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Temperature uniformity enhancement of densely packed high concentrator photovoltaic module using four quadrants microchannel heat sink
摘要： The dense solar radiation received by a high concentration photovoltaic module (HCPVM) causes a high cell temperature. In this module, multiple solar cells were electrically connected in both series and parallel. The higher temperature of the solar cell in the series string limits the generated power for the whole string. Therefore, it is crucial to employ a uniform cooling mechanism for higher electrical performance along with a longer lifespan. The uniform cooling is required to attain safe operating temperature and prevent the hot spot formation. Hence, in the current work, a four-compartment microchannel heat sink is proposed for the thermal management of HCPVM under high solar concentration of 1000 suns (1 sun = 1000 W/m2). A three-dimensional (3D) conjugate heat transfer model with exergy analysis is developed and validated. This model was used to investigate the effect of inlet and outlet orientation of four quadrants microchannel heat sink as a cooling method for HCPVM. Eight different orientations of parallel-flow and counter-flow conditions were investigated and compared in terms of temperature non-uniformity, module power, and exergy performance. The results showed that the inlet and outlet orientation was a key role affecting the module temperature non-uniformity. For the counter-flow operated heat sinks, the HCPVM can be operated under a temperature non-uniformity of 3.1 °C at total inlet module mass flowrate of 350 g/min and solar concentration ratio of 1000 suns. In addition, the attained HCPVM electrical, thermal, and overall exergy efficiency were 37.2%, 8.2%, and 45.4% respectively at the same conditions.
关键词： Densely packed module,Solar concentration ratio,Exergy analysis,Microchannel heat sink,Uniform cooling
更新于2025-09-23 15:21:01
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Effect of Ga introduction during the second stage of a coevaporation process of Cu(In,Ga)Se2 layers at low temperature on polyimide substrates
摘要： A proper control of Ga concentration pro?le is mandatory to achieve high e?ciency Cu(In,Ga)Se2 (CIGS) solar cells. At low temperature, deep gradients, detrimental for carriers' di?usion, are obtained when CIGS is deposited with a standard three-stage process: an optimization of the process is needed. In this study, we show the impact of a modify three-stage process on the depth of the notch by introducing Ga ?ux during the second stage from 0 nm/min to 1.1 nm/min. A higher open circuit voltage compensated by a lower short current density is obtained due to higher band gap energy. The surface and the bulk of the CIGS layer was analyzed at the end of the second stage by coupling di?erent characterization techniques: glow discharge optical emission spectroscopy, Raman and X-ray photoelectrons spectroscopy. The presence of binary compounds as well as a Ga enrichment at the end of the second stage are observed when Ga is introduced during the second stage.
关键词： low temperature,X-ray photoelectron spectroscopy,solar cells,Cu(In,Ga)Se2,three-stage process,glow discharge optical emission spectroscopy,Raman spectroscopy,CIGS,Ga concentration pro?le
更新于2025-09-23 15:21:01
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Influence of precursor concentration and growth time on the surface morphology and crystallinity of α-Ga<sub>2</sub>O<sub>3</sub> thin films fabricated by mist chemical vapor deposition
摘要： Single-crystal thin films of gallium oxide (Ga2O3), an ultra-wide bandgap semiconductor, were fabricated on c-plane sapphire by mist chemical vapor deposition (mist CVD). The grown ?-Ga2O3 thin films had low surface roughness, and we characterized their initial crystal growth phase by using atomic force microscopy and X-ray diffraction. By varying the precursor concentration, we changed the surface roughness and crystallinity of the thin films. The lattice constants of the ?-Ga2O3 thin films almost matched those of the single crystal in the initial growth phase. We also found that these thin films grew hetero-epitaxially. Finally, mist CVD might have a very short incubation time in this system.
关键词： Gallium oxide,Surface morphology,Crystallinity,Precursor concentration,Mist chemical vapor deposition,Epitaxial growth,Wide bandgap semiconductors
更新于2025-09-23 15:21:01
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Prediction of cadmium concentration in brown rice before harvest by hyperspectral remote sensing
摘要： Cadmium (Cd) contaminated rice has become a global food security issue. Hyperspectral remote sensing can do rapid and nondestructive monitoring of environmental stress in plant. To realize the nondestructive detection of Cd in brown rice before harvest, the leaf spectral reflectance of rice exposed to six different levels of Cd stress was measured during the whole life stages. In addition, the dry weight of rice grain and Cd concentrations in brown rice were measured after harvest. The impact of Cd stress on the quantity and the quality of rice grain and on the leaf reflectance of rice was analyzed, and hyperspectral estimation models for predicting the Cd content in brown rice during three growth stages were established. The results showed that rice plants can impact the quality of the brown rice seriously, even if the impact on the quantity was not significant. All the established models had the capability to estimate Cd concentrations in brown rice (R2 > 0.598), and the best performance model, with the R2 value of 0.873, was use first derivative spectrum of booting stage as variable. It was concluded that the hyperspectral of rice leaves provides a new insight to predict Cd concentration in brown rice before harvest.
关键词： Derivative transformation,Brown rice,Booting stage,Before harvest,Hyperspectral,Cd concentration
更新于2025-09-23 15:21:01
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Optical Chirality Sensing with an Auxiliary-free Earth-abundant Cobalt Probe
摘要： Broadly useful chiroptical ee sensing remains challenging and typically involves carefully designed molecular receptors or supramolecular assemblies. Herein, we describe enantioselective sensing of 35 amino acids, amino phosphonic acids, hydroxy acids, amino alcohols and diamines with an auxiliary-free cobalt probe. Chiroptical analysis of the enantiomeric composition and concentration of minute sample amounts is achieved with high accuracy using earth-abundant cobalt salts and hydrogen peroxide as oxidant. Despite the absence of an auxiliary ligand, the cobalt assay is applicable to aromatic and aliphatic compounds and yields strong CD signals at high wavelengths. This method eliminates the general prerequisite for chromophoric metal ligands to generate chiroptical signals via ECCD effects or through analyte-to-ligand chirality induction, and it offers operational simplicity, cost-efficiency, waste reduction and speed.
关键词： ee determination,concentration analysis,Werner complexes,Chirality sensing,chiroptical spectroscopy
更新于2025-09-23 15:21:01
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Primary Determination of Particle Number Concentration with Light Obscuration and Dynamic Imaging Particle Counters
摘要： Accurate number concentrations of particles in liquid media are needed to assess the quality of water, pharmaceuticals, and other liquids, yet there are limited reference materials or calibration services available with clear traceability to the International System of Units. We describe two methods, based on very simple modifications of commercial particle counter instruments, that can provide traceable number concentration measurements. One method used a light obscuration counter. Fitting a model to the data enabled correction for timing and coincidence errors, and gravimetric calibration of the syringe pump gave a traceable determination of measured volume. Other potential biases were diagnosed by analysis of the particle size distribution. The other method used a dynamic imaging particle counter (a flow imaging microscope). The instrument was intentionally configured so that each particle passing through the flow cell was imaged multiple times. Following the particle image acquisition runs, runs with a rinse solution released and counted microspheres adsorbed to tubing or flow-cell walls. Software assembled the redundant particle images into tracks, and the total number of tracks was assigned as the number of particles counted. Both light obscuration and dynamic imaging methods, when applied to polystyrene microspheres of approximately 4 μm diameter, achieved expanded uncertainties (k = 2) of approximately 2 % of number concentration and agreed to within a difference of 1.1 %.
关键词： number density,light obscuration,flow imaging,microspheres,concentration standard,particle concentration,flow microscopy,dynamic imaging,number concentration
更新于2025-09-23 15:19:57
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Decent efficiency improvement of organic photovoltaic cell with low acidic hole transport material by controlling doping concentration
摘要： Presently, poly (3, 4-ethylenedi-oxythiophene): polystyrene sulfonic acid (PEDOT:PSS) is most commonly used hole transport material (HTM) in photovoltaic (PV) cells but its higher acidity, hygroscopicity, high price have motivated people to develop a good substitute. Here, we prepare a series of PSS-doped polyaniline (PANI) with synergic (around 90%) transmittance and work function value (within 5.09-5.16 eV) varying PSS concentrations to check the possible utility as HTM in a poly (3-hexylthiophene): [6, 6]-indene-C60 bisadduct based organic photovoltaic (OPV) cell. Here, it is observed that, because of change in conductivity, the PV performance of those OPV devices is strongly dependent on the doping concentration of the HTM and, at optimized PSS concentration, PANI:PSS has higher conductivity. This facilitates better hole extraction efficiency into the PV device and results in higher short circuit current density (JSC). Therefore, the PANI:PSS-based OPV device with optimized PSS concentration exhibits same level of power conversion efficiency (PCE: 4.5±0.2 %) as a PEDOT:PSS based OPV device. Thus, a lower acidic (pH = 2.2) p-type semiconductor PANI:PSS (weight ratio = 1:1 and) can be a good alternative to highly acidic (pH = 1.7) PEDOT:PSS ( weight ratio = 1:6, Clevious Al 4083) for using as HTM in an OPV device.
关键词： Hole transport layer,Organic photovoltaic cell,Doping concentration,Poly (4-styrenesulfonic acid) doped poly (3, 4-ethylenedi-oxythiophene),Poly (4-styrenesulfonic acid) doped polyaniline
更新于2025-09-23 15:19:57
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Enhancement in the efficiency of Sb2Se3 solar cells by adding low lattice mismatch CuSbSe2 hole transport layer
摘要： As an excellent light absorbing material, antimony selenide (Sb2Se3) has attracted researchers to explore its application in solar cells. At present, the e?ciency of Sb2Se3 solar cells is still too low because of the low carrier concentration and high back surface recombination. In this study, we prepared an additional CuSbSe2 ?lm as hole transport layer by co-sputtering Sb2Se3 and Cu targets. It reduced the surface roughness of the absorption layer and the back surface recombination, which was bene?cial to the collection of carriers. Due to the higher carrier concentration of CuSbSe2 ?lm and proper di?usion of Cu, the carrier concentration of the absorption layer is greatly improved, thereby e?ectively increasing the Voc of the Sb2Se3 thin ?lm solar cells. Finally, we obtained a 5.87% e?ciency for the FTO/CdS/Sb2Se3/CuSbSe2/Au solar cell, which is more than 25% higher than the basic e?ciency.
关键词： Carrier concentration,CuSbSe2,Co-sputtering,Sb2Se3,Lattice mismatch
更新于2025-09-23 15:19:57
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Raman and infrared spectroscopic quantification of the carbonate concentration in K2CO3 aqueous solutions with water as an internal standard
摘要： Carbonate-bearing fluids widely exist in different geological settings, and play important roles in transporting some elements such as the rare earth elements. They may be trapped as large or small fluid inclusions (with the size down to <1 μm sometimes), and record critical physical-chemical signals for the formations of their host minerals. Spectroscopic methods like Raman spectroscopy and infrared spectroscopy have been proposed as effective methods to quantify the carbonate concentrations of these fluid inclusions. Although they have some great technical advantages over the conventional microthermometry method, there are still some technical difficulties to overcome before they can be routinely used to solve relevant geological problems. The typical limitations include their interlaboratory difference and poor performance on micro fluid inclusions. This study prepared standard ion-distilled water and K2CO3 aqueous solutions at different molarities (from 0.5 to 5.5 mol/L), measured densities, collected Raman and infrared spectra, and explored correlations between the K2CO3 molarity and the spectroscopic features at ambient P-T conditions. The result confirms that the Raman O-H stretching mode can be used as an internal standard to determine the carbonate concentrations despite some significant differences among the correlations, established in different laboratories, between the relative Raman intensity of the C-O symmetric stretching mode and that of the O-H stretching mode. It further reveals that the interlaboratory difference can be readily removed by performing one high-quality calibration experiment, provided that later quantifying analyses are conducted using the same Raman spectrometer with the same analytical conditions. Our infrared absorption data were collected from thin fluid films (thickness less than ~2 μm) formed by pressing the prepared solutions in a Microcompression Cell with two diamond-II plates. The data show that both the O-H stretching mode and the O-H bending mode can be used as internal standards to determine the carbonate concentrations. Since the IR signals of the C-O antisymmetric stretching vibration of the CO3 2- ion, and the O-H stretching and bending vibrations from our thin films are very strong, their relative IR absorbance intensity, if well calibrated, can be used to investigate the micron-sized carbonate-bearing aqueous fluid inclusions. This study establishes the first calibration of this kind, which may have some applications. Additionally, our spectroscopic data suggest that as the K2CO3 concentration increases the aqueous solution forms more large water molecule clusters via more intense hydrogen-bonding. This process may significantly alter the physical and chemical behavior of the fluids.
关键词： Relative IR absorbance,K2CO3 concentration,Relative Raman intensity,Carbonate aqueous solution,Micro fluid inclusion
更新于2025-09-23 15:19:57
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Gas distribution mapping for indoor environments based on laser absorption spectroscopy: Development of an improved tomographic algorithm
摘要： Gas distribution mapping (GDM) is an important technology for the study of indoor environment, which can be used to evaluate the efficiency of environmental control system and identify pollutant sources. Most recent studies have implemented GDM through contact sensors or a sensor network, which is difficult to calibrate all the sensors and cover the whole space. In this study, we introduced the non-contact tunable diode laser absorption spectroscopy (TDLAS) technology for GDM in the indoor environment. An improved tomographic algorithm, namely Least Square with Tikhonov Regularization (LSTR), was proposed and compared with two available tomographic algorithms using four validated computational fluid dynamics (CFD) simulations. We also analyzed the effects of the laser emitter placements and optical path densities on the concentration field reconstruction quantitatively. The results showed that the LSTR method could reduce the average relative root mean square error (RRMSE) of tomography by 52%, and the laser emitter at the long edge middle (LEM) can achieve better tomographic performance. The degree of the concentration dispersion from the source would mainly impact the tomographic results: when the sector dispersion (SD) value of concentration distribution was about 2.3 times larger, the average RRMSE value would be decreased by about 40%. The intersection matrix with a higher path density achieved a more accurately reconstructed map due to its lower condition number. In addition, the optical path density was suggested to twice the number of grid cells considering the trade-off between scanning time and accuracy.
关键词： Non-contact sensing,Tunable diode laser absorption spectroscopy (TDLAS),Concentration measurement,Indoor air,Air pollution
更新于2025-09-23 15:19:57