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Effect of liquid environment on single-pulse generation of laser induced periodic surface structures and nanoparticles
摘要： The effect of a liquid environment on the fundamental mechanisms of surface nanostructuring and generation of nanoparticles by single pulse laser ablation is investigated in a closely integrated computational and experimental study. A large-scale molecular dynamics simulation of spatially-modulated ablation of Cr in water reveals a complex picture of dynamic interaction between the ablation plume and water, which involves rapid deceleration of the ablation plume by water environment, formation and prompt disintegration of a hot metal layer at the interface between the ablation plume and water, lateral redistribution and redeposition of a major fraction of the ablation plume, and eventual formation of smooth frozen surface features. A good agreement between the shapes of the surface features predicted in the simulation and the ones generated in single pulse laser ablation experiments performed for Cr in water supports the mechanistic insights revealed in the simulations. The results of this study suggest that the presence of liquid environment can eliminate the sharp features of surface morphology, reduce the amount of material removed from the target by more than an order of magnitude, and narrow down the nanoparticle size distribution as compared to laser ablation in vacuum. Moreover, the computational predictions of the effective incorporation of molecules constituting the liquid environment into the surface region of the irradiated target and the generation of high vacancy concentrations exceeding the equilibrium levels by more than an order of magnitude suggest a potential for hyperdoping of laser-generated surfaces by solutes present in the liquid environment.
关键词： Laser-Induced Periodic Surface Structures (LIPSS),Generation of Nanoparticles,Crystal Defects,Surface Morphology,Hyperdoping,Molecular Dynamics Simulations,Pulsed Laser Ablation in Liquids
更新于2025-09-19 17:13:59
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Improvement of ablation capacity of sapphire by gold film-assisted femtosecond laser processing
摘要： Sapphire is widely used in civilian and military equipment owing to its superior optical and mechanical properties. Femtosecond laser has been demonstrated to be an effective tool to process sapphire material. However, the direct processing of sapphire by femtosecond laser still meets some challenges, such as poor ablation morphology and low laser energy absorption. In this work, femtosecond laser processing of sapphire coated with a 12-nm-thick gold film (Au-coated sapphire) has been investigated. The experimental results have revealed that the ablation morphology of Au-coated sapphire has been improved, featuring fewer molten materials and thermal cracks, as well as regular crater shape and uniform periodic surface structures. It has also been found that, under 100 shots condition, the threshold fluence of Au-coated sapphire is reduced by about 56% compared to that of uncoated one. Meanwhile, the incubation effect of Au-coated sapphire is stronger than that of uncoated one. We also illustrate that the material removal rate of Au-coated sapphire is increased up to about two times higher than that of uncoated one. In order to reveal the effective mechanism of the gold film in the laser processing of sapphire, the energy transfer process among incident photons, free electrons and sapphire lattice phonons was studied. Our study provides a guidance for improving the laser ablation capacity of sapphire.
关键词： Gold film,Sapphire,Material removal rate,Ablation morphology,Femtosecond laser processing
更新于2025-09-19 17:13:59
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Effects of Cr2O3 active agent on the weld process dynamic behavior and joint comprehensive properties of fiber laser welded stainless steel thick plate
摘要： In this study, the dynamic behaviors of metal vapor, plasma, keyhole, and weld pool during activating laser welding of stainless steel thick plates are monitored in real time by employing a novel "sandwich" method in combination with a high-speed camera system. Meanwhile, the welding quality of specimens is inspected and analyzed from the aspects like joint weld formation, mechanical properties, microstructure, and element distribution. The effects of Cr2O3 active agent on the welding stability and quality of specimens are explored. According to the results, adequate coating of active agent on the specimen surface can weaken and suppress the generation and drastic changes of metal vapor and plasma inside and outside the keyhole, increase the keyhole depth, improve the keyhole shape, weaken the oscillation amplitude of weld pool, and prolong the change cycles of keyhole and weld pool. Consequently, the stability of welding process is enhanced, the generation of porosity and splash defects is inhibited preferably, the quality of weld formation is improved, the weld penetration is increased, the grain structure in weld zone is refined, the width of heat affected zone is narrowed, and the joint strength and toughness are enhanced, without showing apparent change of the relative element contents in the welded joint. In conclusion, coating of Cr2O3 active agent on the specimen surface is effective in improving the welding properties of laser welded stainless steel plates.
关键词： Welding quality,Fiber laser welding,Plasma morphology,Cr2O3 active agent,Weld pool behavior
更新于2025-09-19 17:13:59
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π–π Stacking Distance and Phase Separation Controlled Efficiency in Stable All-Polymer Solar Cells
摘要： The morphology of the active layer plays a crucial role in determining device performance and stability for organic solar cells. All-polymer solar cells (All-PSCs), showing robust and stable morphologies, have been proven to give better thermal stability than their fullerene counterparts. However, outstanding thermal stability is not always the case for polymer blends, and the limiting factors responsible for the poor thermal stability in some All-PSCs, and how to obtain higher efficiency without losing stability, still remain unclear. By studying the morphology of poly [2,3-bis (3-octyloxyphenyl) quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl](TQ1)/poly[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]] (PCE10)/PNDI-T10 blend systems, we found that the rearranged molecular packing structure and phase separation were mainly responsible for the poor thermal stability in devices containing PCE10. The TQ1/PNDI-T10 devices exhibited an improved PCE with a decreased π–π stacking distance after thermal annealing; PCE10/PNDI-T10 devices showed a better pristine PCE, however, thermal annealing induced the increased π–π stacking distance and thus inferior hole conductivity, leading to a decreased PCE. Thus, a maximum PCE could be achieved in a TQ1/PCE10/PNDI-T10 (1/1/1) ternary system after thermal annealing resulting from their favorable molecular interaction and the trade-off of molecular packing structure variations between TQ1 and PCE10. This indicates that a route to efficient and thermal stable All-PSCs can be achieved in a ternary blend by using material with excellent pristine efficiency, combined with another material showing improved efficiency under thermal annealing.
关键词： morphology,device stability,crystallinity,all-polymer solar cells,thermal annealing,molecular packing structure
更新于2025-09-19 17:13:59
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Enhancement of efficiency of single walled carbon nanotubes-n-type silicon solar cells using molybdenum disulfide
摘要： This study focuses on the improvement of ef?ciency of single walled carbon nanotubes and n-type silicon (SWCNTs-n-type-Si) based solar cells using molybdenum disul?de (MoS2). Initially, different hybrid MoS2/SWCNTs-n-type-Si ?lms were fabricated and optimized the best performing cell. The ?lms were tested through scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy to check their surface morphology, topography, and elemental characteristics, respectively. The long cylinder shape for SWCNTs and crystal sheet for MoS2 were observed, where the SWCNTs were distributed randomly among the MoS2 ?akes. Raman spectra showed the characteristics peaks of SWCNTs, Si, and MoS2. The addition of MoS2 in optimized ?lm has improved the ef?ciency of SWCNTs-n-type-Si solar cells approximately 49%.
关键词： Energy diagram,MoS2,Solar cells,Silicon,Morphology,SWCNTs
更新于2025-09-19 17:13:59
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Understanding the Morphology of High-performance Solar Cells Based on a Low Cost Polymer Donor
摘要： A low cost and high performance bulk heterojunction (BHJ) solar cell comprising an emerging polymer donor, poly[(thiophene)-alt-(6,7-difluoro-2-(2-hexyldecyloxy)quinoxaline)] (PTQ10), shows an efficiency of 12.7%. To improve performance of the solar cells, a better understanding of the structure-property relationships of the PTQ10-based devices is crucial. Here, we fabricate PTQ10/nonfullerene and fullerene BHJ devices, including PTQ10/IDIC, PTQ10/ITIC, and PTQ10/PC71BM, processed with or without thermal annealing and additive, provide detailed descriptions of the relationships between the morphology and performance. PTQ10 is found to be highly miscible with nonfullerene IDIC and ITIC acceptors, and poorly miscible with fullerene PC71BM acceptors. Thermal annealing promotes the crystallization of PTQ10 and phase separation of all PTQ10/IDIC, PTQ10/ITIC, and PTQ10/PC71BM devices, leading to an increased power conversion efficiencies (PCE) of the PTQ10/IDIC and PTQ10/ITIC devices but a decreased PCE of PTQ10/PC71BM devices with 1,8-di-iodooctane (DIO) additive. Without thermal annealing, DIO greatly improves the morphology of PTQ10/PC71BM, leading to a higher PCE. The results show that the degree of phase separation and ordering in the PTQ10-based devices significantly influence device performance. The morphology-property correlations demonstrated will assist in the rational design of this low cost polymer donor based solar cells to achieve even higher performance.
关键词： morphology,phase separation,polymer solar cells,miscibility,crystallization
更新于2025-09-19 17:13:59
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Fabrication of pyramid-BiVO4/CdSe composite with controlled surface oxygen vacancies boosting efficient carriersa?? separation for photocathodic protection
摘要： In order to solve the bottleneck problem of weak efficiency of carriers’ separation and transfer in BiVO4 photocatalyst, a novel pyramid-BiVO4 with sufficient oxygen vacancies was successfully synthesized via a low-temperature solvothermal method. By adjusting solution pH and adding SDBS surfactant, the prepared samples could have a variety of controllable morphologies and exposed {001} facets, which were determined by SEM, XRD, and BET methods. XPS O1s peak and ESR signals indicated that pyramid-BiVO4 exhibited higher oxygen vacancies concentration than others. Besides, CdSe quantum dots (QDs) were introduced to construct BiVO4/CdSe heterojunctions composite based photoanode to further promote solar harvesting and carrier separation. The photoelectrochemical experimental results showed that 304 stainless steel (304SS) coupled with 8V-BC photoanode showed an enhanced photocurrent density (608 μA?cm-2) and maximum potential drop (708 mV), which were equivalent to 5.06 times and 2.10 times that of the original BiVO4, respectively. Mechanism study illustrated that the ultra-high performance of the 8V-BC photoanode was attributed to the synergistic effect of enriched oxygen vacancies, exposed {001} facets, enlarged visible light absorption and larger specific surface area.
关键词： oxygen vacancies,photocathodic protection,CdSe,BiVO4,morphology controlled
更新于2025-09-19 17:13:59
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Elucidating Roles of Polymer Donor Aggregation in All-Polymer and Non-Fullerene Small-Moleculea??Polymer Solar Cells
摘要： The aggregation behavior of polymers plays a crucial role in determining the optical, electrical, and morphological properties of donor-acceptor blends in both all-polymer solar cells (all-PSCs) and non-fullerene small molecule acceptor-polymer solar cells (NFSMA-PSCs). However, direct comparison of the impacts on two different systems has not been reported, although it is important to design universal polymer donors (PDs). Herein, three PDs with different side chains (P-EH, P-SEH and P-Si) are designed to study the PD aggregation effects on the blend morphology and device performance of both all-PSCs and NFSMA-PSCs. It is observed that the aggregation property of PDs is a critical factor in determining the optimal blend morphologies and ultimately the device performances in both the PSC systems. Furthermore, PD aggregation effects on device performance is significantly more impactful in all-PSCs than in NFSMA-PSCs. The P-Si PD exhibiting the strongest aggregation behavior in a processing solvent produces the most severe phase separation in the blend with a polymer acceptor, resulting in the lowest power conversion efficiency (PCE) of all-PSCs. In contrast, when P-Si is used in an NFSMA-PSC, a well-mixed blend morphology is observed, which results in the highest PCE of over 12%. These different roles dependent on PD aggregation mainly originate from the difference in molecular size of polymer acceptor and small molecule acceptor, which influences the entropic contribution to the formation of blend morphology. Our work provides a comprehensive understanding on the PD aggregation-blend morphology relationship in different all-PSC and NFSMA-PSC systems, which serves as an important guideline for the design of universal PDs for both all-PSCs and NFSMA-PSCs.
关键词： polymer solar cells,all-polymer solar cells,non-fullerene small molecule acceptor-polymer solar cells,polymer donor aggregation,blend morphology,power conversion efficiency
更新于2025-09-19 17:13:59
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Ultrafast Hole Transfer and Carrier Transport Controlled by Nanoscale-Phase Morphology in Nonfullerene Organic Solar Cells
摘要： Nonfullerene acceptors (NFAs) have attracted great attention in high-efficiency organic solar cells (OSCs). While the effect of molecular properties including structures and energetics on charge transfer have been extensively investigated, the effect of macroscopic phase properties is yet to be revealed. Here we have performed a correlation study of the nanoscale phase morphology on photoexcited hole transfer (HT) process and photovoltaic performance, by combing ultrafast spectroscopy with high temporal resolution and photo-induced force microscopy (PiFM) with high spatial and chemical resolution. In PM6/IT-4F, we observe a biphasic HT behavior with a minor ultrafast (< 100 fs) interfacial process and a major diffusion mediated HT process till ~ 100 ps, which depends on phase segregation strongly. Because of the interplay between charge transfer and transport, a compromised domain size of 20 ~ 30 nm for NFAs shows best performance. This study highlights the critical role of phase morphology in high-efficiency OSCs.
关键词： photo-induced force microscopy,phase morphology,ultrafast spectroscopy,organic solar cells,hole transfer,Nonfullerene acceptors
更新于2025-09-19 17:13:59
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Electronic Coordination Effect of the Regulator on Perovskite Crystal Growth and Its High-Performance Solar Cells
摘要： The rapid growth of perovskite crystal leads to excessive grain boundaries and surface defects, which has a negative effect on the performance of solar cells (PSCs). Passivating defects by controlling the crystal growth rate becomes a crucial research hotspot for preparing high crystallinity perovskite films. In this work, phenylacetonitrile (PA) and 2-naphthylacetonitrile (2-NA) served as crystal growth regulators are introduced into the perovskite precursor. The coordination effect of lone-pair electrons (n-electrons) and π-electrons in regulator molecule with Pb2+ on the nucleation and growth of FA0.80MA0.15Cs0.05Pb(I0.85Br0.15)3 perovskite crystal, along with passivation of surface defects and grain boundaries are systematically investigated. The n-electrons of N atom form a coordination bond with Pb2+, and π-electrons in aromatic ring generate a cation-π interaction with Pb2+. This combined effect efficiently delays the crystallization rate of perovskite crystal, and then promotes the grain growth and reduces the grain boundaries, which is favorable for the dissociation of more excitons to carriers. The PA-optimized PSCs show an increasement of PCE from 18.01% to 21.09%, with an unencapsulated device retaining 91.2% of its initial efficiency for 60 days in 40 ± 5% relative humidity under dark condition.
关键词： perovskite solar cells,coordination effect,crystal growth regulator,passivation defects,morphology,cation-π
更新于2025-09-19 17:13:59