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Nonconstant Enthalpy of thermosetting solid-solid Phase Change Materials Controlled by Light
摘要： Phase change materials (PCMs) based on the principle of latent heat thermal energy storage have been highly concerned by researchers and widely developed in various fields. However, for traditional PCMs, especially thermosetting solid-solid change materials (SSPCMs) which usually consist of crosslinking structure, the phase change enthalpy was fixed once the materials were constructed. To turn the constant enthalpy into adjustable one, we incorporated the light-sensitive methyl red (MR) groups into polyurethane-based SSPCMs. The MR-containing SSPCMs exhibit amplified enthalpy and increased melting temperature (Tm) after activated by UV light compared with the inactivated ones. UV treatment can promote the crystallization of the soft segment in polyurethane due to the light-induced isomerization of MR groups and visible light causes reverse effect of the activated samples that the enthalpy, Tm and crystallization get back to the original degree, which indicates the nonconstant enthalpy. A separation theory was proposed to explain the increased enthalpy and Tm caused by the cis configuration of MR groups.
关键词： nonconstant enthalpy,methyl red,separation theory,isomerization,irradiation
更新于2025-09-23 15:19:57
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Enhanced Performances of p-Si/n-ZnO Self-powered Photodetector by Interface State Modification and Pyro-phototronic Effect
摘要： ZnO based self-powered photodetector (PD) has great application potential in distributing sensor networks and internet of things. However, a large number of surface or interface states within ZnO limit its performance improvement. Here, the surface and interface states of ZnO is greatly eliminated by ultraviolet irradiation as an interfacial modification engineering. Reduction of interface states reduces ohmic resistance, also enhances the tuning role of pyro-phototronic effect. And the transient response currents of the self-powered PD are thus significantly improved with a maximal enhancement factor of more than 5900% for the 325-785 nm broadband stimulating beams. The corresponding response time is decreased to few milliseconds or sub-milliseconds. The results indicate that surface-state reduction of ZnO can effectively enhance the modifying role of pyro-phototronic effect and greatly improve the response performances of the self-powered broadband PDs with great application demands in Internet of things, broad spectral detecting and imaging, and smart optoelectronic devices.
关键词： Self-powered,ultraviolet irradiation,interface states,pyro-phototronic effect,broadband photodetectors
更新于2025-09-23 15:19:57
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Elucidating the mechanism of potential induced degradation delay effect by ultraviolet light irradiation for p-type crystalline silicon solar cells
摘要： A mechanism of potential induced degradation (PID) delay effect by ultraviolet (UV) light irradiation during PID test for p-type crystalline silicon (c-Si) solar cells was proposed in this work. The degradation rate of the solar cell performances is slowed down by the UV light irradiation in the 300–390 nm wavelength range during PID test. The conductivity increase of the silicon nitride (SiNx) anti-reflection coating (ARC) layer on the solar cell surface under UV light irradiation during PID tests, which relates to the mechanism preventing the penetration of sodium ions into the active cell layer, induces the PID delay effect for the p-type c-Si solar cells. The PID delay effect was also analyzed by a microwave photo-conductance decay (μ-PCD) technique in this work. The reduction behavior of the components in the μ-PCD signal curves including rapid (τ1) and slow (τ2) decay time constants and the effective lifetime (τeff) presents a good correlation with the performance degradation behavior of the solar cells over PID test duration. Moreover, the reduction rate of these components is also slowed down under the UV light irradiation in the 300–390 nm wavelength range during PID tests. Notably, their reduction behavior was compatible with the mechanism of the conductivity increase of the SiNx ARC layer under UV light irradiation.
关键词： Potential induced degradation (PID),Silicon solar cells,UV irradiation,Silicon nitride (SiNx),Microwave photo-conductance decay
更新于2025-09-23 15:19:57
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Method for Measuring the Absolute Spectral Response of Infrared Photodetector Arrays
摘要： Physical and technical aspects of the implementation of an alternative method for measuring the absolute spectral response of infrared photodetector arrays (IR PDA) (current sensitivity spectrum, voltage sensitivity, and quantum efficiency) without the use of spectral instruments are considered. The method is based on multiple measurements of the output signal of all IR array’s photosensitive elements (PSEs) generated by modulated black-body radiation at different temperatures of the black body (BB). The signal is measured against the sum of constant signals from the background radiation, the detector input optical window, the BB radiation modulator, the PSE dark current, and the constant signal of the LSI multiplexer. A system of Fredholm integral equations of the first kind is constructed based on the measured PSE signals. Its left side includes measured BB signals and, the right side, analytical expressions describing these signals. The solution of the system are the absolute values of the above-mentioned spectral components of all PSEs of PDAs. The block diagram of the measurement setup is considered, functional features of its operation are analyzed, and requirements for its blocks are substantiated. Additional advantages of the new method in comparison with the existing methods are presented.
关键词： useful and stray irradiation,current and voltage sensitivity spectra,PSE red boundary histogram,PSE red boundary distribution on IR array area,BB radiation modulation,IR PDA output signal,quantum efficiency spectrum
更新于2025-09-23 15:19:57
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Structural Transformations of a Carbon Nanomaterial under High-Energy Laser Irradiation
摘要： Pulsed-laser irradiation of a globular turbostratic carbon material under diverse conditions was carried. A TEM examination revealed formation of nanostructured particles (nanocapsules) under exposure to 1064 nm pulsed radiation at the power density of 108 W/cm2, whose increase to 1011 W/cm2 led to formation of structures with a higher degree of ordering. Pulsed irradiation of the initial globules at 532 nm wavelength allowed reducing the interplanar spacings of the graphene layers in the resultant nanocapsules from 0.410 to 0.346 nm. The dependence of the maximum heating temperature of the nanoparticles on the power density in the laser spot was analyzed. The in? uence of the heating temperature of the carbon nanomaterial on its structure and morphology was assessed.
关键词： carbon nanomaterials,nanocapsules,power density,transmission electron microscopy,laser irradiation
更新于2025-09-23 15:19:57
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Improving Radiation Resistance of GaInP/GaInAs/Ge Triple-Junction Solar Cells Using GaInP Back-Surface Field in the Middle Subcell
摘要： This paper studies the radiation resistance for GaInP/GaInAs/Ge triple-junction space solar cells with a GaInP back-surface ?eld (BSF) in the GaInAs middle subcell compared with those with an AlGaAs BSF. The results show that the initial electrical performance is almost the same for both of them. However, the radiation resistance of the GaInP BSF cell was improved. After irradiation by 1 MeV electron beam with a cumulative dose of 1015 e/cm2, the Jsc declined by 4.73% and 6.61% for the GaInP BSF cell and the AlGaAs BSF cell, respectively; the e?ciency degradation was 13.64% and 14.61% for the GaInP BSF cell and the AlGaAs BSF cell, respectively, leading to a reduced degradation level of 6%. The mechanism for GaInP BSF to improve the radiation resistance of GaInP/GaInAs/Ge triple-junction solar cells is also discussed in this work. Similar results were obtained when irradiation cumulative doses varied from 1 × 1014 e/cm2 to 1 × 1016 e/cm2.
关键词： back-surface ?eld,electron beam irradiation,GaInP/GaInAs/Ge triple-junction space solar cell,radiation resistance
更新于2025-09-23 15:19:57
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Reversible and tunable photochemical switch based on plasmonic structure
摘要： For the first time, pyranine (8-hydroxypyrene-1,3,6-trisulfonate, HPTS) is studied for realizing active plasmonic control, which is attracted considerable attention owing to its unique photophysical and photochemical properties. We have used this photoacid (HPTS) as an active surrounding medium that can be optically controlled and used for modulating plasmon resonances. In this paper, the fabrication of 2D-plasmonic grating coated by thin film of HPTS exposed to UV irradiation is reported. By switching the UV light on and off, the HPTS thin film maintains an excited-state proton transfer (ESPT) process followed by green fluorescence resulting in a plasmonic redshift caused by the variation of the refractive index. Furthermore, this photochemical active medium has also played another important role in plasmonic sensing, in which the emission-based response of HPTS thin film in 2D-plasmonic grating to water vapor upon photoexcitation is demonstrated, for both s and p polarizations. This tunable, flexible and reversible light-driven system will enhance the development of active plasmonic structures and will have a great influence on many fields such as, biochemical optical sensors and all-optical plasmonic circuits.
关键词： photochemical switch,UV irradiation,plasmonic sensing,plasmonic structure,HPTS
更新于2025-09-23 15:19:57
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Sculpting Artificial Edges in Monolayer MoS <sub/>2</sub> for Controlled Formation of Surface-Enhanced Raman Hotspots
摘要： Hotspot engineering has the potential to transform the field of Surface-Enhanced Raman Spectroscopy (SERS) by enabling ultra-sensitive and reproducible detection of analytes. However, the ability to controllably generate SERS hotspots, with desired location and geometry, over large-area substrates, has remained elusive. In this study, we sculpt artificial edges in monolayer Molybdenum Disulfide (MoS2) by low-power focused laser-cutting. We find that when gold nanoparticles (AuNPs) are deposited on MoS2 by drop-casting, the AuNPs tend to accumulate predominantly along the artificial edges. First-principles density functional theory (DFT) calculations indicate strong binding of AuNPs with the artificial edges due to dangling bonds that are ubiquitous on the un-passivated (laser-cut) edges. The dense accumulation of AuNPs along the artificial edges intensifies plasmonic effects in these regions creating hot spots exclusively along the artificial edges. DFT further indicates that adsorption of AuNPs along the artificial edges prompts a transition from semiconducting to metallic behavior, which can further intensify the plasmonic effect along the artificial edges. These effects are observed exclusively for the sculpted (i.e., cut) edges and not observed for the MoS2 surface (away from the cut edges) or along the natural (passivated) edges of the MoS2 sheet. To demonstrate the practical utility of this concept, we use our substrate to detect Rhodamine B (RhB) with large SERS enhancement (~104) at the hotspots for RhB concentrations as low as ~10-10 M. The single-step laser etching process reported here can be used to controllably generate arrays of SERS hotspots. As such, this concept offers several advantages over previously reported SERS substrates that rely on electro-chemical deposition, e-beam lithography, nanoimprinting or photolithography. While we have focused our study on MoS2, this concept could in principle, be extended to a variety of 2D material platforms.
关键词： focused laser irradiation,MoS2,localized hotspots,artificial edges,SERS
更新于2025-09-23 15:19:57
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Changes in the Photoluminescence of Monolayer and Bilayer Molybdenum Disulfide during Laser Irradiation
摘要： Various postsynthesis processes for transition metal dichalcogenides have been attempted to control the layer number and defect concentration, on which electrical and optical properties strongly depend. In this work, we monitored changes in the photoluminescence (PL) of molybdenum disulfide (MoS2) until laser irradiation generated defects on the sample flake and completely etched it away. Higher laser power was required to etch bilayer MoS2 compared to monolayer MoS2. When the laser power was 270 μW with a full width at half-maximum of 1.8 μm on bilayer MoS2, the change in PL intensity over time showed a double maximum during laser irradiation due to a layer-by-layer etching of the flake. When the laser power was increased to 405 μW, however, both layers of bilayer MoS2 were etched all at once, which resulted in a single maximum in the change of PL intensity over time, as in the case of monolayer MoS2. The dependence of the etching pattern for bilayer MoS2 on laser power was also reflected in position changes of both exciton and trion PL peaks. The subtle changes in the PL spectra of MoS2 as a result of laser irradiation found here are discussed in terms of PL quantum efficiency, conversion between trions and excitons, mean interatomic spacing, and the screening of Coulomb interaction.
关键词： photoluminescence,defects,etching,laser irradiation,molybdenum disulfide
更新于2025-09-23 15:19:57
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The environment coefficients effect on I-V and P-V characteristics curves of photovoltaic cell using Matlab/Simulink
摘要： Many parameters and environments conditions will affect the behavior of the photovoltaic cell. This paper investigates, theoretically the variation of each temperature and irradiation effects on the output of the photovoltaic cell characteristics. Modeling of the photovoltaic cell scheme essentially requires taking weather data (temperature and irradiance) as input variables. The photovoltaic outputs are the current, voltage and power. Though, conclude the characteristics I-V or P-V desires of these important variables. Any variation in the entries directly shows variations in outputs. The characteristic curves are obtained with the use practical readings and measurements are illustrated directly from the solar power plant in the Technical Engineering College of Mosul. The complete modeling is then computer-generated using MATLAB/Simulink software owing to its common use and its helpfulness.
关键词： Solar Cell,PV Cell,Single Diode,PV Temperature,PV Irradiation,I-V and P-V Characteristics
更新于2025-09-23 15:19:57