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Engineering Charge-Transfer States for Efficient, Low-Energy-Loss Organic Photovoltaics
摘要： Charge transfer (CT) between donors and acceptors following photoexcitation of organic photovoltaics (OPVs) gives rise to bound electron–hole pairs across the donor–acceptor interface, known as CT states. While these states are essential to charge separation, they are also a source of energy loss. As a result of reduced overlap between electron and hole wavefunctions, CT states are influenced by details of the film morphology and molecular structure. Here, we describe several important strategies for tuning the energy level and dynamics of the CT state and approaches that can enhance their dissociation efficiency into free charges. Furthermore, we provide an overview of recent physical insights into the key parameters that significantly reduce the Frenkel-to-CT energy offset and recombination energy losses while preserving a high charge-generation yield. Our analysis leads to critical morphological and molecular design strategies for achieving efficient, low-energy-loss OPVs.
关键词： molecular structure,energy loss,organic photovoltaics,charge transfer states,film morphology
更新于2025-09-12 10:27:22
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Perylene Diimide based Organic Photovoltaics with Slot-Die Coated Active Layers from Halogen-Free Solvents in Air at Room Temperature
摘要： Herein, we investigate the role of processing solvent additives on the formation of polymer-perylene diimide bulk-heterojunction active layers for organic photovoltaics using both spin-coating and slot-die coating methods. We compare the effect of 1,8-diiodooctane (DIO) and diphenyl ether (DPE) as solvent additives on the aggregation behavior of the non-fullerene acceptor tPDI2N-EH in neat films and blended films with the benzodithiophene-quinoxaline (BDT-QX, QX-3) donor polymer, processed from toluene in air. DIO-processing crystallizes the tPDI2N-EH acceptor and leads to decreased solar cell performance. DPE-processing has a more subtle effect on the bulk-heterojunction morphology and leads to improved solar cell performance. Comparing spin vs. slot-die coating methods, the effect of DPE is prominent for slot-die coated active layers. While similar device power conversion efficiencies are achieved with active layers coated with both methods (ca. 7.3% vs. 6.5%), the use of DPE improves film quality when the slot-die coating method is employed.
关键词： Organic photovoltaics,Halogen-free processing,Perylene diimide,Slot-die coating,Solvent additive,Diphenyl ether,Quinoxaline,Morphology control
更新于2025-09-12 10:27:22
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The Effects of Laser Parameters and the Ablation Mechanism in Laser Ablation of C/SiC Composite
摘要： The e?ects of laser parameters and the ablation mechanism in laser ablation of a carbon ?ber reinforced silicon carbide (C/SiC) composite are investigated in the present study. Six di?erent power densities are provided, as well as six levels of pulse numbers, and then ablation experiments are conducted for the C/SiC composite, induced by a pulsed laser. Based on the experimental results, the characteristics of surface morphology and ablation behavior are discussed. It is revealed that the surface morphology of the C/SiC composite under laser irradiation usually includes three regions: the center region, the transition region, and the border region. With the increase of laser power density, the ablation of the center region becomes severe, surface cracks occur, and more spherical SiC particles are found in the transition region. As for scenarios involving multiple pulses, the damage occurs in the center region at low power density limits, within the ?rst two layers below the surface. However, if the power density is relatively high, an ablation pit occurs in the center region when the pulse number is larger than 50. Meanwhile, the transition region and the border region diminish with increase of the pulse number. It is noted that both the power density and pulse number have noticeable e?ects on surface morphology and ablation behavior during laser ablation, which is helpful for material design and performance evaluation of C/SiC composites.
关键词： Surface morphology,C/SiC composite,Ablation mechanism,Laser ablation,Scanning electron microscopy (SEM)
更新于2025-09-12 10:27:22
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Influence of Semiconductor Morphology on Photocatalytic Activity of Plasmonic Photocatalysts: Titanate Nanowires and Octahedral Anatase Nanoparticles
摘要： Octahedral anatase particles (OAP) with eight exposed and thermodynamically most stable (101) facets were prepared by an ultrasonication-hydrothermal (US-HT) reaction from potassium titanate nanowires (TNW). The precursor (TNW) and the product (OAP) of US-HT reaction were modi?ed with nanoparticles of noble metals (Au, Ag or Pt) by photodeposition. Samples were characterized by X-ray di?raction (XRD), X-ray photoelectron spectroscopy (XPS), di?use re?ectance spectroscopy (DRS), scanning transmission electron microscopy (STEM) and time-resolved microwave conductivity (TRMC). The photocatalytic activity was investigated in three reaction systems, i.e., anaerobic dehydrogenation of methanol and oxidative decomposition of acetic acid under UV/vis irradiation, and oxidation of 2-propanol under vis irradiation. It was found that hydrogen liberation correlated with work function of metals, and thus the most active were platinum-modi?ed samples. Photocatalytic activities of bare and modi?ed OAP samples were much higher than those of TNW samples, probably due to anatase presence, higher crystallinity and electron mobility in faceted NPs. Interestingly, noble metals showed di?erent in?uence on the activity depending on the semiconductor support, i.e., gold-modi?ed TNW and platinum-modi?ed OAP exhibited the highest activity for acetic acid decomposition, whereas silver- and gold-modi?ed samples were the most active under vis irradiation, respectively. It is proposed that the form of noble metal (metallic vs. oxidized) as well as the morphology (well-organized vs. uncontrolled) have a critical e?ect on the overall photocatalytic performance. TRMC analysis con?rmed that fast electron transfer to noble metal is a key factor for UV activity. It is proposed that the e?ciency of plasmonic photocatalysis (under vis irradiation) depends on the oxidation form of metal (zero-valent preferable), photoabsorption properties (broad localized surface plasmon resonance (LSPR)), kind of metal (silver) and counteraction of “hot” electrons back transfer to noble metal NPs (by controlled morphology and high crystallinity).
关键词： silver,platinum,gold,photocatalyst morphology,faceted titania,morphology-governed activity,plasmonic photocatalysis,octahedral particle,titanate nanowire,noble metal
更新于2025-09-11 14:15:04
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Skin and subcutaneous fat morphology alterations under the LED or laser treatment in rats in vivo
摘要： The main objective of this work is to quantify the dynamic/photothermal treatment by using visible LED and NIR laser irradiation through the skin of subcutaneous fat in vivo followed up by tissue sampling and histology. The optical method may provide reduction of regional or site-specific accumulations of abdominal or subcutaneous adipose tissue precisely and least-invasively by inducing cell apoptosis and controlled necrosis of fat tissue. As photo-dynamic/photothermal adipose tissue sensitizers Brilliant Green (BG) or Indocyanine Green (ICG) dyes were injected subcutaneously in rats. The CW LED device (625 nm) or CW diode laser (808 nm) were used as light sources, respectively. Biopsies of skin together with subcutaneous tissues were taken for histology. The combined action BG-staining and LED-irradiation (BG + LED) or ICG-staining and NIR-laser irradiation (ICG + NIR) causes pronounced signs of damage of adipose tissue characterized by a strong stretching, thinning, folding and undulating of cell membranes and appearance of necrotic areas. As a posttreatment after 14 days only connective tissue was observed at the site of necrotic areas. The data obtained are important for safe light treatment of site-specific fat accumulations, including cellulite. This work provides a basis for the development of fat lipolysis technologies and to move them to clinical applications.
关键词： visible light,laser,optical microscopy,fat morphology,skin,subcutaneous adipose tissue,photodynamic and photothermal treatment,LED,Brilliant Green,NIR,Indocyanine Green (ICG)
更新于2025-09-11 14:15:04
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Surpassing the 10% efficiency milestone for 1-cm2 all-polymer solar cells
摘要： Naphthalenediimide-based n-type polymeric semiconductors are extensively used for constructing high-performance all-polymer solar cells (all-PSCs). For such all-polymer systems, charge recombination can be reduced by using thinner active layers, yet suffering insufficient near-infrared light harvesting from the polymeric acceptor. Conversely, increasing the layer thickness overcomes the light harvesting issue, but at the cost of severe charge recombination effects. Here we demonstrate that to manage light propagation within all-PSCs, a thick bulk-heterojunction film of approximately 350 nm is needed to effectively enhance photo-harvesting in the near-infrared region. To overcome the severe charge recombination in such a thick film, a non-halogenic additive is used to induce a well-ordered micro-structure that inherently suppresses recombination loss. The combined strategies of light management and delicate morphology optimization lead to a promising efficiency over 10% for thick-film all-PSCs with active area of 1 cm2, showing great promise for future large-scale production and application of all-PSCs.
关键词： all-polymer solar cells,light management,naphthalenediimide,thick-film,morphology optimization
更新于2025-09-11 14:15:04
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Effects of laser-assisted grinding on surface integrity of zirconia ceramic
摘要： Zirconia ceramics has an important position in the field of biomaterials because of excellent mechanical properties. Because of abrasive resistance and hardness, conventional machining of zirconia ceramic is difficult and time-consuming. A nontraditional hybrid laser-assisted grinding (LAG) system combining laser and cubic boron nitride (CBN) grinding wheel was developed for machining zirconia ceramic. This hybrid system utilizes the outstanding thermostability of zirconia ceramic: The material present on the cutting path is rapidly removed by local laser heating and grinding wheel. A combined theoretical and experimental study was performed to evaluate different modes of machining of zirconia ceramic. The machining parameters were predicted by numerical analysis. The surface quality, surface morphology, and subsurface damage of zirconia ceramic specimens were analyzed and compared. The results show that LAG can easily achieve ductile regime grinding in the same machine tool. Compared with conventional grinding, the surface integrity of zirconia ceramic was significantly improved by the LAG process. LAG could achieve ductile regime grinding with a large depth-of-cut. It changes the machinability of zirconia ceramic.
关键词： Surface quality,Surface morphology,Laser-assisted grinding,Zirconia ceramic,Subsurface damage
更新于2025-09-11 14:15:04
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Amorphous Polymer Acceptor Containing B ← N Units Matches Various Polymer Donors for All-Polymer Solar Cells
摘要： Polymer acceptors for high-efficiency all-polymer solar cells (all-PSCs) are generally semicrystalline. In this manuscript, we report an amorphous polymer acceptor, which matches well with a variety of polymer donors to produce efficient all-PSCs. The amorphous polymer acceptor (rr-PBN) is a regiorandom polymer consisting of alternating asymmetric B←N bridged thienylthiazole (BNTT) unit and pyridine-flanked diketopyrrolopyrrole (PyDPP) unit. It is amorphous in thin film because of its regiorandom structure and the large steric hindrance. rr-PBN shows deep LUMO/HOMO energy levels of ?3.71/?5.81 eV, strong sunlight harvesting capability and high electron mobility of 2.20 × 10?4 cm2 V?1 s?1. As a polymer acceptor, rr-PBN matches well with three commercially available polymer donors, J71, PTB7-Th, and PffBT4T-2OD to give excellent percolating bicontinuous network morphology in all-PSCs. We propose that the crystallization of polymer donors governs the film-forming process and dominates the phase separation morphology, leading to good phase separation morphology. The all-PSC devices all show power conversion efficiencies (PCEs) of 5.2?6.6%. This study provides a new direction to design polymer acceptors and a novel approach to control phase separation morphology of all-PSCs.
关键词： all-polymer solar cells,phase separation morphology,B←N units,amorphous polymer acceptor,power conversion efficiencies
更新于2025-09-11 14:15:04
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Improved charge transfer, mobility and morphology for high performance panchromatic organic photodetectors by adding PC71BM in P3HT:IEICO-4F
摘要： High performance of panchromatic organic photodetectors (OPDs) with a wide spectral response ranged from 300 to 1000 nm were realized through adding [6,6]-phenyl-C71-butyric acid methylester (PC71BM) fullerene as an electron acceptor into the polymer donor of poly (3-hexylthiophene) (P3HT) and the small molecular non-fullerene acceptor of 2, 2′-((2Z,2′Z)-(((4, 4, 9, 9-tetrakis(4-hexylphenyl)-4, 9-dihydro-sindaceno[1, 2-b:5, 6-b′] dithiophene-2, 7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5, 2-diyl))bis-(methanylylidene))bis(5, 6-di?uoro-3-oxo-2, 3-dihydro-1H-indene-2, 1-diylidene))dimalononitrile (IEICO-4F) host system. The fabricated OPD exhibited a high detectivity (D*) of 1.35 × 1012 Jones at 805 nm by adding 10 wt% PC71BM, which is 1.5 folds higher than it from the control system. The improved performance was mainly attributed to the increased light absorption in the short wavelength range and cascade energy level alignment, which is responsible for the e?cient light harvesting and exciton utilization. Furthermore, the active layer morphology was optimized by adjusting the ratio of PC71BM acceptor, which e?ciently enhances charge transport and mobility of the device as well as suppress bimolecular recombination. This work indicates that adding fullerene into non-fullerene system plays a positive e?ect on the device performance of panchromatic OPDs.
关键词： Film morphology,Charge mobility,Non-fullerene and fullerene acceptors,Panchromatic organic photodetector,Charge transfer
更新于2025-09-11 14:15:04
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Near 5% DMSO is the best: A structural investigation of PEDOT: PSS thin films with strong emphasis on surface and interface for hybrid solar cell
摘要： Effect of dimethyl sulfoxide (DMSO) doping on poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) thin films have been optimized for obtaining better hole transport layer in hybrid solar cell. The correlation between morphology and conductivity is established through atomic force microscopy and transmission length method measurements. On the other hand, change in the shape of the building blocks (from spheroidal-like to ellipsoidal-like) in the PEDOT:PSS films with DMSO concentration is apparent from their electron density profiles and topographies, suggesting possible conformational change (from coil-like to rod-like) in film by X-ray reflectivity. Such change is further evident from their compositional profiles, work functions and electronic band structures estimated from X-ray and ultraviolet photoelectron spectroscopies. In fact, complementary information suggest that near 5% DMSO doped PEDOT:PSS film is governed through maximum in-plane extended ellipsoidal-like blocks as well as well organized in out-of-plane ordering which is likely to be the optimum structure for increased the highest electrical conductivity up to 1230 S/cm. Finally, maximum power conversion efficiency of 11 % with open-circuit voltages around 600 mV, a short-circuit current density higher than 30 mA/cm2 and a fill factor of 59.4% is achieved for the 5% DMSO doped PEDOT:PSS/n-Si hybrid solar cell, which is perfectly correlated with their structure.
关键词： Morphology,Conductivity,PEDOT:PSS,DMSO doping,Hybrid solar cell
更新于2025-09-11 14:15:04