Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells sti...Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells still lacks ofa systematically understanding.In this work,the evolution of crystallographic structures,intermediate phase,ultrafast dynamics,and thermal decomposition behavior of MA-mixed perovskite FA_(1-x)MA_(x)PbI_(3)(x=0–100%)areinvestigated.The influence of MA on the stability of devices under heat,light,and humidity exposure arerevealed.In the investigated compositional space(x=0–100%),device efficiencies vary from 19.5%to 22.8%,andthe light,thermal,and humidity exposure stability of the related devices are obviously improved forFA1-xMAxPbI_(3)(x=20%–30%).Incorporation 20%–30%of MA cations lowers nucleation barrier and causes asignificant volume shrinkage,which enhances the interaction between FA and I,thus improving crystallizationand stability of the FA_(1-x)MA_(x)PbI_(3).Thermal behavior analysis reveals that the decomposition temperature of FA_(0.8)MA_(0.2)PbI_(3)reaches 247℃(FAPbI_(3),233℃)and trace amounts of MA cations enhance the thermal stability ofthe perovskite.Remarkably,we observe lattice shrinkage using spherical aberration corrected transmissionelectron microscope(AC-TEM).This work implies that stabilizing perovskites will be realized by incorporatingtrace amounts of MA,which improve the crystallization and carrier transport,leading to improved stability andperformances.展开更多
The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of ene...The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances.展开更多
By direct numerical simulations of the plane Couette flow (PCF) in a large computational domain, it is shown that an isolated turbulent band decays monotonically at low Reynolds numbers but experiences transient growt...By direct numerical simulations of the plane Couette flow (PCF) in a large computational domain, it is shown that an isolated turbulent band decays monotonically at low Reynolds numbers but experiences transient growth before the eventual relaminarization at moderate Reynolds numbers. The lower bound Reynolds number of the transient-growth regime is determined as 286. The width, length, and tilt angle of the iso- lated band structure are defined based on the disturbance kinetic energy in the mid-plane, and the geometric characteristics of the band can be described with a tilted rectangle. It is illustrated that before its eventual fragmentation, the isolated turbulent band decays in a style of longitudinal contraction, where the center, width, and tilt angle of the band keep almost constant but the band length contracts with a statistically constant velocity.展开更多
基金supported by the Nation Key R&D Program of China(Grant Numbers:2023YFC3906103)the Natural Science Foundation of Hunan Province(No.2022JJ30757)+1 种基金Entrepreneurship Research Team Project(No.1053320220430)Guangdong Science and Technology Planning Project(2018B030323010).
文摘Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells still lacks ofa systematically understanding.In this work,the evolution of crystallographic structures,intermediate phase,ultrafast dynamics,and thermal decomposition behavior of MA-mixed perovskite FA_(1-x)MA_(x)PbI_(3)(x=0–100%)areinvestigated.The influence of MA on the stability of devices under heat,light,and humidity exposure arerevealed.In the investigated compositional space(x=0–100%),device efficiencies vary from 19.5%to 22.8%,andthe light,thermal,and humidity exposure stability of the related devices are obviously improved forFA1-xMAxPbI_(3)(x=20%–30%).Incorporation 20%–30%of MA cations lowers nucleation barrier and causes asignificant volume shrinkage,which enhances the interaction between FA and I,thus improving crystallizationand stability of the FA_(1-x)MA_(x)PbI_(3).Thermal behavior analysis reveals that the decomposition temperature of FA_(0.8)MA_(0.2)PbI_(3)reaches 247℃(FAPbI_(3),233℃)and trace amounts of MA cations enhance the thermal stability ofthe perovskite.Remarkably,we observe lattice shrinkage using spherical aberration corrected transmissionelectron microscope(AC-TEM).This work implies that stabilizing perovskites will be realized by incorporatingtrace amounts of MA,which improve the crystallization and carrier transport,leading to improved stability andperformances.
基金Project supported by the National Natural Science Foundation of China(Nos.11225209,11490553,and 11521091)
文摘The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances.
基金Project supported by the National Natural Science Foundation of China(Nos.91752203,11490553,and 11602148)
文摘By direct numerical simulations of the plane Couette flow (PCF) in a large computational domain, it is shown that an isolated turbulent band decays monotonically at low Reynolds numbers but experiences transient growth before the eventual relaminarization at moderate Reynolds numbers. The lower bound Reynolds number of the transient-growth regime is determined as 286. The width, length, and tilt angle of the iso- lated band structure are defined based on the disturbance kinetic energy in the mid-plane, and the geometric characteristics of the band can be described with a tilted rectangle. It is illustrated that before its eventual fragmentation, the isolated turbulent band decays in a style of longitudinal contraction, where the center, width, and tilt angle of the band keep almost constant but the band length contracts with a statistically constant velocity.
