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Photo-response in 2D metal chalcogenide-ferroelectric oxide heterostructure controlled by spontaneous polarization
摘要： The interplay between free and bound charges in two-dimensional (2D) semiconductor/ferroelectric oxide structures is responsible for the unique opto-electrical properties of these structures. In this study, we vertically combined the 2D layered semiconductors MoS2 (n-type) and WSe2 (p-type) with a ferroelectric oxide (PbTiO3) and found that a ferroelectric polarization induced accumulation or depletion in the layered materials. The heterostructures exhibited polarization-dependent charge distribution and pinched hysteresis. We show that polarization at the interface promoted e?cient charge separation of photo-generated carriers in the 2D layers. Optical control of electrical transport was e?ectively achieved in the MoS2 layers. This study potentially opens up new applications for semiconductor/ferroelectric systems in electronic devices.
关键词： opto-electrical properties,optical control,MoS2,2D semiconductor,ferroelectric oxide,PbTiO3,charge separation,WSe2
更新于2025-09-19 17:13:59
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Role of nitrogen doped carbon quantum dots on CuO nano-leaves as solar induced photo catalyst
摘要： A p-type transition metal oxide, copper oxide (CuO) was modified with nitrogen doped carbon quantum dots (NCQDs) to fabricate an effective CuO/NCQDs solar driven photo catalyst. The fabrication of single phase monoclinic CuO was confirmed by XRD. SEM images showed the leaf like morphology for CuO which appeared rough and densely packed in CuO/NCQDs composites. TEM images of CuO/NCQDs shows slightly distorted nano-leaves with NCQDs dispersed on them. HRTEM of CuO/NCQDs shows fringes with characteristic planes confirming that the addition of NCQDs has not distorted the crystal structure of CuO. SAED of CuO/NCQDs further confirms the crystalline nature of the as synthesized composite photo catalyst by exhibiting bright diffraction rings. These results further supported the XRD data. EDS spectra of NCQDs and CuO/NCQDs confirm the formation of pure nitrogen doped carbon quantum dots and Cu, N, C and O atoms confirming that NCQDs are well incorporated on CuO Nano leaves. UV-Vis spectra showed a slight increase of band gap energies due to quantum confinement effects. PL spectra exhibited decreased photoluminescence intensity indicating suppression of recombination rate. The developed photocatalyst was applied for the degradation of harmful dye methyl orange. The composite catalyst showed superior degradation efficiency as compared to pure CuO nano-leaves attributed to enhanced visible light absorption and better charge separation ability due to introduction of NCQDs.
关键词： solar light catalyst,nitrogen doped quantum dots,charge separation efficiency,quantum confinement effect,CuO nano-leaves
更新于2025-09-19 17:13:59
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Modulating Charge Separation Efficiency of Water Oxidation Photoanodes with Polyelectrolyte‐Assembled Interfacial Dipole Layers
摘要： The charge separation efficiency of water oxidation photoanodes is modulated by depositing polyelectrolyte multilayers on their surface using layer-by-layer (LbL) assembly. The deposition of the polyelectrolyte multilayers of cationic poly(diallyldimethylammonium chloride) and anionic poly(styrene sulfonate) induces the formation of interfacial dipole layers on the surface of Fe2O3 and TiO2 photoanodes. The charge separation efficiency is modulated by tuning their magnitude and direction, which in turn can be achieved by controlling the number of bilayers and type of terminal polyelectrolytes, respectively. Specifically, the multilayers terminated with anionic poly(styrene sulfonate) exhibit a higher charge separation efficiency than those with cationic counterparts. Furthermore, the deposition of water oxidation molecular catalysts on top of interfacial dipole layers enables more efficient photoelectrochemical water oxidation. The approach exploiting the polyelectrolyte multilayers for improving the charge separation efficiency is effective regardless of pH and types of photoelectrodes. Considering the versatility of the LbL assembly, it is anticipated that this study will provide insights for the design and fabrication of efficient photoelectrodes.
关键词： interfacial dipole,polyelectrolyte multilayers,charge separation,photoelectrodes
更新于2025-09-16 10:30:52
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Metal-free carbon nitride with boosting photo-redox ability realized by the controlled carbon dopants
摘要： Metal-free carbon nitride with controlled carbon dopants (ACCN) was synthesized by one-step copolymerization of dicyandiamide (DCD) and ammonium citrate (AC). The obtained ACCN possesses narrower band gap compared to pure graphitic carbon nitride (CN), contributing to broader utilization region of visible light. It exhibits downshifted conduction band and valence band potential with the increased addition of AC. Carbon atoms replace the bridging nitrogen atoms in the framework of ACCN during calcination process, which greatly increase its electrical conductivity and charge separation efficiency. In addition, nitrogen defects and some carbon species linked to the introduced carbon atoms are detected in ACCN. They can also serve as electrons sink to promote the separation of electron-hole pairs. As a consequence, ACCN possesses improved redox ability in the degradation of sulfamethazine (SM2) under visible light. The removal ratio by optimal ACCN achieves 81% in 60 min and its reaction apparent rate constant (0.0277 min?1) is 6.6 times higher than that of CN (0.0042 min?1). Furtherly, the mechanism and reaction process during the photocatalytic degradation are studied specifically. This work provides a facile and green strategy to prepare nonmetal modified CN with boosting photo-redox ability for pollutants treatment.
关键词： g-C3N4,Charge separation,Photocatalysis,Carbon dopants,Pollutants degradation,Ammonium citrate
更新于2025-09-16 10:30:52
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Assessing the energy offset at the electron donor/acceptor interface in organic solar cells through radiative efficiency measurements
摘要： Energy offsets at the electron donor/acceptor interface play an important role in the operation of organic solar cells (OSCs), because their magnitude strongly affects the efficiency of photo-induced charge separation and hence the short-circuit current of a device under illumination. However, quantitative assessment of energy offsets in operating devices remains an open challenge that is still out of the reach of present techniques. Here we show that the ratio of the radiative efficiency (EQEEL) for a blend device to that for the lower bandgap component device (usually a non-fullerene acceptor), namely the EQEEL ratio, can be a strong indicator of the energy offsets in the blend device. In photovoltaic devices based on donors and acceptors with similar backbone structure but varied energy levels, lowering the highest occupied molecular orbital (HOMO) offset increases the open-circuit voltage (VOC) from 0.95 V to 1.05 V, which is consistent with the EQEEL variation trends in the devices. The blend EQEEL approaches that of the emissive low bandgap acceptor when the HOMO of the donor is sufficiently deepened, which at the same time corresponds to a reduction in VOC loss and inefficient photoinduced charge separation. The results suggest that the intrinsic energy loss associated with charge separation can be minimized in practice by minimizing the energy offsets but at the expense of lowering the charge separation efficiency. Statistics from several state-of-the-art material systems reveal that efficient charge generation occurs when the EQEEL ratio is less than 0.1, corresponding to an additional non-radiative voltage loss due to the energy offset of 60 mV. Based on this finding and a modified Shockley–Queisser theory, we estimate an upper thermodynamic efficiency limit for single-junction organic solar cells of about 31%, which is slightly below the Shockley–Queisser limit.
关键词： energy offsets,charge separation,organic solar cells,non-fullerene acceptors,radiative efficiency
更新于2025-09-16 10:30:52
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Plasmonic Ag as electron-transfer mediators in Bi2MoO6/Ag-AgCl for efficient photocatalytic inactivation of bacteria
摘要： Solar-driven photocatalysis undoubtedly represents one of the most promising alternative water disinfection technologies, however, its practical application is still restrained by the fast recombination of carriers. To overcome this limitation, plasmon-induced photocatalytic processes have gained attention due to their extended optical absorption and enhanced charge separation when metal nanoparticles act as co-catalysts. In this work, to enhance the photocatalytic disinfection of Bi2MoO6/AgCl, the formation of plasmonic Ag nanoparticles as electron transfer mediators was promoted on the surface of Bi2MoO6 photocatalysts. Specifically, the co-modified Bi2MoO6/Ag-AgCl photocatalysts were synthesized via a two-step process involving the precipitation of AgCl and photo-reduction of Ag on the Bi2MoO6 surface. It was found that Bi2MoO6/Ag-AgCl photocatalysts exhibited higher photocatalytic disinfection activity under visible light irradiation than those of Bi2MoO6 and Bi2MoO6/AgCl. The photocatalytic mechanism of Bi2MoO6/AgCl could be attributed to the excellent synergistic effect of Ag and AgCl, where plasmonic Ag nanoparticles promote light absorption and work as electron-transfer mediators to transfer electrons from Bi2MoO6 to AgCl, meanwhile AgCl work as interfacial catalytic active sites to product free radicals based on the powerful characterizations, such as PL spectra, photoelectrochemical methodology and theoretical calculations. This work may provide new insights to employ synergistic effect of heterogeneous photocatalysts for improving the catalytic activities in water purification.
关键词： charge separation and transfer,plasmon effect,photocatalytic disinfection,Bi2MoO6 microspheres,Ag
更新于2025-09-16 10:30:52
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Molecular and Energetic Order Dominate the Photocurrent Generation Process in Organic Solar Cells with Small Energetic Offsets
摘要： Minimizing the energetic offset between donor (D) and acceptor (A) in organic solar cells (OSCs) is pivotal to reduce the charge-transfer (CT) loss and improve the open-circuit voltage (Voc). This nevertheless intrigues a disputable topic on the driving force for the charge separation in OSCs with small energetic offsets. The molecular packing geometries in the active layer determine the energetic levels and trap density, while their relationship with driving force is yet seldom considered. Limited by the complicated demixing morphology and inaccurate measurements of energy levels in the prototypical bulk-heterojunction (BHJ) devices, we thereby demonstrate a concise and robust planar-heterojunction model of PM7/N2200 to investigate the origin of driving force for charge generation. It is surprising to note that the device with smaller energy offset shows higher efficiency. Further analysis reveals that bilayer device with short-range packing PM7 exhibits smaller energetic offsets along with less morphological defects and traps compared to its long-range packing counterparts. This molecular packing characteristic diminishes the energetic disorder at the D/A interfaces and inhibits the trap-assisted charge recombination, contributing to the increased short-circuit current (Jsc) and Voc. Our results suggest that the energetic offset actually has limited influence on charge separation, while the synergetic control of molecular and energetic order is vital to the photocurrent generation and energy loss reduction in OSCs.
关键词： energetic offset,organic solar cells,molecular packing,photocurrent generation,charge separation
更新于2025-09-16 10:30:52
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Disorder vs Delocalization: Which Is More Advantageous for High-Efficiency Organic Solar Cells?
摘要： We investigate the combined influence of energetic disorder and delocalization on electron-hole charge-transfer state separation efficiency in donor-acceptor organic photovoltaic systems using an analytical hopping model and Monte Carlo calculations, coupled with an effective mass model. Whereas energetic disorder increases the separation yield at intermediate and low electric fields for low efficiency blends with strongly localized carriers, we find that it reduces dramatically the fill factors and power conversion efficiencies in high efficiency solar cells that require high carrier delocalization within the conjugated segment and high mobility-lifetime product. We further demonstrate that the initial electron-hole distance and thermalization processes play only a minor role in the separation dynamics.
关键词： Charge separation,delocalization,organic photovoltaics,disorder,Monte Carlo simulations
更新于2025-09-12 10:27:22
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Achieving Fast Charge Separation and Low Nonradiative Recombination Loss by Rational Fluorination for High‐Efficiency Polymer Solar Cells
摘要： Four low-cost copolymer donors of poly(thiophene-quinoxaline) (PTQ) derivatives are demonstrated with different fluorine substitution forms to investigate the effect of fluorination forms on charge separation and voltage loss (Vloss) of the polymer solar cells (PSCs) with the PTQ derivatives as donor and a A–DA’D–A-structured molecule Y6 as acceptor. The four PTQ derivatives are PTQ7 without fluorination, PTQ8 with bifluorine substituents on its thiophene D-unit, PTQ9, and PTQ10 with monofluorine and bifluorine substituents on their quinoxaline A-unit respectively. The PTQ8- based PSC demonstrates a low power conversion efficiency (PCE) of 0.90% due to the mismatch in the highest occupied molecular orbital (HOMO) energy levels alignment between the donor and acceptor. In contrast, the devices based on PTQ9 and PTQ10 show enhanced charge-separation behavior and gradually reduced Vloss, due to the gradually reduced nonradiative recombination loss in comparison with the PTQ7-based device. As a result, the PTQ10-based PSC demonstrates an impressive PCE of 16.21% with high open-circuit voltage and large short-circuit current density simultaneously, and its Vloss is reduced to 0.549 V. The results indicate that rational fluorination of the polymer donors is a feasible method to achieve fast charge separation and low Vloss simultaneously in the PSCs.
关键词： voltage loss,nonradiative recombination,low-cost copolymer donors,fluorination,charge separation
更新于2025-09-12 10:27:22
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How does the porphyrin-like vacancy affect the spectral properties of graphene quantum dots? A theoretical study
摘要： By processing graphene quantum dot, an ideal semiconductor material with suitable band gap and higher electron mobility can be obtained. Thus, it has a broad prospect in the application of photoelectric response materials. Here, a graphene defect with porphyrin-like structure is selected to achieve the controlable light absorption. The double five-membered-ring parallel vacancy are based on self-healing properties of popular graphene defects. Aimed to separate exciton and hole more effectively and achieve higher photoelectric conversion efficiency, the occupied orbital and unoccupied orbital of the quantum dot with objected defect structure is taken as orderly dispersion to form an obvious charge separation state under the demonstration with first principles calculation. Most importantly, a real time real space charge separation is calculated by time-dependent ab-initio quantum dynamics based on numerical atomic basis sets. The result shows the specific graphene defects can form an efficient pure graphene photoelectric response medium like porphyrin skeleton, and the vacancy will induce to adjust and control the specific wavelength of the response light and charge separated state manipulably with odevity of number of peripheral carbon rings by the calculation of ultrafast process.
关键词： Charge separation,Time-dependent density functional theory,Graphene defects
更新于2025-09-12 10:27:22