Modeling the oxidative coupling of methane： Heterogeneous chemistry coupled with 3D flow field simulation

The oxidative coupling of methane (OCM) over titanate perovskite catalyst has been developed by three-dimensional numerical simulations of flow field coupled with heat transfer as well as heterogeneous kinetic model. The reaction was assumed to take place both in the gas phase and on the catalytic surface. Kinetic rate constants were experimentally obtained using a ten step kinetic model. The simulation results agree quite well with the data of OCM experiments, which were used to investigate the effect of temperature on the selectivity and conversion obtained in the methane oxidative coupling process. The conversion of methane linearly increased with temperature and the selectivity of C2 was practically constant in the temperature range of 973–1073 K. The study shows that CFD tools make it possible to implement the heterogeneous kinetic model even for high exothermic reaction such as OCM.     

Novel Quasi-solid-state Dye-sensitized Solar Cell Based on Monolayer Capped TiO2 Nanoparticles Framework Materials

Dodecylbenzenesulfonate (DBS)-capped TiO2 nanoparticles have been synthesized and employed in dye-sensitized solar cells to form a quasi-solid state electrolyte. Owing to the long alkyl-chain capping around the TiO2 nanoparticles interacting with the liquid solvent, the dye sensitized solar cell based on such DBS-capped TiO2 nanoparticle framework material gel electrolyte shows higher stability compared with the non-capped one in the long-term application and gives a comparable overall efficiency of 6.3% at AM 1.5 illumination.     

Optimizing Photovoltaic Performance by Kinetic Quenching of Layered Heterojunctions

The mixing morphology control plays a crucial role in photovoltaic power generation,yet this specific effect on device performances remains elusive.Here,we employed computational approaches to delineate the photovoltaic properties of layered heterojunction polymer solar cells with tunable mixing morphologies.One-step quench and two-step quench strategies were proposed to adjust the mixing morphology by thermodynamic and kinetic effects.The computation for the one-step quench revealed that modulating interfacial widths and interfacial roughness could significantly promote the photovoltaic performance of layered heterojunction polymer solar cells.The two-step quench can provide a buffer at a lower temperature before the kinetic quenching,leading to the formation of small-length-scale islands connected to the interface and a further increase in photovoltaic performance.Our discoveries are supported by recent experimental evidence and are anticipated to guide the design of photovoltaic materials with optimal performance.     

Rule of 100:An inherent limitation or performance measure in oxidative coupling of methane?

The oxidative coupling of methane over La 2 O 3 /CaO type-catalyst in a fixed-bed reactor is studied under a wide range of operating conditions(973相似文献   

Calculation aided miscibility manipulation enables highly efficient polythiophene:nonfullerene photovoltaic cells

Polythiophenes,with merits of low cost and high scalability of synthesis,have received growing interest in organic solar cells.To date,the best-performing polythiophene:nonfullerene solar cells exhibit typical power conversion efficiencies (PCEs) of 10%–12%,which is much lower than those employing PM6-and D18-type polymers.This inferior performance is mostly limited by the improper miscibility between polythiophene and acceptors.Efforts on engineering the molecular structure to systematically tune the miscibility are required.With the aid of group contribution calculations,the miscibility of polythiophene:nonfullerene blend system was finely tuned by varying the ratios of siloxane-terminated chains and alkyl chains in ester-substituted polythiophenes through random copolymerization.Based on a series of the polythiophene and nonfullerene acceptors,the detailed analysis of blend miscibility and performance reveals a surprising anticorrelation between the Flory-Huggins interaction parameter (χ_(aa)) and the optimal time of solvent vapor annealing for device performance across these systems.Primarily due to the slightly higher χ_(aa),the blend of PDCBT-Cl-Si5 and ITIC-Th1 results in a record-high PCE of 12.85%in polythiophene:nonfullerene solar cells.The results not only provide a calculation-guided approach for molecular design but also prove that precise control of the miscibility is an effective way to design high-performance polythiophene:nonfullerene blends and beyond.     

A chlorinated low-bandgap small-molecule acceptor for organic solar cells with 14.1% efficiency and low energy loss

A new acceptor-donor-acceptor(A-D-A) type small-molecule acceptor NCBDT-4 Cl using chlorinated end groups is reported.This new-designed molecule demonstrates wide and efficient absorption ability in the range of 600–900 nm with a narrow optical bandgap of 1.40 eV. The device based on PBDB-T-SF:NCBDT-4 Cl shows a power conversion efficiency(PCE) of 13.1%without any post-treatment, which represents the best result for all as-cast organic solar cells(OSCs) to date. After device optimizations, the PCE was further enhanced to over 14% with a high short-circuit current density(Jsc) of 22.35 m A cm-2 and a fill-factor(FF) of 74.3%. The improved performance was attributed to the more efficient photo-electron conversion process in the optimal device. To our knowledge, this outstanding efficiency of 14.1% with an energy loss as low as 0.55 eV is among the best results for all single-junction OSCs.     

Synergistic effect of fluorination on both donor and acceptor materials for high performance non-fullerene polymer solar cells with 13.5% efficiency

A high performance polymer solar cells(PSCs) based on polymer donor PM6 containing fluorinated thienyl benzodithiophene unit and n-type organic semiconductor acceptor IT-4 F containing fluorinated end-groups were developed. In addition to complementary absorption spectra(300–830 nm) with IT-4 F, the PM6 also has a deep HOMO(the highest occupied molecular) level(-5.50 e V), which will lower the open-circuit voltage(V_(oc)) sacrifice and reduce the E_(loss) of the IT-4 F-based PSCs. Moreover, the strong crystallinity of PM6 is beneficial to form favorable blend morphology and hence to suppress recombination. As a result, in comparison with the PSCs based on a non-fluorinated D/A pair of PBDB-T:ITIC with a medium PCE of 11.2%, the PM6:IT-4 Fbased PSCs yielded an impressive PCE of 13.5% due to the synergistic effect of fluorination on both donor and acceptor, which is among the highest values recorded in the literatures for PSCs to date. Furthermore, a PCE of 12.2% was remained with the active layer thickness of up to 285 nm and a high PCE of 11.4% was also obtained with a large device area of 1 cm~2. In addition, the devices also showed good storage, thermal and illumination stabilities with respect to the efficiency. These results indicate that fluorination is an effective strategy to improve the photovoltaic performance of materials, as well as the both fluorinated donor and acceptor pair-PM6:IT-4 F is an ideal candidate for the large scale roll-to-roll production of efficient PSCs in the future.     

Nano Si preparation by constant cell voltage electrolysis of FFC-Cambridge Process in molten CaCl₂

Using FFC-Cambridge Process to prepare Si from SiO2 is a promising method to prepare nanostructured and highly pure silicon for solar cells.However,the method still has many problems unsolved and the controlling effect of the cell voltage on silicon product is not clear.Here we report in this article that nano cluster-like silicon product with purity of 99.95%has been prepared by complete conversion of raw material SiO2,quartz glass plate,using constant cell voltage electrolysis FFC-Cambridge Process.By analysis of XRD,EDS,TEM,HRTEM and ICP-AES as well as the discussion from the thermodynamics calculation,the morphology and components of the product based on the change of cell voltage are clarified.It is clear that pure silicon could be prepared at the cell voltage of 1.7 2.1 V in this reaction system.The silicon material have cluster-like structure which are made of silicon nanoparticles in 20 100 nm size.Interestingly,the cluster-like nano structure of the silicon can be tuned by the used cell voltage.The purity,yield and the energy cost of silicon product prepared at the optimized cell voltage are discussed.The purity of the silicon product could be further improved,hence this method is promising for the preparation of solar grade silicon in future.     

Recent strategies to improve moisture stability in metal halide perovskites materials and devices

At present,the stability of the new generation of solar cells based on hybrid perovskites is the bottleneck for their practical applications.Photochemical effects,high temperature,ultraviolet light,humidity and other known or still unknown factors might cause reduction of effectiveness or even irreversible loss of materials properties due to decomposition of functional layers within perovskite solar cells(PSCs).These factors alone have a serious impact on each component of the device,while their combinations lead to much more complicated effects and consequences.This review focuses on the stability of PSCs and the degradation of the device in a humid environment.We assess the instability factors and deep-seated principles of evolution of the device structure in a humidity environment with the emphasis on the influence on their interrelations.The related solutions are reviewed from the perspective of the encapsulation,perovskite active layer,carrier transport layer and electrodes.Combined with the latest research,we believe that the waterproof strategy of PSCs requires either tight encapsulation or thorough modifications in the device itself.Therefore,it is important to develop feasible strategies to improve the overall device stability over humid according to the target characteristics of various devices.     

Electrochemical reduction of CO_2 in solid oxide electrolysis cells

The effort on electrochemical reduction of CO_2 to useful chemicals using the renewable energy to drive the process is growing fast recently. In this review, we introduce the recent progresses on the electrochemical reduction of CO_2 in solid oxide electrolysis cells(SOECs). At high temperature, only CO is produced with high current densities and Faradic efficiency while the reactor is complicated and a better sealing technique is urgently needed. The typical electrolytes such as zirconia-based oxides, ceria-based oxides and lanthanum gallates-based oxides, anodes and cathodes are introduced in this review, and the cathode materials, such as conventional metal–ceramics(cermets), mixed ionic and electronic conductors(MIECs) are discussed in detail. In the future, to gain more value-added products, the electrolyte, cathode and anode materials should be developed to allow SOECs to be operated at temperature range of 573–873 K. At those temperatures, SOECs may combine the advantages of the low temperature system and the high temperature system to produce various products with high current densities.     

Vapor treatment enables efficient and stable FAPbI3 perovskite solar cells

Metal halide perovskite solar cells(PSCs)have attracted extensive research interest in recent years due to their lowcost processing,high power conversion efficiency(PCE),and tunable bandgap enabling tandem photovoltaics(PVs).Over the past decade,PSCs have witnessed an impressive increase in PCEs from 3.8%to 25.5%,which is the highest among thin-film PV technologies and is comparable to those of crystalline silicon solar cells[1].     

A new kinetic model for direct CO_2 hydrogenation to higher hydrocarbons on a precipitated iron catalyst:Effect of catalyst particle size

The kinetic of the direct CO_2 hydrogenation to higher hydrocarbons via Fischer–Tropsch synthesis(FTS)and reverse water-gas shift reaction(RWGS) mechanisms over a series of precipitated Fe/Cu/K catalysts with various particle sizes was studied in a well mixed, continuous spinning basket reactor. The iron catalysts promoted with copper and potassium were prepared via precipitation technique in various alcohol/water mixtures to achieve a series of catalyst particle sizes between 38 and 14 nm. A new kinetic model for direct CO_2 hydrogenation was developed with combination of kinetic model for FTS reaction and RWGS equilibrium condition. For estimate of structure sensitivity of indirect CO_2 hydrogenation to higher hydrocarbons, the kinetic parameters of developed model are evaluated for a series of iron catalysts with various particle sizes. For kinetic study a wide range of syngas conversions have been obtained by varying experimental conditions. The results show that the new developed model fits favorably with experimental data. The values of activation energies for indirect CO_2 hydrogenation reaction are fall within the narrow range of 23–16 kJ/mol.     

Efficient solar cells based on cosensitizing porphyrin dyes containing a wrapped donor,a wrapped π-framework and a substituted benzothiadiazole unit

Three new porphyrin dyes XW45-XW47 have been synthesized employing a dialkoxy-wrapped phenothiazine donor, a tetraalkoxy-wrapped porphyrin π-framework, a benzothiadiazole(BTD)-based auxiliary acceptor, and an anchoring benzoic acid group. On the basis of our previously reported dye XW36, XW45 was synthesized by introducing a BTD unit to broaden the absorption spectrum, further introducing a hexyl-substituent into the BTD unit afforded XW46, and an additional fluorine atom was introduced to the carboxyphenyl acceptor to afford XW47. As expected, the BTD unit obviously broadens and red-shifts the absorption threshold of XW45-XW47 to ca.750 nm. Dye-sensitized solar cells(DSSCs) were fabricated based on a cobalt electrolyte using chenodeoxycholic acid(CDCA) as the coadsorbent. Under full sun illumination, XW45 exhibits an efficiency of 9.73%, which is slightly lower than that of 10.19% obtained for the reference dye SM315. By contrast, XW46 and XW47 show higher efficiencies than SM315 owing to the improved anti-aggregation ability associated with the hexyl group on the BTD unit and better ICT effect induced by the fluorine atom on the carboxyphenyl unit. Thus, XW47 exhibits the highest efficiency of 10.41% among the porphyrin dyes. Furthermore, PT-C6 was used as the cosensitizer to improve the light harvesting ability and efficiencies of the cells due to its broad absorption within 350–560 nm. Thus, high efficiencies of 10.32%, 11.38% and 10.90% were achieved for the cosensitized solar cells based on XW45–XW47, respectively, owing to the obviously enhanced photocurrent density(JSC). In addition, under 30% full sun illumination, XW46+PT-C6 exhibits a high efficiency of 13.08%. These results give an effective method for building high performance DSSCs through the cosensitization of porphyrin dyes containing a wrapped donor, a wrapped porphyrin framework and a properly substituted auxiliary benzothiadiazole unit.     

An Alternating Polymer of Two Building Blocks Based on B←N Unit:Non-fullerene Acceptor for Organic Photovoltaics

B←N coordination bond can be used to develop polymer electron acceptors for efficient all-polymer solar cells(all-PSCs). Here, we report a new alternating conjugated polymer containing two building blocks based on B←N unit. The polymer exhibits strong light absorption in the visible range, low-lying LUMO/HOMO energy levels and moderate electron mobility. The resulting all-PSC devices exhibit power conversion efficiencies of 1.50%–2.47%.     

Applying Silver Tellurite to Optimize Ag/Si Contact Interface in Silicon Solar Cells

Nowadays, researches on developing new etching materials to optimize the Ag/Si contact interface in silicon solar cells(SSCs) are rare, which alleviates the further development of SSCs. In this study, silver tellurite(Ag_2 TeO_3, monoclinic, P21/a(14)) is synthesized and developed as an excellent etching material in SSCs. The Ag_2TeO_3 displays a low starting temperature of etching Si_3N_4 of ～545 °C, which is ～160 °C lower than that of PbO. Besides, by applying Ag_2TeO_3, conductive silver nanoparticles with a length of about 300～500 nm and a thickness of ～50 nm form in the Ag/Si contact interface, which effectively reduces the Ag-Si contact resistance, and leads to a high solar cell efficiency of ～18.4%. This study opens a new window for further enhancing the solar cell efficiency in the future.     

Achieving high efficiency and low voltage loss simultaneously for non-fullerene organic solar cells

<正>Conventional organic solar cells are based on fullerene acceptors, which caused several drawbacks including poor absorption in visible and near IR regions, limited tunability of energy levels, and most importantly, large voltage loss from the optical bandgap of the cell to the open circuit voltage of the solar cell [1]. During the past few years, nonfullerene OSCs have emerged as a promising alternative to     

Preparation of CH_3NH_3PbI_3 thin films for solar cells via Vapor Transfer Method

Organometal halide perovskite based solar cells have emerged as one of the most promising candidates for low-cost and high-efficiency solar cell technologies.Here a Vapor Transfer Method(VTM)is used to fabricate high quality perovskite thin films in a balanced vacuum capsule.By adjusting the reaction temperature,CH_3NH_3I saturated vapor which then reacts with PbI_2films can be controlled and the formation process of CH_3NH_3PbI_3perovskite films can be further influenced.Prepared perovskite films which exhibit pure phase,smooth surface and high crystallinity are assembled into planar heterojunction inverted solar cells.The whole fabrication process of solar cell devices is organic solution free.Finally,the champion cell achieved power conversion efficiency(PCE)of 13.08%with negligible current–voltage hysteresis under fully open-air conditions.The photovoltaic performance could be further enhanced by optimizing perovskite composition and the device structure.     

IDENTIFICATION OF DYNAMIC BEHAVIOUR OF LIGHT-POTENTIAL TRANSDUCTION SYSTEM IN PHOTORECEPTOR OF CALLIPHORA ERYTHROCEPHALA USING IRS-STIMULI

The linear dynamic behaviour of the light-potential transduction system in photorceeptor of Calliphora erythrocephala has been studied through the cross-correlation method using InverseRepeat Sequences and the lineal model of phototransduction is provided. The impulse response function and frequency characteristics have been determiued in the condition of background illumination.The results suggest that the R1-6 is equipped with a gain and time constant control mechanism which depends upon the adaptation level of the system under study.It becomes evident that the IRS correlation method is powerful to quantify the dynamic characteristics of the system containing nonlinearities and will become a very popular application for the study of biological sensory systems.The visual receptor cells R1-6 in the fly are the most sensible choice for the study of the light-potential transdnction system of the eye. The input of the system is the temporarily varying light intensity applied upon the eyes of the fly and th     

Applying Silver Teilurite to Optimize Ag/Si Contact Interface in Silicon Solar Cells

Nowadays,researches on developing new etching materials to optimize the Ag/Si contact interface in silicon solar cells(SSCs)are rare,which alleviates the further development of SSCs.In this study,silver tellurite(Ag2 TeO3,monoclinic,P21/a(14))is synthesized and developed as an excellent etching material in SSCs.The Ag2TeO3 displays a low starting temperature of etching Si3N4 of^545°C,which is^160°C lower than that of PbO.Besides,by applying Ag2TeO3,conductive silver nanoparticles with a length of about 300~500 nm and a thickness of^50 nm form in the Ag/Si contact interface,which effectively reduces the Ag-Si contact resistance,and leads to a high solar cell efficiency of^18.4%.This study opens a new window for further enhancing the solar cell efficiency in the future.     

THERMAL DEGRADATION OF THERMOTROPIC LIQUID CRYSTALLINE TERPOLYESTERS BASED ON VANILLIC ACID, p-HYDROXYBENZOIC ACID AND POLY(ETHYLENE TEREPHTHALATE )

Nine thermotropic liquid crystalline terpolyesters based on vaniUic acid(V), p-hydroxybenzoic acid(H) and poly(ethylene terephthalate)(E) were investigated by thermogravimetry to ascertain their thermostability and the kinetic parameters for thermal degradation. Overall activation energy data of the degradation had been calculated over the range 5 ～70% weight loss. The temperatures and the activation energy of the degradation lie in the ranges of 384 ～394 ℃at a heating rate of 1℃/min and 176 ～205 KJ/mol at the weight loss of 5%, respectively, which suggests that the terpolyesters have good thermostability.