-TiO2 is negatively shifted by 240 mV.
关键词： Anatase/rutile TiO2 heterojunction,Carbon quantum dots,Bulk and surface charge transfer kinetics,PEC,Light harvesting
更新于2025-09-23 15:19:57
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Impact of Spin Exchange Interaction on Charge Transfer in Dual Polymer Photovoltaic Composites
摘要： Magnetic resonance, relaxation, and dynamic parameters of spin charge carriers photoinitiated in dual polymer composites formed by narrow-bandgap poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(bithiophene)] (F8T2), poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT), poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) copolymers modified with [6,6]-phenyl-C61-butanoic acid methyl ester (PC61BM) as photovoltaic spin subsystem and polyaniline salt doped with para-toluenesulfonic acid (PANI:TSA) as guest spin subsystem were comparatively studied by the direct Light-Induced Electron Paramagnetic Resonance (LEPR) spectroscopy in a wide photon energy and temperature range. Irradiation of dual polymer composite by the photons leads to the formation in its photovoltaic subsystem of polarons and methanofullerene radical anions whose concentration and dynamics are determined by the density and energy of the initiating light photons. A part of such polarons first filled high-energetic spin traps formed in the matrix due to its disordering. A crucial role of exchange interaction between different spin ensembles in the charge excitation, relaxation and transport in multispin narrow-bandgap composites was demonstrated. These processes were interpreted within the framework of hopping of polarons along copolymer chains of photovoltaic subsystems and their exchange interaction with neighboring spin ensembles. Such interaction was shown to facilitate the transfer of charges and inhibits their recombination in multispin dual polymer composites. The distribution of spin density over polymer chains in the dual polymer composites with the π-π-stacked architecture was analyzed in framework of the density functional theory (DFT). It confirmed the transfer of electron spin density between neighboring polymer chains that provokes formation more likely radical pairs in triplet state than singlet one and inhibits their fast geminate recombination. Spin interactions eliminate the selectivity of these systems to the photon energy, extends the range of optical photons they are absorbed and, therefore, increases their efficiency to converse the light energy. Handling electronic properties via intra- and inter-subsystem spin interactions in such multispin composites allows to create on their base a more efficient and functional electronic and spintronic elements.
关键词： LEPR spectroscopy,DFT,charge transfer,spin exchange interaction,dual polymer photovoltaic composites
更新于2025-09-23 15:19:57
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CuIn-ethylxanthate a a??versatile precursora?? for photosensitization of graphene-quantum dots and nanocatalyzed synthesis of imidazopyridines with ideal green chemistry metrics
摘要： Recently, the development of hybrid nano catalyst involving earth abundant transition metals for photosensitization and multi-component reaction in industry and academia has been a matter of intense study. Such hybridized catalytic systems minimize the production cost and acts as a bridged system by diversifying the application in different areas. In the present study copper indium ethylxanthate was used as a versatile precursor for synthesis of colloidal chalcopyrite phase copper indium sulphide (CC-CIS NPs) in photosensitization of graphene quantum dots and reusable powdered wurzite phased copper indium sulphide nanoparticles (PW-CIS500 NPs) for selective and efficient single pot sustainable synthesis of substituted imidazopyridines via A3 coupling strategy of an aldehyde, amine and alkyne. The material was characterized by various spectroscopic techniques viz HR-TEM, PXRD, FESEM, elemental mapping studies, UV visible spectroscopy, photoluminescence, XPS, BET and ICP-OES/MS etc. Quenching of photoluminescence intensity of colloidal CuInS2 on anchoring the graphene quantum dots (GQDs) was confirmed by photosensitization of GQDs via efficient charge transfer in CIS-GQD interface. On the other hand, the PW-CIS500 NCs catalyzed A3 coupling strategy demonstrates the high catalytic efficiency for A3 coupling reaction giving substituted imidazopyridines without losing its activity and could be recycled with a total turnover number of > 210, good E-factor of 0.13 and high RME of 88%.
关键词： multicomponent reactions,heterogenous catalysis,copper indium sulphide,copper indium ethylxanthate,imidazopyridines,graphene quantum dots,charge transfer
更新于2025-09-23 15:19:57
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Tuning Plasmonic Coupling from Capacitive to Conductive Regimes via Atomic Control of Dielectric Spacing
摘要： The gap length between plasmonic nanoparticles determines the strength of the optical coupling that results in electromagnetic field enhancement for spectroscopic and other applications. Although gap plasmon resonances have been the focus of increasing research interest, experimental observations have primarily been limited to the coupling of spherical nanoparticles that may not provide clear spectral contrast of the optical response as the interaction evolves from capacitive to charge transfer with the gap size decreasing to subnanometer. Here, by taking advantage of the sharp plasmon resonances of colloidal gold nanorods coupled to gold film, we present the spectral evolution of gap plasmon resonance as the particle-film spacing varies from over 30 nm to the touching limit. We find that, the capacitive gap plasmon resonance of the coupled system red shifts and narrows continuously until it vanishes at the quantum tunneling limit, in contrast to the nonlocal and Landau damping effects that are expected to result in relative blue shifting and spectral broadening. When the spacer thickness is further decreased, high order cavity modes appear, and eventually single peak broad resonances that are characteristic of tunneling and direct contact particle-film interaction emerge. The experimental observations show that nanorods are better suited for creating cavity plasmon resonances with high quality factor, and the spectral contrast at the transition provides clarity to develop improved theoretical modeling of optical coupling at subnanometer gap lengths.
关键词： atomic layer deposition,tunneling,plasmon coupling,Particle on metal film,cavity modes,charge transfer,gold nanorods
更新于2025-09-23 15:19:57
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The Role of Dipole Moment in Two Fused-Ring Electron Acceptors with One Polymer Donor based Ternary Organic Solar Cells
摘要： Fused-ring electron acceptors (FREAs) based ternary organic solar cells (OSCs) have made significant progress and attracted considerable attention due to their simple device architecture and broad absorption range in devices. There are three key parameters that need to be fine-tuned in ternary OSCs including absorption, energy level and morphology in order to realize high efficiencies. Herein, a series of FREAs with diverse electron-rich cores or electron-deficient terminals are developed and rationally combined to achieve high performance ternary OSCs. A new factor of dipole moment of FREAs’ terminals is unveiled and its working mechanism has been thoroughly investigated by systematical studying of six ternary OSCs. These ternary blends all exhibit complementary absorptions and cascade energy levels, which can facilitate efficient light-harvesting and charge transfer. Additionally, the morphological effects on ternary OSCs are eliminated through comparative studies while demonstrating distinctively different performance. The preliminary results show that compatible dipole moment between two FREAs is critical in ternary blends. Specifically, the performance of the ternary system with two FREAs having quite different dipole moment terminals is worse than that with similar terminal dipole moments. The pair with larger difference in dipole moment will also negatively impact device performance. This interesting phenomenon is likely due to that very different dipole moments of terminals in FREAs can significantly decrease the electron mobility as well as induce unbalanced hole/electron transport. Consequently, it results in increased charge recombination and reduced charge collection efficiency. This finding demonstrates that dipole moment of FREAs should be taken into account in designing ternary OSCs.
关键词： ternary organic solar cells,morphology,dipole moment,charge transfer,Fused-ring electron acceptors
更新于2025-09-23 15:19:57
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Reduced Nonradiative Voltage Loss in Terpolymer Solar Cells
摘要： The dissociation of hybrid local-charge transfer excitons (LE-CT) in efficient bulk-heterojunction non-fullerene solar cells contributes to reduced non-radiative photovoltage loss, a mechanism that still remains unclear. Herein, we studied the energetic and entropic contribution in the hybrid LE-CT exciton dissociation in devices based on a conjugated terpolymer. Compared to reference devices based on ternary blends, the terpolymer devices demonstrated a significant reduction of the non-radiative photovoltage loss, regardless of the acceptor molecule, be it fullerene or non-fullerene. Fourier transform photocurrent spectroscopy revealed a significant LE-CT character in the terpolymer-based non-fullerene solar cells. Temperature-dependent hole mobility and photovoltage confirm that entropic and energetic effects contribute to the efficient LE-CT dissociation. The energetic disorder value measured in the fullerene- or nonfullerene-based terpolymer devices suggested that this entropic contribution came from the terpolymer, a signature of higher disorder in copolymers with multiple aromatic groups. This gives new insight into the fundamental physics of efficient LE-CT exciton dissociation with smaller non-radiative recombination loss.
关键词： non-radiative photovoltage loss,terpolymer solar cells,entropic and energetic effects,hybrid local-charge transfer excitons,Fourier transform photocurrent spectroscopy
更新于2025-09-23 15:19:57
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High‐Performance Photoinduced Memory with Ultrafast Charge Transfer Based on MoS <sub/>2</sub> /SWCNTs Network Van Der Waals Heterostructure
摘要： Photoinduced memory devices with fast program/erase operations are crucial for modern communication technology, especially for high-throughput data storage and transfer. Although some photoinduced memories based on 2D materials have already demonstrated desirable performance, the program/erase speed is still limited to hundreds of micro-seconds. A high-speed photoinduced memory based on MoS2/single-walled carbon nanotubes (SWCNTs) network mixed-dimensional van der Waals heterostructure is demonstrated here. An intrinsic ultrafast charge transfer occurs at the heterostructure interface between MoS2 and SWCNTs (below 50 fs), therefore enabling a record program/erase speed of ≈32/0.4 ms, which is faster than that of the previous reports. Furthermore, benefiting from the unique device structure and material properties, while achieving high-speed program/erase operation, the device can simultaneously obtain high program/erase ratio (≈106), appropriate storage time (≈103 s), record-breaking detectivity (≈1016 Jones) and multibit storage capacity with a simple program/erase operation. It even has a potential application as a flexible optoelectronic device. Therefore, the designed concept here opens an avenue for high-throughput fast data communications.
关键词： van der Waals heterostructures,program/erase performance,photoinduced memory,ultrafast charge transfer
更新于2025-09-23 15:19:57
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Analysis of the charge transfer and separation in electrically doped organic semiconductors by electron spin resonance spectroscopy
摘要： We investigated the charge generation mechanism of electrically doped organic semiconductors (OSs) by electron spin resonance (ESR) analysis. ESR spectroscopy was used to successfully evaluate the radical density of p-doped OSs to estimate the charge transfer efficiency (CTE) of various doped systems. The results showed that the CTE is efficient close to 100% if the dopant molecules are homogenously dispersed and the energy difference (?E) between the highest occupied molecular orbital (HOMO) level of the host molecule and lowest unoccupied molecular orbital (LUMO) level of the p-dopant is large. The charge separation efficiency to form free carriers from the radicals is rather low (less than 12% in this study) and is a dominant factor controlling the charge generation efficiency (CGE). An organic dopant molybdenum tris[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] turns out to be an efficient dopant with the CGE of 9.7% due to high CTE originating from homogenous dispersion of the organic p-dopants and low LUMO level, i.e., large ?E.
关键词： charge generation efficiency,p-dopant,charge transfer,electron spin resonance spectroscopy,Organic semiconductors,charge separation
更新于2025-09-19 17:15:36
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Synergy of light harvesting and energy transfer as well as short-range charge shift reactions in multicomponent conjugates
摘要： We report herein on the design, the synthesis, and the characterization of a panchromatic, charge stabilizing electron donor–acceptor conjugate: (BBPA)3–ZnPor–ZnPc–SubPc 1. Each component, that is, bis(biphenyl)phenylamine (BBPA), Zn(II) porphyrin (ZnPor), Zn(II) phthalocyanine ZnPc, and subphthalocyanine (SubPc), has been carefully chosen and modified to enable a cascade of energy and charge transfer processes. On one hand, ZnPor, has been functionalized with three electron-donating BBPA as primary and secondary electron donors and to stabilize the final charge-separated state, and, on the other hand, a perfluorinated SubPc has been selected as ultimate electron acceptor. In addition, the ZnPc unit contains several trifluoromethylphenyl moieties to match its energy levels to those of the other components. In fact, irradiation of the heteroarray 1 triggers a cascade of light harvesting across the entire visible range, unidirectional energy transfer, exergonic charge separating, and short-range charge shifting to afford a (BBPA)3(cid:129)+–ZnPor–ZnPc–SubPc(cid:129)? charge-separated state. The lifetime of the latter reaches well into the range of tens of nanoseconds with a 14% quantum yield.
关键词： charge stabilizing,light harvesting,panchromatic,charge transfer,energy transfer,porphyrinoids,electron donor–acceptor conjugate
更新于2025-09-19 17:15:36
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Nanostructuring Confinement for Controllable Interfacial Charge Transfer
摘要： Carbon nanostructures supported semiconductors are common in photocatalytic and photoelectrochemical applications, as it is expected that the nanoconductors can improve the spatial separation and transport of photogenerated charge carriers. Transfer of charge carriers through the carbon-semiconductor interface is the key electronic process, which determines the role of charge separation channels, and is sensitively influenced by band structures of the semiconductor near the contacts. Usually, this electronic process suffers from excessive energy dissipation by thermionic emission, which will undesirably prevent the interfacial charge transfer and eventually aggravate the recombination of photogenerated charge carriers. Unfortunately, this critical issue has hardly been consciously considered. Here, ultrathin dopant-free tunneling interlayers coated on the surface of graphene and sandwiched between the carbon sheets and the semiconductor nanostructures are adopted as a model system to demonstrate energy saving for the interfacial charge transfer. The nanostructuring confinement of band bending within the ultrathin interlayers in contact with the graphene sheets effectively narrows the width of the potential barriers, which enables tunneling of a substantial number of photogenerated electrons to the co-catalysts without unduly consuming energy. Besides, the dopant-free tunneling interlayers simultaneously block the transferred electrons in the sandwiched graphene sheets from leakage.
关键词： nanostructuring confinement,thermionic emission,electron tunneling,charge transfer,charge transport
更新于2025-09-19 17:15:36