The paper extends weighted essentially non-oscillatory(WENO)schemes to two-dimensional quadrilateral and mixed-element unstructured meshes.The key element of the proposed methods is a reconstruction procedure suitable...The paper extends weighted essentially non-oscillatory(WENO)schemes to two-dimensional quadrilateral and mixed-element unstructured meshes.The key element of the proposed methods is a reconstruction procedure suitable for arbitrarilyshaped cells.The resulting schemes achieve the designed uniformly high-order of accuracy and compute discontinuous solutions without spurious oscillations at interfaces between cells of two different types.展开更多
High-efficiency solar cells often require light absorbers prepared from alloys, such as Cd Te_(1-x)Se_(x),CuIn_(x)Ga_(1-x)Se_(2), Cu_(2)ZnSnS_(4-x)Se_(x), and(Cs_(x)FA_(1-x))Pb(I_(1-y)Br_(y))_(3). However, how alloyin...High-efficiency solar cells often require light absorbers prepared from alloys, such as Cd Te_(1-x)Se_(x),CuIn_(x)Ga_(1-x)Se_(2), Cu_(2)ZnSnS_(4-x)Se_(x), and(Cs_(x)FA_(1-x))Pb(I_(1-y)Br_(y))_(3). However, how alloying affects solar cell performance is poorly understood, and determining common features associated with alloying is of significant interest. Herein, we studied the correlation between the A/X site compositional ratio and the photogenerated carrier dynamics using mixed halide perovskites(Cs_(x)FA_(1-x))Pb(I_(1-y)Br_(y))_(3)as examples.Nonadiabatic molecular dynamics calculations demonstrated that charge carrier recombination is highly sensitive to the compositional ratio at the A/X-site. The enhanced lifetime is attributable to the suppression of atomic fluctuations, the weakening of electron-phonon coupling, and a reduction in the electrontransition probability between band edges. The optimal Br concentration was determined to be ~18%, in agreement with experimental observations. This study not only advances our understanding of why mixed perovskites usually exhibit superior experimental photoelectric properties, but also provides a route for optimizing the carrier lifetimes and efficiencies of perovskite solar cells.展开更多
An implicit high-order accurate method for solving model kinetic equations is proposed.The method is an extension of earlier work on the construction of an explicit TVD method for hybrid unstructured meshes in physica...An implicit high-order accurate method for solving model kinetic equations is proposed.The method is an extension of earlier work on the construction of an explicit TVD method for hybrid unstructured meshes in physical space and is illustrated on the Poiseuille flow of rarefied gas.Examples of calculations are provided for different Knudsen numbers and mesh resolutions,which illustrate the efficiency and high accuracy of the new scheme.展开更多
The paper is devoted to the development of an efficient deterministic framework for modelling of three-dimensional rarefied gas flows on the basis of the numerical solution of the Boltzmann kinetic equation with the m...The paper is devoted to the development of an efficient deterministic framework for modelling of three-dimensional rarefied gas flows on the basis of the numerical solution of the Boltzmann kinetic equation with the model collision integrals.The framework consists of a high-order accurate implicit advection scheme on arbitrary unstructuredmeshes,the conservative procedure for the calculation of themodel collision integral and efficient implementation on parallel machines.The main application area of the suggested methods is micro-scale flows.Performance of the proposed approach is demonstrated on a rarefied gas flow through the finite-length circular pipe.The results show good accuracy of the proposed algorithm across all flow regimes and its high efficiency and excellent parallel scalability for up to 512 cores.展开更多
文摘The paper extends weighted essentially non-oscillatory(WENO)schemes to two-dimensional quadrilateral and mixed-element unstructured meshes.The key element of the proposed methods is a reconstruction procedure suitable for arbitrarilyshaped cells.The resulting schemes achieve the designed uniformly high-order of accuracy and compute discontinuous solutions without spurious oscillations at interfaces between cells of two different types.
基金support from the National Key Research and Development Program of China(2020YFB1506400)the National Natural Science Foundation of China (11974257)+3 种基金Jiangsu Distinguished Young Talent Funding (BK20200003)the Yunnan Provincial Key S&T Program(202002AB080001-1)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)support from the China Postdoctoral Science Foundation (2020M671570)。
文摘High-efficiency solar cells often require light absorbers prepared from alloys, such as Cd Te_(1-x)Se_(x),CuIn_(x)Ga_(1-x)Se_(2), Cu_(2)ZnSnS_(4-x)Se_(x), and(Cs_(x)FA_(1-x))Pb(I_(1-y)Br_(y))_(3). However, how alloying affects solar cell performance is poorly understood, and determining common features associated with alloying is of significant interest. Herein, we studied the correlation between the A/X site compositional ratio and the photogenerated carrier dynamics using mixed halide perovskites(Cs_(x)FA_(1-x))Pb(I_(1-y)Br_(y))_(3)as examples.Nonadiabatic molecular dynamics calculations demonstrated that charge carrier recombination is highly sensitive to the compositional ratio at the A/X-site. The enhanced lifetime is attributable to the suppression of atomic fluctuations, the weakening of electron-phonon coupling, and a reduction in the electrontransition probability between band edges. The optimal Br concentration was determined to be ~18%, in agreement with experimental observations. This study not only advances our understanding of why mixed perovskites usually exhibit superior experimental photoelectric properties, but also provides a route for optimizing the carrier lifetimes and efficiencies of perovskite solar cells.
文摘An implicit high-order accurate method for solving model kinetic equations is proposed.The method is an extension of earlier work on the construction of an explicit TVD method for hybrid unstructured meshes in physical space and is illustrated on the Poiseuille flow of rarefied gas.Examples of calculations are provided for different Knudsen numbers and mesh resolutions,which illustrate the efficiency and high accuracy of the new scheme.
基金This work was supported by the Russian Foundation for Basic Research,project no.10-01-00721-a.The author would also like to thank Dr.Les Oswald from the IT department of Cranfield University for his help with running large-scale parallel simulations on university’s HPC facility Astral and anonymous reviewers whose critical comments helped to improve the paper.
文摘The paper is devoted to the development of an efficient deterministic framework for modelling of three-dimensional rarefied gas flows on the basis of the numerical solution of the Boltzmann kinetic equation with the model collision integrals.The framework consists of a high-order accurate implicit advection scheme on arbitrary unstructuredmeshes,the conservative procedure for the calculation of themodel collision integral and efficient implementation on parallel machines.The main application area of the suggested methods is micro-scale flows.Performance of the proposed approach is demonstrated on a rarefied gas flow through the finite-length circular pipe.The results show good accuracy of the proposed algorithm across all flow regimes and its high efficiency and excellent parallel scalability for up to 512 cores.
