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Cone-straight nozzle has been widely used in well bore cleaning, assisting drilling in petroleum industries due to its good clustering properties. The structure including cone angle and throat length has also been studied by scholars and been optimized. However, the internal flow properties have not been investigated clearly especially the boundary layer flow. In this paper LES model is used to capture the small-scale flow state near the nozzle wall. The RNG k-epsilon model is used to validate the accuracy of the LES simulation, the simulation data shows a good agreement. Three different inlet velocities are considered in simulations. The velocity distribution, shear stress, boundary layer thickness, skin friction coefficient and Reynolds stress are analyzed, the boundary layer separation and transition are discussed. The state of flow inside nozzle is laminar with inlet velocity of 1 m/s and gradually transferred into turbulent with the increasing inlet velocity. The most severe turbulence is at the entrance of the throat section, the vortex structure appears at the entrance of converging section and dose not survive, the vortex structure appears in sequence along the throat section wall when the inlet velocity is set to 5 m/s and 10 m/s the flow properties along the conical nozzle are revealed clearly, the main flow resistance is mainly produced in throat section. All these works aim to provide theoretical support for the further processing optimization of the nozzle structure and reduce the flow resistance of nozzle.

Retracted Article: Experimental study on electro-mechanical response characteristics of PZT5H piezoelectric ceramics under impact loadingWe, the Editors and Publisher of Advances in Applied Ceramic...

In this paper, we report a p-GaN/n-ZnO nanoplate/CsPbBr3 quantum dots (QDs) heterojunction light-emitting diode (LED) for dual-wavelength emission. ZnO nanoplates were prepared by vapor phase transport on the GaN thin film to form the p-GaN/n-ZnO nanoplate heterojunction. Afterwards, green CsPbBr3 QDs (band gap of 2.25 eV) were deposited on ZnO nanoplates to realize green light emission. The structure and photoluminescence of the ZnO nanoplates and CsPbBr3 QDs were characterized. The as-prepared LED device with turn-on voltage of ∼ 2.7 V displays a typical rectification behavior. The electroluminescence spectra with narrow emission peaks reveal the device presents commendable dual-wavelength electroluminescence performance at ∼ 385 nm and ∼ 512 nm and the electroluminescence intensity saturates at about 65 mA/cm2. Moreover, the detailed electroluminescence mechanism including emission originate of n-ZnO/p-GaN heterojunction was discussed based on the band diagram. Thus, our work indicates compelling potential for the practical application of perovskite LEDs.

Effective Mn2+ doping in a CsPbCl3 lattice utilizing manganese acetate and trimethylchlorosilane is achieved via a one-pot hot-injection synthesis method. This strongly contrasts to the previous case, where only the MnCl2 precursor was suitable for Mn2+ doping by considering the matching of bond dissociation energies between Mn-Cl and Pb-Cl. The Mn doping concentration and luminescence quantum yield are highly dependent on trimethylchlorosilane content. A new doping mechanism is proposed, where the incorporation of Mn2+ into CsPbCl3 is achieved via directly inserting [MnCl6]4- octahedra into the perovskite structure during the nucleation/growth processes instead of Mn-to-Pb cation exchange. Accordingly, increasing Cl- content in the reaction solution indeed promotes the doping of other divalent transition metal ions such as Ni2+, Cu2+ and Zn2+ in CsPbCl3 and improve the quantum yield of CsPbCl3 nanocrystals up to ∼20% compared to the undoped counterparts (∼1%).

In the last few years, all-inorganic cesium lead halide (CsPbX3) quantum dots have shown unprecedented radical progress for practical applications in the optoelectronic field, but they quickly decompose when exposed to air. The in situ growth of the CsPbX3 particles inside amorphous glass can significantly improve their stability. Unfortunately, it is formidably difficult to precipitate whole-family CsPbX3 from a glass matrix and their photoluminescence quantum yields require further improvement. Herein, fluoride additives were introduced into oxyhalide borosilicate glasses to break the tight glass network, which promoted the nucleation/growth of CsPbX3 (X = Cl, Cl/Br, Br, Br/I and I) inside the glass. Importantly, the quantum efficiencies of glass-stabilized CsPbBr3, CsPb(Br/I)3 and CsPbI3 reached 80%, 60% and 50%, respectively, which are the highest efficiencies reported so far. Benefiting from the effective protection of robust glass, CsPbX3 quantum dots exhibited superior water resistance with more than 90% luminescence remaining after immersing them in water for 30 days, and halogen anion exchange among different CsPbX3 materials was completely inhibited. Two prototype light-emitting diodes were constructed by coupling green/red and green/orange/red quantum dots with InGaN blue chips, yielding bright white light with optimal luminous efficiency of 93 lm W−1, tunable color temperature of 2000–5800 K and high color rendering index of 90.

Currently, it is of great challenge to achieve cation exchange in CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) on account of rigid Pb2+ octahedral coordination protected by six halogen anions (PbX64–). Herein, we demonstrate that dynamic halogen exchange can effectively open up PbX64– octahedrons and enable fast Mn-to-Pb cation exchange at room temperature in a few seconds. Importantly, Cl concentration rather than Mn one is demonstrated to be a dominant factor for cation exchange, where different Mn2+/Cl– salts can be adopted as Mn/Cl sources and Cl-to-Cl or Cl-to-Br anion exchange is the necessary prerequisite. Such a facile synthesizing method can lead to the feasibility of tuning emissive colors for the Mn-doped CsPb(Cl/Br)3 NCs by controlling both cation and anion exchanges and open a new way to replace Pb2+ in CsPbX3 NCs by other nontoxic metal elements.

Successful development of all-inorganic CsPbX3 (X = Cl, Br, or I) perovskite quantum dots (PQDs) has been witnessed due to their unique optical and electrical properties. However, the heavy usage of Pb element in PQDs has limited the commercial application of these PQDs, and the preparation of low-Pb or Pb-free PQDs is imperative. In this study, we report room-temperature reverse synthesis of CsPbxMn1−xCl3 PDQs from CsMnCl3 precursor nanocrystals through cation exchange. Interestingly, two-step phase transformation processes from hexagonal CsMnCl3 to rhombohedral Cs4PbxMn1−xCl6 and finally to cubic CsPbxMn1−xCl3 are evidenced. With an increase in the reaction time, Mn2+ ions in the PQD lattice are gradually replaced by Pb2+ ions. Notably, Mn2+ d → d broadband luminescence is not detected for the Cs4PbxMn1−xCl6 product, but it is intense for the CsPbxMn1−xCl3 sample owing to efficient energy transfer from CsPbCl3 to Mn2+. Moreover, it is found that the introduction of Br− into the reaction system will prohibit the complete phase transformation from rhombohedral Cs4PbxMn1−x(Cl/Br)6 to cubic CsPbxMn1−x(Cl/Br)3. By controlling the ratio between the CsMnCl3 precursor and PbBr2, tunable luminescence is easily achieved due to the combined emissions from both CsPb(Cl/Br)3 PQDs and Mn2+-emitting centers.

All inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots have attracted extreme attention due to their excellent optical performance. Unfortunately, heavy usage of the toxic Pb element is still a serious problem that needs to be solved. In the present work, Mn-doped CsPbCl3 nanocrystals are successfully prepared via a facile solvothermal reaction for the first time. A high Cs-to-Pb feeding ratio is necessary to achieve pure cubic perovskite phase and the incorporation of Mn dopants into the CsPbCl3 host is highly related to the Mn-to-Pb feeding ratio. Importantly, it is demonstrated that Mn-doped CsPbCl3 NCs synthesized by the solvothermal method have better stability than those prepared by traditional hot injection. To finely adjust the bandgap of CsPbCl3 NCs, Cl-to-Br anion exchange is used to fabricate Mn-doped CsPb(Cl/Br)3 NCs with tunable multi-color luminescence. Finally, the as-prepared Mn-doped CsPb(Cl/Br)3 products are demonstrated to be applicable as color converters for constructing white light-emitting diodes and optical thermometric medium for accurate temperature sensing.

A thin SiOyNx film was inserted below a conventional SiNx antireflection coating used in c-Si solar cells in order to improve the surface passivation and the solar cell's resistance to potential-induced degradation (PID). The effect of varying the flow ratio of the N2O and SiH4 precursors and the deposition temperature for the SiOyNx thin film upon material properties were systematically investigated. An excellent surface passivation was obtained on FZ p-type polished silicon wafers, with the best results obtained with a SiOyNx film deposited at a very low temperature of 130 °C and with an optical refractive index of 1.8. In the SiOyNx/SiNx stack structure, a SiOyNx film with ~6 nm thickness is sufficient to provide excellent surface passivation with an effective surface recombination velocity Seff

Backsheet is the key element to ensure the power generation of PV modules during their whole life cycle. To continually decrease the LCOE, backsheets of new structures are gradually applied. Currently, the evaluation of module product performance is mainly on the module scale, while the assessment of each single material is rare. This paper is aimed at the evaluation of each single backsheet’s reliability when applied in different climatic environments for the widely used new backsheet structures (BS1-BS5). Through comparative research, the backsheet based on thicker PET was found to have a better mechanical performance and BS3 exhibited good resistance performance in hot and humid condition, which could be attributed to the low water vapor transmission rate of the PO film.

In this work, a three-dimensional, serpentine channel, four-cell PEM Stack model including current collector, gas diffusion layer, catalyst layer and membrane has been developed and is used to investigate the effects of membrane dehydration on PEM Stack performance. This numerical study is conducted using finite element method and computational fluid dynamics (CFD) code. To characterize the effects of membrane dehydration, the settings of operating and boundary conditions are not uniform throughout the whole period of simulation. The simulation condition is originally preferable, indicating a normally running stack in healthy status. Further transient simulation has been conducted under four failure conditions with different reactant humidity to monitor the variation of membrane water content and PEM Stack output voltage. The relatively drier reactants carry away more production water, causing the dehydration of membrane and reducing the protonic conductivity. Under a specific demand current, the output voltage of the stack decreases with the process of membrane dehydration, curtailing the maximum power that can be derived from the stack.

Polyfluorene derivative with amine side groups, namely, P1 was synthesized by the palladium-catalyzed coupling reaction of 2,5-dibromoaniline with 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9′-dioctylfluorene. Cross-linked polyazomethine P1-TPD (cross-linked polymer, P1/ terephthalic aldehyde) was obtained by the reaction of P1 with terephthalic aldehyde. Given that replacement of the phenylene ring by a thiophene ring can improve π-electron delocalization, we also synthesized P1-TPCD (cross-linked polymer, P1/ 2,5-thiophenedicarboxaldehyde) whose cross-linking bridge was a thiophene ring. The ultraviolet–visible spectra of P1-TPD showed that there was a little hypsochromic shift to its pristine polymer P1, however, the maximum emission wavelength was changed to the second peak in the photoluminescence spectra. Besides, the band gap energy ( Eg) of P1-TPD was a little narrower than that of P1. The maximum absorption wavelength and the maximum emission wavelength of P1-TPCD was almost the same with P1, but its Eg was narrower than P1 and P1-TPD. Most notably, azomethine-linked P1-TPD and P1-TPCD were fluorescent with measured fluorescent quantum yields of 22% and 44%.

Three different structural types of closed cooling tower (CCT) and two cooling water flow directions were considered. The experimental study were done on the cooling performance of influences of inlet air dry and wet bulb temperature, cooling water flow rate and inlet temperature, air flow rate and spray density. The experimental results show that the cooling performance of CCT with packing is obviously better than non-packing cooling tower in 7%~18.4%. And the cooling performance of CCT with packing on top and coil underneath is slightly better than CCT with coil on top and packing underneath in 4.9%. In the same conditions the cooling performance of CCT with packing under cooling water cocurrent-flow is better than that cooling water countercurrent-flow in 3.2%~9.6%. Therefore, the closed cooling tower structure with the cooling water path in bottom and out top, and with packing on top and coil underneath is recommended.

Microcrystalline silicon thin films prepared by plasma enhanced chemical vapor deposition (PECVD). Effects of deposition power on the microstructure properties of the thin films were investigated by Raman spectrometry, Fourier transform infrared absorption spectroscopy (FTIR) and atomic force microscopy (AFM). With increasing deposition power from 100 W to 900 W, the growth rate increased from 0.75Å/s to 2.96Å/s. The Raman spectrometry measurements showed that the peak of all films is nearby at 514 nm. The FTIR spectroscopic analysis exhibit that with power increasing the intensities of both the (Si-H)nstretching mode component at 2100cm-1and wagging mode component at 620cm-1increase. The surface morphology of the films using the AFM showed the surface roughness and voids of the films increase with deposition power increasing.

Isopropyl alcohol (IPA) is widely used as an additive to enhance the alkaline texturing process of mono-crystalline silicon solar cells currently. However, due to its low boiling point and high volatilization, some negative effects are brought into large scale production especially in stability, cost and environment. In this paper, an IPA-free texturing process was studied by using other additive instead of IPA. The influences of concentration of KOH and additive on etching rate, surface morphology and weighted reflectance were investigated. It is found that the additive has an opposite effect on etching rate and pyramid size compared to KOH. The etching rate and average pyramid size decrease with the concentration of additive increased. The best weight reflectance of 10.8% and lowest average pyramid size of 1.1 um were obtained on mono-crystalline silicon surface by an optimized solution of 1.5 wt% KOH and 1.5 wt% additive at 80oC for 20 minutes. Finally, the effects of KOH and IPA-free additive on the texturing process were also discussed in detail.

Hydrogenated silicon thin film was prepared by plasma enhanced chemical vapor deposition (PECVD). The effects of the deposition pressure on the growth rate, the photoelectronic and microstructure properties of the thin films were investigated via transmission, photo/dark conductivity, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) measurements. The results indicate that the increase of the deposition pressure increases the bandgap and the growth rate, while makes the photosensitivity get worse, decreasing from more than ~103to ~102. And at the same time, the crystalline volume fraction (Xc) in the film decreases from 70% to 61%, when the deposition pressure increases from 100 Pa to 500 Pa. The order degree of the microstructure was deteriorated with pressure increasing.

Phosphorous diffusion is typically derived from three sources: phosphorus oxychloride (POCl 3 ), sprayable phosphoric acid (H 3 PO 4 ), and printable dopant phosphorous paste. Aside from being costly, these sources tend to be harmful and can facilitate bulk contamination. Ammonium Dihydrogen Phosphate (NH 4 H 2 PO 4 :ADP) can be used in the application of doping substrate for phosphorous diffusion, which is originally introduced in this paper. ADP doping, supported by the spin-on technique, has sufficient potential to mitigate the disadvantages of other phosphorous sources. The applicability and compatibility of ADP as a phosphorous doping source in the production of silicon solar cells were demonstrated in this paper. Sheet resistance mapping shows that ADP doping generated a uniform N + emitter. The ADP solution concentration and diffusion temperature influenced the phosphorous dopant profile and sheet resistance. The adjustment of the concentration and temperature enables the control of the phosphorous dopant profile and sheet resistance. Full aluminum back-surface field silicon solar cells with an ADP-diffused N + emitter were realized in this paper through screen-printed front and back contacts on 154.8 cm 2 , 180 μm thick, and 1.5–3 Ω cm p-type Cz–Si wafers. The highest confirmed efficiency of the investigated cells was 17.97% with an open circuit voltage of 628.40 mV, short circuit current density of 36.43 mA/cm 2 , and fill factor of 78.47%. The average efficiency (10 cells) was 17.70%, which also verified the uniformity of the ADP-diffused N + emitter. Selective emitter solar cells with the best efficiency of 18.41% were thus fabricated.

Pyramidal surface is commonly used as an antireflection structure. The weighted reflectance averaged by the AM 1.5 G spectrum is about 14%. In the photovoltaic field, lowering the surface reflectivity is an important approach to improve the conversion efficiency. Black silicon surface with low reflectivity is benefit of solar cells. But conversion efficiency of black silicon solar cell is still low due to the severe surface recombination. In this paper, shallower black silicon layer was formed on the pyramidal surface. For the sample etched 1 min, the weighted reflectance is only 13.20%, and the pyramidal one is 14.10%. The layer would not deteriorate the material. Lifetime of the substrates after high temperature phosphorous diffusion is 13.35 μs higher than the pyramidal one. The mean sheet resistance is nearly the same between the pyramidal surface and the etched pyramidal surface.

Currently, a conventional two‐step method has been used to generate black silicon (BS) surfaces on silicon substrates for solar cell manufacturing. However, the performances of the solar cell made with such surface generation method are poor, because of the high surface recombination caused by deep etching in the conventional surface generation method for BS. In this work, a modified wet chemical etching solution with additives was developed. A homogeneous BS layer with random porous structure was obtained from the modified solution in only one step at room temperature. The BS layer had low reflectivity and shallow etching depth. The additive in the etch solution performs the function of pH‐modulation. After 16‐min etching, the etching depth in the samples was approximately 200 nm, and the spectrum‐weighted‐reflectivity in the range from 300 nm to 1200 nm was below 5%. BS solar cells were fabricated in the production line. The decreased etching depth can improve the electrical performance of solar cells because of the decrease in surface recombination. An efficiency of 15.63% for the modified etching BS solar cells was achieved on a large area, p‐type single crystalline silicon substrate with a 624.32‐mV open circuit voltage and a 77.88% fill factor.

Light-induced plating (LIP) techniques, which are self-aligned and are used in the fabrication of well-shaped metal grids, have been widely studied and used in solar cells, particularly in laser-doped selective emitter (LDSE) ones. However, the application of LIP techniques in standard acidic-textured multi-crystalline silicon wafers with SiN x -coated surfaces can be challenging because of the presence of some unwanted metals on the SiN x surface during the plating process. This phenomenon is called over-plating, a problem in industrial LDSE multi-crystalline Si solar cell manufacturing that this paper aims to eliminate without the addition of any new process steps. The feasibility of changing the texturing process as well as the pretreatment before plating and the deposition of SiN x to reduce over-plating was investigated. The effects of over-plating on solar cell performance were also investigated to determine the mechanism of performance degradation. The cells reached a maximum efficiency of 17.2% and an average efficiency of 17.1% on large-area, commercial-grade, p-type multi-crystalline Si substrates when the over-plating problem was eliminated.

The effective minority carrier lifetime (τeff) depends upon the quality of surface passivation, which by means of the microwave photoconductance decays (μPCD) method. The effective minority carrier lifetime (τeff) cannot reveal the real bulk lifetime of minority carriers (τb) . We have applied iodine-ethanol (I-E) treatment to silicon surface at different molar concentrations and shown that the effective concentrations ranges was 0.08mol/L~0.16 mol/L, the maximum The effective minority carrier lifetime (τeff) of n-type monocrystalline and p-type monocrystalline was 973.71μs and 362.6μs, respectively. We also accurately evaluate the bulk lifetime of minority carriers by measured with different thickness of silicon substrate.

Pyramidal texture is one traditional method to realize antireflection for c-Si solar cells, due to its low cost and simplicity. As one high efficiency silicon solar cell, amorphous/crystalline silicon heterojunction (SHJ) solar cell has attracted much attention all over the world. The heterojunction interface with very low defects and interface states is critical to the SHJ solar cell performance. In order to obtain high quality interface passivation by depositing a very thin intrinsic amorphous silicon layer on the textured Si conformally, large size pyramidal texture with no metal ion contamination is required. In this work, we utilized tetra-methyl ammonium hydroxide (TMAH) instead of NaOH in the alkaline etching to prepare pyramidal texture on N-type monocrystalline silicon to avoid the possible Na+ contamination. By optimizing the etching conditions, uniform large size pyramidal texture with pyramid size of about 10 μm was fabricated successfully. Furthermore, excellent antireflection performance was demonstrated on such textured Si surface. The average reflectance was lower than 10% in the visible and near infrared spectrum range. Such pyramidally textured Si wafers will be very suitable for SHJ solar cells.

Isopropyl alcohol(IPA) is widely used as additive to enhance surface structure and reduce the reflectivity of silicon wafers in alkaline texturing process of mono-crystalline silicon solar cells currently. However, due to its low boiling point and high volatilization, some negative effects are brought into large scale production especially in stability, cost and environment. In this paper, Dipropylene glycol(DPG) which has relative high boiling point was tried to substitute IPA as texturing solution additive. The influences of concentration of DPG and NaOH on etching rate, surface morphology and reflectance spectrum were investigated. It is obviously observed that the silicon is prevented from etching reaction by the existence of DPG. The best weight reflectance of 13.6% is obtained on mono-crystalline silicon surface by an optimized solution of 1 wt% NaOH and 1 wt% DPG at 80°C for 20 minutes. Finally, the influencing mechanism of DPG was also discussed in detail.

Cold start is a necessary function for PEMFC systems. In order to investigate the water freezing and thawing process inside PEMFC stack under subzero temperature, a 2-D transient model containing 40 cells has been developed. This model approximately estimates freezing and thawing time of each cell and shows the spatial distribution of water and ice for the purpose of analyzing the differences between single cells as well. As simulation examples, two processes under 260K ambient temperature have been studied in this paper and the results show as follows: (1)after the stack shut down, first of all, the outermost layer cell of the stack freezes before the inside cells and the freezing duration of each cells is almost the same, secondly, the freezing interval time of the outer cells is longer than the inside cells and the innermost cells almost freeze at the same time; (2) before the stack start up, heating up the membrane under two situations, one with the residual water inside and the other one has been purged after it shut down, the temperature rise of the stack with water is slower than that without water, this result indicates that the residual water would influence the cold start process.

Light-induced plating (LIP), in which the current driving the metal reduction process is derived from illuminated solar cells, is an attractive technique for solar cell metallization because of its potential simplicity. However, applying the LIP techniques on standard acidic-textured multicrystalline silicon wafers with a silicon nitride-coated surface presents a challenge. The use of a spray-on carbon-doped non-stoichiometric silicon oxide [SiO x (C)] dielectric film before nickel and silver plating can greatly reduce background plating while helping decrease the reflectance on the front of silicon solar cells. The sprayed dielectric films have low refractive indices of 1.3–1.4, depending on the annealing temperature. Simulation studies show that the SiO x (C)/SiN x dual-layer anti-reflective coating has a lower weighted reflectance against an AM 1.5 G spectrum compared with the SiN x single coating. Finally, the performance of the laser-doped solar cells with a standard SiN x as an anti-reflectance coating were compared with those with the SiO x (C)/SiN x double-layer stack. An efficiency of 16.74% on a large, commercial-grade, p-type, multicrystalline silicon substrate was achieved.

Ceria-based electrolytes have been widely researched in intermediate-temperature solid oxide fuel cell (SOFC), which might be operated at 500~600 °C. Gd0.1Ce0.9O1.95(GDC10) powders were prepared by a modified chemical co-precipitation process with Gd(NO3)3 and Ce(NO3)3 as precursors, and ammonia and hydrogen peroxide as precipitants. The precursors of GDC10 were fired at 350 °C for 2 h, then the fluorite structure cerias were identified by X-ray diffraction. The powders are well crystallized, with the size about 5 nm and surface area of 148.3 m2/g. Loading 1mol% cobalt oxide as additive, the GDC10 were succeeded to densify at 950 °C by liquid phase sintering mechanism. The grain size of 1CoGDC10 is small, about 100 nm. The electrical conductivity of samples sintered at 950 °C is about 0.01S/cm at 600 °C. The existence of cobalt oxide and smaller grain size of 1CoGDC10 don't affect the electrical conductivity.

Ceria-based electrolytes have been widely researched in intermediate-temperature solid oxide fuel cell (SOFC), which might be operated at 500–600°C. Sintering behavior with lithium oxide as sintering additive and electrical conductivity of gadolinia doped ceria (Gd 0.1 Ce 0.9 O 2-δ , GDC10) electrolyte was studied in this paper by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). As the results, the fully dense GDC10 electrolytes are obtained at a low temperature of 800°C with 2.5 mol% Li 2 O as sintering additive (called 5UGDC800). During sintering process, lithium oxides adsorbed by around GDC10 surface help to sinter at 800°C and are kept at the grain boundary of GDC10 in the end. The fine grains of 100–400 nm and high electrical conductivity of 0.014 S/cm at 600°C in 5LiGDC800 were achieved, which contributed to the lower sintering temperature and enhanced grain boundary conductivity, respectively. Lithium, staying at grain boundary, reduces the depletion of oxygen vacancies in the space charge layers and increases the oxygen vacancy concentration in the grain boundary, which leads to improve the total electrical conductivity of 5LiGDC800.

In this paper a collaborative simulation platform for proton exchange membrane fuel cell (PEMFC) power systems is presented, where the stack is simulated by a two-phase distributed parameter model and the auxiliary units by lumped parameter models. By exchanging the dynamic data between the external load/auxiliary units and PEMFC stack, dynamic simulation of PEMFC stack has been carried out during the load changes for various states associated with different characteristic variables. The internal states of the stack can be observed due to variation of external load/auxiliary units. Numerical experiments are provided for a special case with multiple cycles of load changes derived from an acceleration mode of a fuel cell vehicle. The numerical results demonstrate that the “undershoot” of output voltage is due to the response lag of the auxiliary units and liquid water accumulation in the fuel cell stack.

An off-axis external cavity with double feedback is designed to simultaneously reduce spectral bandwidth and improve the beam quality of the laser diode bar. The external cavity is made up of a high-reflection mirror and a blazed grating, where the selected spatial mode can be amplified. The grating can also provide a spectral-sensitive feedback to the laser diode bar. In addition, a half-wave plate is inserted into the grating-feedback branch to control the feedback light amount, and the output laser is taken from the grating-feedback branch. The bandwidth and the beam parameter product are respectively reduced to 0.15 nm and 283 mm·mrad for laser diode bar with the external cavity at a drive current of 16 A. The center wavelength is almost unchanged as the temperature varies, the laser

The anode substrates in the planar anode-supported solid oxide fuel cells (SOFC) were prepared by tape calendaring process, as well as the thin electrolyte films for increasing the power density of SOFCs at reduced operation temperature were fabricated by slurry-coating method. The minimization of co-firing temperature for anode and electrolyte layers was investigated by a novel three-step sintering technique in this paper. In order to obtain large three phase boundaries (TBP) at the electrolyte/anode interface, active anode layer was screen printed onto the anode substrate. Dense yttria stabilized zirconia (YSZ) thin films with a 10–15 µm thickness on porous anode substrates were successfully fabricated by slurry-coating in an YSZ suspension. These three layers were co-fired together at 1300–1350 °C. The fuel cells with a diameter of 25 mm fabricated by this co-firing technique show relatively high power density. The open circuit voltage (OCV) of 1.10 V was observed at 800 °C, the maximum power densities are 0.28, 0.51 and 0.95 W cm − 2 , at 700, 750 and 800 °C, respectively.

Constant potential method is used to synthesize polyaniline (PANI) nanofibers in a solution containing methanol. According to shaping theory, the reasons about forming polyaniline nanofibers were suggested. The effects of the synthesis parameters, such as monomer concentration, methanol concentration, HCl concentration, electrode potential, polymerization time, and reaction temperature on the morphology of the PANI films have been investigated. Scanning electron microscopy results was used to characterize the morphology of PANI nanofibers. Both UV–vis absorption spectra and FTIR spectra indicate that there exists interaction between methanol molecules and polyaniline chains.

A novel Littman-Metcalf external cavity laser diode array with two feedback mirrors is introduced. The line-width broadening effect caused by smile can be reduced by the novel external cavity. At the drive current of 16A, the line-width is narrowed to 0.1nm from free-running width of 1.6nm with output efficiency of 84%.

The application of Czochralski (Cz) monocrystalline silicon material in solar cells is limited by its high cost and serious light-induced degradation. The use of cast multicrystalline silicon is also hindered by its high dislocation densities and high surface reflectance after texturing. Mono-like crystalline silicon is a promising material because it has the advantages of both mono- and multicrystalline silicon. However, when mono-like wafers are made into cells, the efficiencies of a batch of wafers often fluctuate within a wide range of >1% (absolute). In this work, mono-like wafers are classified by a simple process and fabricated into laser doping selective emitter cells. The effect and mechanism of subgrains on the performance of mono-like crystalline silicon solar cells are studied. The results show that the efficiency of mono-like crystalline silicon solar cells significantly depends on material defects that appear as subgrains on an alkaline textured surface. These subgrains have an almost negligible effect on the optical performance, shunt resistance, and junction recombination but significantly affect the minority carrier diffusion length and quantum efficiency within a long wavelength range. Finally, an average efficiency of 18.2% is achieved on wafers with hardly any subgrain but with a small-grain band.

It is studied in this paper that the electrical characteristics of the interface between SiOyNx/SiNx stack and silicon wafer affect silicon surface passivation. The effects of precursor flow ratio and deposition temperature of the SiOyNx layer on interface parameters, such as interface state density Dit and fixed charge Qf, and the surface passivation quality of silicon are observed. Capacitance–voltage measurements reveal that inserting a thin SiOyNx layer between the SiNx and the silicon wafer can suppress Qf in the film and Dit at the interface. The positive Qf and Dit and a high surface recombination velocity in stacks are observed to increase with the introduced oxygen and minimal hydrogen in the SiOyNx film increasing. Prepared by deposition at a low temperature and a low ratio of N2O/SiH4 flow rate, the SiOyNx/SiNx stacks result in a low effective surface recombination velocity (Seff) of 6 cm/s on a p-type 1 Ωcm–5 Ωcm FZ silicon wafer. The positive relationship between Seff and Dit suggests that the saturation of the interface defect is the main passivation mechanism although the field-effect passivation provided by the fixed charges also make a contribution to it.

Thermal atomic layer-deposited (ALD) aluminum oxide (Al2O3) acquires high negative fixed charge density (Q f) and sufficiently low interface trap density after annealing, which enables excellent surface passivation for crystalline silicon. Q f can be controlled by varying the annealing temperatures. In this study, the effect of the annealing temperature of thermal ALD Al2O3 films on p-type Czochralski silicon wafers was investigated. Corona charging measurements revealed that the Q f obtained at 300°C did not significantly affect passivation. The interface-trapping density markedly increased at high annealing temperature (>600°C) and degraded the surface passivation even at a high Q f. Negatively charged or neutral vacancies were found in the samples annealed at 300°C, 500°C, and 750°C using positron annihilation techniques. The Al defect density in the bulk film and the vacancy density near the SiO x /Si interface region decreased with increased temperature. Measurement results of Q f proved that the Al vacancy of the bulk film may not be related to Q f. The defect density in the SiO x region affected the chemical passivation, but other factors may dominantly influence chemical passivation at 750°C.

In this paper, a fully coupled non-isothermal, electrochemical, and transport 3D model for a 10-cell PEMFC stack with coolant channels is constructed and implemented to examine and compare the influence factors to the stack performance. The first case to be considered is under different thermal operation conditions, including thermostatic, adiabatic, and heat exchange operation. The corresponding results show that a better uniformity and the largest stack output power density can be obtained under heat exchange operation. The other case is to compare the effects of heat transfer coefficients for different materials (ranging from 5 W/(m2·K) to 50 W/(m2·K)) on the spatial non-homogeneity of stack voltage and output power density. Numerical results indicate that the degree of the non-uniformity of individual cell voltage can be minimized, and the output power density can be elevated to a certain degree when the heat transfer coefficient is set as 25 W/(m2·K). In addition, an attempt is carried out to investigate the changes of some important variables due to the tolerance stacking or performance degradation, where we assume some cells’ contact resistance increases. We observe that a large jump of cell voltage and temperature occurs, which can be used as a detection signal for stack safety operation.

The thermal transport phenomena and mechanical effects due to thermal-inertia loading during start-up/shut-down operations in a 3D proton exchange membrane fuel cell (PEMFC) stack in a subfreezing environment are studied in this paper. Under the protection of a specific heat insulator, we investigate the time consumption problem due to thermal transport during the heating-startup/cooling-shutdown processes in order to find a way to normally restart PEMFC stack without regard to the electrochemical reaction. On the other hand, the mechanical effects due to thermal-inertia loading are illustrated as well for PEMFC stack in subfreezing environment. In the numerical simulations, we design a combined finite element/upwind finite-volume discretization to approximate the thermal transport equation for different cases of thermal transport process and a finite element approximation to solve the displacement fields of thermal/inertia-induced mechanical problem for a 3D PEMFC stack. The numerical results provide the rational guidance to preserve heat in PEMFC stack in order to start fast before electrochemical reactions occur and prevent the stack from interior and exterior mechanical damages. The optimization design for the material of PEMFC stack to reduce the remarkable mechanical effects due to inertia loading is presented as well.

A novel off-axis external cavity is designed for laser diode array to improve the beam quality. In this external cavity, a circle aperture with variable size is used as a spatial filter. The diameter of aperture is optimized to 1.2mm and the off-axis angle of external cavity is optimized at 2.6 deg. In the optimal case, the beam parameter product (BPP) of laser diode array is reduced to 121 mm.mrad from 1050 mm.mrad with external cavity optical efficiency of 81%.