Perovskite solar cells are known to have a power conversion efficiency dependent on subtle variation in chemical composition and crystal and microstructures of materials,processing conditions,and device fabrication pr...Perovskite solar cells are known to have a power conversion efficiency dependent on subtle variation in chemical composition and crystal and microstructures of materials,processing conditions,and device fabrication procedures and conditions.The present work demonstrates such strong dependence of power conversion efficiency on a TiO_2 film made of the same sol with various aging time.A dense and conformal TiO_2 film was prepared by sol-gel method,and the influences of its surface morphology and thickness on performance of perovskite solar cells have been investigated.The surface morphology and thickness of the TiO_2 film were tuned by adjusting the aging time of sol,resulting in enhanced short-circuit current density and fill factor of the perovskite solar cells due to increased coverage and roughness of perovskite films,light refraction,and effective charge recombination blocking effect,which were verified by means of the light absorption spectra,photoluminescence of perovskite films with and without hole transport layer,cyclic voltammogram,and electrochemical impedance spectra.The cells with a dense and conformal TiO_2 compact layer derived from the sol aged for 4 h exhibit a power conversion efficiency of 15.7%,50% higher than the efficiency based on TiO_2 layer derived from 0 h aging sol and 3 times of the efficiency with TiO_2 layer made from 8 h aged sol.展开更多
The tungsten trioxide（WO3） thin films were firstly prepared by spin-coating-pyrolysis methods using the ammonium metatungstate（（NH4）6H2W12O40）DMF/water solution, and successfully applied as the efficient compact...The tungsten trioxide（WO3） thin films were firstly prepared by spin-coating-pyrolysis methods using the ammonium metatungstate（（NH4）6H2W12O40）DMF/water solution, and successfully applied as the efficient compact layers for the planar perovskite solar cells. The influence of the WO3 film thickness and the rinsing treatment of CH_3NH_3 PbI_3 thin film with isopropanol on the photovoltaic performance of the corresponding perovskite solar cells was systematically investigated. The results revealed that the perovskite solar cell with a 62 nm thick WO3 compact layer achieved a photoelectric conversion efficiency of 5.72%, with a short circuit photocurrent density of 17.39 mA/cm^2, an open circuit voltage of 0.58 V and a fill factor of 0.57. The photoelectric conversion efficiency was improved from 5.72% to 7.04% by the isopropanol rinsing treatment.展开更多
Berau Basin, a sub-basin of Tarakan Basin, had been developed during Eocene to Miocene period. Rocks in Berau Basin consist of sedimentary, volcanic and igneous rocks aged from Pre-tertiary until Quaternary epoch. The...Berau Basin, a sub-basin of Tarakan Basin, had been developed during Eocene to Miocene period. Rocks in Berau Basin consist of sedimentary, volcanic and igneous rocks aged from Pre-tertiary until Quaternary epoch. The youngest identified rock formation was alluvial deposit consists of mud, silt, sand, gravel and swamp with brown to dark color. This youngest rock formation is relatively weak geological condition and can cause problems in the coal mining operation. PT Berau Coal as one of the coal mining companies in Berau Basin area had experienced some problems related to the occurrence of alluvial deposit. A large failure has occurred at one of its out pit dumping?area which lies over the swamp material. The failure caused a higher operating cost since it made that the distance for waste rock dumping became to be farther than the designated area. Therefore, in order to prevent similar failure occurring at dumping area which lies above swamp material, an improvement of dumping site stability on weak geological condition has to be needed. The proposed method for improving the stability of out pit dumping area in weak geological condition is to construct the compacted layer of waste rock before the out pit dumping area construction. Based on experimental results, a minimum of 40 kPa pressure is needed to give a proper compaction to the waste rock. The result of numerical analysis by Finite Element Method (FEM) shows that construction of compacted layer on the base of out pit dumping area can improve its stability.展开更多
Observations of microstructure of explosive compacts made of Al or Al-Li alloy powders by atomization with water,nitrogen or ultrasoic Ar gas were carried out under optical and scanning electron microscopes.The rsults...Observations of microstructure of explosive compacts made of Al or Al-Li alloy powders by atomization with water,nitrogen or ultrasoic Ar gas were carried out under optical and scanning electron microscopes.The rsults indicate that super quality explosive compact can only be obtained by powders of which the thickness of the oxide layer is less than 30 nm.展开更多
Investigation of the physical and mechanical properties of snow has long been a topic of interest to researchers as the construction of compacted-snow runways in Antarctica developed. In an attempt to assess the stren...Investigation of the physical and mechanical properties of snow has long been a topic of interest to researchers as the construction of compacted-snow runways in Antarctica developed. In an attempt to assess the strength of layered compacted seasonal snow, penetration tests using modified Rammsonde were conducted in Harbin, China in early 2018. Compared with previous models, the modified Rammsonde is lighter overall, with improved resolution;thus, it is more suitable for seasonal snow;the mechanical structure was adjusted, and the reading of depth data is more convenient. A total of 74 penetration tests were carried out and the results were analyzed both qualitatively and quantitatively. The results of these analyses demonstrated the applicability of the device, and revealed that several factors affect the cone penetrometer's estimate of the strength of the layered compacted seasonal snow. Such factors include the confining pressure, penetration energy, and the snow material properties, particularly the compaction of the snow undergoing penetration. A linear relationship between the penetration pressure and snow density was also established. The effect of age hardening on the penetration pressure was studied and the microstructure of the snow particles was observed through a microscope. These analyses showed that the cone penetrometer and data processing methodology applied in this study enable a rapid estimate of strength in seasonal snow, and may be applied in Antarctica after further modification. This would provide a scientific basis for the design of China's Antarctic ice sheet airport.展开更多
In this paper, a high order compact difference scheme and a multigrid method are proposed for solving two-dimensional (2D) elliptic problems with variable coefficients and interior/boundary layers on nonuniform grids....In this paper, a high order compact difference scheme and a multigrid method are proposed for solving two-dimensional (2D) elliptic problems with variable coefficients and interior/boundary layers on nonuniform grids. Firstly, the original equation is transformed from the physical domain (with a nonuniform mesh) to the computational domain (with a uniform mesh) by using a coordinate transformation. Then, a fourth order compact difference scheme is proposed to solve the transformed elliptic equation on uniform girds. After that, a multigrid method is employed to solve the linear algebraic system arising from the difference equation. At last, the numerical experiments on some elliptic problems with interior/boundary layers are conducted to show high accuracy and high efficiency of the present method.展开更多
The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,an...The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.展开更多
Using the idea of general resonant triad of the hydrodynamic stability, the theoretical models for coherent structures in the wall region of a turbulent boundary layer is proposed. The interaction between coherent str...Using the idea of general resonant triad of the hydrodynamic stability, the theoretical models for coherent structures in the wall region of a turbulent boundary layer is proposed. The interaction between coherent structures in the wall region of a turbulent boundary layer is studied by combining the compact finite differences of high numerical accuracy and the Fourier spectral hybrid method for solving the three dimensional Navier Stokes equations. In this method, the third order mixed explicit implicit scheme is employed for the time integration. The fifth order upwind compact finite difference schemes for the nonlinear convection terms in the physical space, and the sixth order center compact schemes for the derivatives in spectral space are descried, respectively. The fourth order compact schemes satisfied by the velocities and pressure in spectral space is derived. As an application, the method is implemented to the wall region of a turbulent boundary to study the interaction between coherent structures. It is found that the numerical results are satisfactory.展开更多
The nonlinear evolution problem in nonparallel boundary layer stability was studied. The relative parabolized stability equations of nonlinear nonparallel boundary layer were derived. The developed numerical method, w...The nonlinear evolution problem in nonparallel boundary layer stability was studied. The relative parabolized stability equations of nonlinear nonparallel boundary layer were derived. The developed numerical method, which is very effective, was used to study the nonlinear evolution. of T-S disturbance wave at finite amplitudes. Solving nonlinear equations of different modes by using predictor-corrector and iterative approach, which is uncoupled between modes, improving computational accuracy by using high order compact differential scheme, satisfying normalization condition I determining tables of nonlinear terms at different modes, and implementing stably the spatial marching, were included in this method. With different initial amplitudes, the nonlinear evolution of T-S wave was studied. The nonlinear nonparallel results of examples compare with data of direct numerical simulations (DNS) using full Navier-Stokes equations.展开更多
基金supported by the"Thousands Talents"program for pioneer researcher and his innovation team,Chinathe National Natural Science Foundation of China(51374029 and 91433102)+1 种基金the Program for New Century Excellent Talents in the University(NCET-13-0668)the Fundamental Research Funds for the Central Universities(FRF-TP-14-008C1)
文摘Perovskite solar cells are known to have a power conversion efficiency dependent on subtle variation in chemical composition and crystal and microstructures of materials,processing conditions,and device fabrication procedures and conditions.The present work demonstrates such strong dependence of power conversion efficiency on a TiO_2 film made of the same sol with various aging time.A dense and conformal TiO_2 film was prepared by sol-gel method,and the influences of its surface morphology and thickness on performance of perovskite solar cells have been investigated.The surface morphology and thickness of the TiO_2 film were tuned by adjusting the aging time of sol,resulting in enhanced short-circuit current density and fill factor of the perovskite solar cells due to increased coverage and roughness of perovskite films,light refraction,and effective charge recombination blocking effect,which were verified by means of the light absorption spectra,photoluminescence of perovskite films with and without hole transport layer,cyclic voltammogram,and electrochemical impedance spectra.The cells with a dense and conformal TiO_2 compact layer derived from the sol aged for 4 h exhibit a power conversion efficiency of 15.7%,50% higher than the efficiency based on TiO_2 layer derived from 0 h aging sol and 3 times of the efficiency with TiO_2 layer made from 8 h aged sol.
基金Project supported by the National Natural Science Foundation of China(Nos.51472071,512720616,51072043)the National Basic Research Program of China(No.2011CBA00700)
文摘The tungsten trioxide（WO3） thin films were firstly prepared by spin-coating-pyrolysis methods using the ammonium metatungstate（（NH4）6H2W12O40）DMF/water solution, and successfully applied as the efficient compact layers for the planar perovskite solar cells. The influence of the WO3 film thickness and the rinsing treatment of CH_3NH_3 PbI_3 thin film with isopropanol on the photovoltaic performance of the corresponding perovskite solar cells was systematically investigated. The results revealed that the perovskite solar cell with a 62 nm thick WO3 compact layer achieved a photoelectric conversion efficiency of 5.72%, with a short circuit photocurrent density of 17.39 mA/cm^2, an open circuit voltage of 0.58 V and a fill factor of 0.57. The photoelectric conversion efficiency was improved from 5.72% to 7.04% by the isopropanol rinsing treatment.
文摘Berau Basin, a sub-basin of Tarakan Basin, had been developed during Eocene to Miocene period. Rocks in Berau Basin consist of sedimentary, volcanic and igneous rocks aged from Pre-tertiary until Quaternary epoch. The youngest identified rock formation was alluvial deposit consists of mud, silt, sand, gravel and swamp with brown to dark color. This youngest rock formation is relatively weak geological condition and can cause problems in the coal mining operation. PT Berau Coal as one of the coal mining companies in Berau Basin area had experienced some problems related to the occurrence of alluvial deposit. A large failure has occurred at one of its out pit dumping?area which lies over the swamp material. The failure caused a higher operating cost since it made that the distance for waste rock dumping became to be farther than the designated area. Therefore, in order to prevent similar failure occurring at dumping area which lies above swamp material, an improvement of dumping site stability on weak geological condition has to be needed. The proposed method for improving the stability of out pit dumping area in weak geological condition is to construct the compacted layer of waste rock before the out pit dumping area construction. Based on experimental results, a minimum of 40 kPa pressure is needed to give a proper compaction to the waste rock. The result of numerical analysis by Finite Element Method (FEM) shows that construction of compacted layer on the base of out pit dumping area can improve its stability.
文摘Observations of microstructure of explosive compacts made of Al or Al-Li alloy powders by atomization with water,nitrogen or ultrasoic Ar gas were carried out under optical and scanning electron microscopes.The rsults indicate that super quality explosive compact can only be obtained by powders of which the thickness of the oxide layer is less than 30 nm.
基金supported by the National Natural Science Foundation of China (Grant nos.41676187 and 41876213)
文摘Investigation of the physical and mechanical properties of snow has long been a topic of interest to researchers as the construction of compacted-snow runways in Antarctica developed. In an attempt to assess the strength of layered compacted seasonal snow, penetration tests using modified Rammsonde were conducted in Harbin, China in early 2018. Compared with previous models, the modified Rammsonde is lighter overall, with improved resolution;thus, it is more suitable for seasonal snow;the mechanical structure was adjusted, and the reading of depth data is more convenient. A total of 74 penetration tests were carried out and the results were analyzed both qualitatively and quantitatively. The results of these analyses demonstrated the applicability of the device, and revealed that several factors affect the cone penetrometer's estimate of the strength of the layered compacted seasonal snow. Such factors include the confining pressure, penetration energy, and the snow material properties, particularly the compaction of the snow undergoing penetration. A linear relationship between the penetration pressure and snow density was also established. The effect of age hardening on the penetration pressure was studied and the microstructure of the snow particles was observed through a microscope. These analyses showed that the cone penetrometer and data processing methodology applied in this study enable a rapid estimate of strength in seasonal snow, and may be applied in Antarctica after further modification. This would provide a scientific basis for the design of China's Antarctic ice sheet airport.
文摘In this paper, a high order compact difference scheme and a multigrid method are proposed for solving two-dimensional (2D) elliptic problems with variable coefficients and interior/boundary layers on nonuniform grids. Firstly, the original equation is transformed from the physical domain (with a nonuniform mesh) to the computational domain (with a uniform mesh) by using a coordinate transformation. Then, a fourth order compact difference scheme is proposed to solve the transformed elliptic equation on uniform girds. After that, a multigrid method is employed to solve the linear algebraic system arising from the difference equation. At last, the numerical experiments on some elliptic problems with interior/boundary layers are conducted to show high accuracy and high efficiency of the present method.
基金supported in part by the Research and Study Project of Tokai University General Research Organization and by the Grant-in-Aid for Scientific Research Grant Number 20H02838the Universiti Kebangsaan Malaysia for supporting this study through FRGS/1/2017/TK07/UKM/02/9 Grantsupported by the Research Grants Council of Hong Kong,China(Project Number:152093/18E).
文摘The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.
文摘Using the idea of general resonant triad of the hydrodynamic stability, the theoretical models for coherent structures in the wall region of a turbulent boundary layer is proposed. The interaction between coherent structures in the wall region of a turbulent boundary layer is studied by combining the compact finite differences of high numerical accuracy and the Fourier spectral hybrid method for solving the three dimensional Navier Stokes equations. In this method, the third order mixed explicit implicit scheme is employed for the time integration. The fifth order upwind compact finite difference schemes for the nonlinear convection terms in the physical space, and the sixth order center compact schemes for the derivatives in spectral space are descried, respectively. The fourth order compact schemes satisfied by the velocities and pressure in spectral space is derived. As an application, the method is implemented to the wall region of a turbulent boundary to study the interaction between coherent structures. It is found that the numerical results are satisfactory.
文摘The nonlinear evolution problem in nonparallel boundary layer stability was studied. The relative parabolized stability equations of nonlinear nonparallel boundary layer were derived. The developed numerical method, which is very effective, was used to study the nonlinear evolution. of T-S disturbance wave at finite amplitudes. Solving nonlinear equations of different modes by using predictor-corrector and iterative approach, which is uncoupled between modes, improving computational accuracy by using high order compact differential scheme, satisfying normalization condition I determining tables of nonlinear terms at different modes, and implementing stably the spatial marching, were included in this method. With different initial amplitudes, the nonlinear evolution of T-S wave was studied. The nonlinear nonparallel results of examples compare with data of direct numerical simulations (DNS) using full Navier-Stokes equations.
