Flexible strain sensor devices were fabricated by depositing Pd nanoclusters on PET membranes patterned with interdigital electrodes. The sensors responded to the deformation of the PET membranes with the conductance ...Flexible strain sensor devices were fabricated by depositing Pd nanoclusters on PET membranes patterned with interdigital electrodes. The sensors responded to the deformation of the PET membranes with the conductance changes of the nanocluster films and were characterized by both high gauge factor and wide detection range. The response characteristics of the strain sensors were found to depend strongly on the nanocluster coverage, which was attributed to the percolative nature of the electron transport in the closely spaced nanocluster arrays. By controlling the nanocluster deposition process, a strain sensor composed of nanocluster arrays with a coverage close to the effective percolation threshold was fabricated. The sensor device showed a linear response with a stable gauge factor of 55 for the applied strains from the lower detection limit up to 0.3%. At higher applied strains, a gauge factor as high as 200 was shown. The nanocluster films also demonstrated the ability to response to large deformations up to 8% applied strain, with an extremely high gauge factor of 3500.展开更多
Abstract A refined one of our exactly solvable trapezoidal barrier potential model [Thin Solids Films, 414 （2002） 136）] for metal-insulator-metal tunnel junctions has Seen presented. According to the refined model,...Abstract A refined one of our exactly solvable trapezoidal barrier potential model [Thin Solids Films, 414 （2002） 136）] for metal-insulator-metal tunnel junctions has Seen presented. According to the refined model, the longitudinal kinetic energy （ExL） and the effective mass （m^＊L） of the electron8 in the electrode on the left of the barrier distinguish from that on the right. It is found that as ExL is greater than the shorter side of the resultant trapezoidal barrier potential, there will be a coexistence of the tunneling and propagating in the barrier. The results demonstrate that the damped oscillating electron waves localized in the propagating barrier subregion lead to the oscillation and enhancement in the transmission coefficient DT and dwell time TD. For the barrier height φ1=2.6 eV and φ2 = 1.4 eV, the width d=22 A and ExL = 1.0 eV, DT and TD have a maximum of 0.054 and 0.58x10^-15 s at V = 2.04 V and 2.18 V, respectively. This suggests that a real tunneling may be a hybrid.展开更多
While the preferential movement of water inside carbon nanotube is appealing for water purification,our understanding of the water transport mechanism through carbon nanotube(CNT)-based membrane is far from adequate. ...While the preferential movement of water inside carbon nanotube is appealing for water purification,our understanding of the water transport mechanism through carbon nanotube(CNT)-based membrane is far from adequate. Here we conducted molecular dynamics simulations to study how the alignment of the CNTs in the membrane affects the water transport through the CNT membrane. It was shown that compared to the conventional CNT membrane where the alignment of CNTs was vertical to membrane surface, the ‘‘italicized CNT membrane'' in which the contact angel between membrane surface and the CNT alignment is not 90° offered a higher transmembrane flux of water. The expanded exposure of more carbon atoms to water molecules reduced the energy barrier near the entrance of this italicized CNT membrane, compared to the vertical one. For water flows through the italicized CNT membrane, the Lennard-Jones interaction between water and nanotube as function of central path of the CNT changes from ‘‘U'' to ‘‘V'' pattern, which significantly lowers energy barrier for filling water into the CNT,favoring the water transport inside carbon nanotube. Above simulation indicates new opportunities for applying CNT in water purification or related fields in which water transport matters.展开更多
The hole and electron mobilities of the amorphous films of the organic semiconductor 4,4′-N,N′-dicarbazole-biphenyl (CBP) at different electric fields were measured through the time of flight (TOF) method. Based on ...The hole and electron mobilities of the amorphous films of the organic semiconductor 4,4′-N,N′-dicarbazole-biphenyl (CBP) at different electric fields were measured through the time of flight (TOF) method. Based on its crystalline structure, the hole and electron mobilities of CBP were calculated. A detailed comparison between experimental and theoretical results is necessary for further understanding its charge transport properties. In order to do this, charge mobilities at zero electric field, μ(0), were deduced from experimental data as a link between experimental and theoretical data. It was found that the electron transport of CBP is less affected by traps compared with its hole transport. This unusual phenomenon can be understood through the distributions of frontier molecular orbitals. We showed that designing materials with frontier molecular orbitals localized at the center of the molecule has the potency to reduce the influence of traps on charge transport and provide new insights into designing high mobility charge transport materials.展开更多
The mechanism of heat transfer enhancement by liquid film on the channel walls has been investigated in laminar mixed convective flows. The temperature distribution, velocity and mass fraction distributions, and the e...The mechanism of heat transfer enhancement by liquid film on the channel walls has been investigated in laminar mixed convective flows. The temperature distribution, velocity and mass fraction distributions, and the effects of the wetted wall temperatures and the Reynolds number on the momentum,heat and mass transfer were examined in details. Results show that the liquid film can enhance heat transfer along the wetted walls by 5-10 times.展开更多
Effective electron selective layer （ESL） is critical for the power conversion efficiency in organometal halide- based perovskite solar cells （PSCs）. In this work, a spincoating process has been developed to fabric...Effective electron selective layer （ESL） is critical for the power conversion efficiency in organometal halide- based perovskite solar cells （PSCs）. In this work, a spincoating process has been developed to fabricate high quality nanocrystalline SnO2 film at 100℃ without further sintering at higher temperature. When used as ESL in PSCs, such SnO2 film shows greater electron extraction ability and higher efficiency than TiO2 film processed under similar condition, as evidenced by the efficient time-resolved photoluminescence （TRPL） quenching SnO2/CH3NH3PbI3 film. As a resuit, the SnO2-based PSCs possess higher open circuit voltage of 0.91 V, short circuit current density of 20.73 mA cm^-2, and fill factor of 64.25%, corresponding to a conversion efficiency of 12.10%, compared with 7.16% of TiO2-based PSCs. This demonstrates the great potential of applying spin-coating sintering-free process for the low-cost and large-scale manufacturing of PSCs.展开更多
Two-dimensional(2D)Dion-Jacobson(D-J)-type cesium lead iodide CsPbI_(3) perform remarkably in terms of stability.However,the complex interactions between spacer and inorganic layers limit its excellent progress in per...Two-dimensional(2D)Dion-Jacobson(D-J)-type cesium lead iodide CsPbI_(3) perform remarkably in terms of stability.However,the complex interactions between spacer and inorganic layers limit its excellent progress in perovskite solar cells(PSCs).Herein,starting from the considerable structural diversity of organic spacers,we engineer 2D CsPbI_(3) with fine-tuning functionalities.Specifically,for the first time we embedded fluorinated aromatic cations in 2D D-J CsPbI_(3),and successfully applied it into construction of high-performance PSCs.Compared with constitutive 1,4-diaminobenzene(PDA),the fluorinated 2-fluorobenzene-1,4-diamine(F-PDA)component greatly expands the dipole moment from 0.59 D to 3.47 D,which reduces the exciton binding energy of the system.A theoretical study shows that the spacer layer and inorganic plane are more enriched with charge accumulation in(F-PDA)Csn±1 Pb_(n)I_(3n+1).The results show that(F-PDA)Csn±1Pb_(n)I_(3n+1) demonstrates more significant charge transfer between organic and inorganic layers than(PDA)Csn±1 Pb_(n)I_(3n+1),and it is confirmed in the femtosecond transient absorption experiment.Moreover,the interactions of the fluorinated spacer with the[PbI_(6)]_(4)-plane effectively manipulate the crystallization quality,and thus the ion migration and defect formation of target 2D CsPbI_(3) are inhibited.As a result,we obtained a record power conversion efficiency(PCE)beyond 15%for 2D D-J(F-PDA)Cs_(3)Pb_(4)I_(13)(n=4)PSCs with significantly improved environmental stability compared with the three-dimensional(3D)counterparts.展开更多
基金supported by the National Natural Science Foundation of China(No.11627806)a Project funded by the Priority Academic Programme Development of Jiangsu Higher Education Institutions
文摘Flexible strain sensor devices were fabricated by depositing Pd nanoclusters on PET membranes patterned with interdigital electrodes. The sensors responded to the deformation of the PET membranes with the conductance changes of the nanocluster films and were characterized by both high gauge factor and wide detection range. The response characteristics of the strain sensors were found to depend strongly on the nanocluster coverage, which was attributed to the percolative nature of the electron transport in the closely spaced nanocluster arrays. By controlling the nanocluster deposition process, a strain sensor composed of nanocluster arrays with a coverage close to the effective percolation threshold was fabricated. The sensor device showed a linear response with a stable gauge factor of 55 for the applied strains from the lower detection limit up to 0.3%. At higher applied strains, a gauge factor as high as 200 was shown. The nanocluster films also demonstrated the ability to response to large deformations up to 8% applied strain, with an extremely high gauge factor of 3500.
基金Supported by the Science and Technology Foundation of Shenzhen under Grant Nos. 200604 and 200606
文摘Abstract A refined one of our exactly solvable trapezoidal barrier potential model [Thin Solids Films, 414 （2002） 136）] for metal-insulator-metal tunnel junctions has Seen presented. According to the refined model, the longitudinal kinetic energy （ExL） and the effective mass （m^＊L） of the electron8 in the electrode on the left of the barrier distinguish from that on the right. It is found that as ExL is greater than the shorter side of the resultant trapezoidal barrier potential, there will be a coexistence of the tunneling and propagating in the barrier. The results demonstrate that the damped oscillating electron waves localized in the propagating barrier subregion lead to the oscillation and enhancement in the transmission coefficient DT and dwell time TD. For the barrier height φ1=2.6 eV and φ2 = 1.4 eV, the width d=22 A and ExL = 1.0 eV, DT and TD have a maximum of 0.054 and 0.58x10^-15 s at V = 2.04 V and 2.18 V, respectively. This suggests that a real tunneling may be a hybrid.
基金supported by the National Natural Science Foundation of China(21476125)Tsinghua University Foundation(2013108930)State Key Laboratory of Chemical Engineering(SKL-CHE-10A01)
文摘While the preferential movement of water inside carbon nanotube is appealing for water purification,our understanding of the water transport mechanism through carbon nanotube(CNT)-based membrane is far from adequate. Here we conducted molecular dynamics simulations to study how the alignment of the CNTs in the membrane affects the water transport through the CNT membrane. It was shown that compared to the conventional CNT membrane where the alignment of CNTs was vertical to membrane surface, the ‘‘italicized CNT membrane'' in which the contact angel between membrane surface and the CNT alignment is not 90° offered a higher transmembrane flux of water. The expanded exposure of more carbon atoms to water molecules reduced the energy barrier near the entrance of this italicized CNT membrane, compared to the vertical one. For water flows through the italicized CNT membrane, the Lennard-Jones interaction between water and nanotube as function of central path of the CNT changes from ‘‘U'' to ‘‘V'' pattern, which significantly lowers energy barrier for filling water into the CNT,favoring the water transport inside carbon nanotube. Above simulation indicates new opportunities for applying CNT in water purification or related fields in which water transport matters.
基金supported by the National Key Basic Research and Development Program of China (2009CB623604)the National Natural Science Foundation of China (50990060, 51073809 and 21161160447)
文摘The hole and electron mobilities of the amorphous films of the organic semiconductor 4,4′-N,N′-dicarbazole-biphenyl (CBP) at different electric fields were measured through the time of flight (TOF) method. Based on its crystalline structure, the hole and electron mobilities of CBP were calculated. A detailed comparison between experimental and theoretical results is necessary for further understanding its charge transport properties. In order to do this, charge mobilities at zero electric field, μ(0), were deduced from experimental data as a link between experimental and theoretical data. It was found that the electron transport of CBP is less affected by traps compared with its hole transport. This unusual phenomenon can be understood through the distributions of frontier molecular orbitals. We showed that designing materials with frontier molecular orbitals localized at the center of the molecule has the potency to reduce the influence of traps on charge transport and provide new insights into designing high mobility charge transport materials.
文摘The mechanism of heat transfer enhancement by liquid film on the channel walls has been investigated in laminar mixed convective flows. The temperature distribution, velocity and mass fraction distributions, and the effects of the wetted wall temperatures and the Reynolds number on the momentum,heat and mass transfer were examined in details. Results show that the liquid film can enhance heat transfer along the wetted walls by 5-10 times.
基金supported by the National Key Research and Development Program of China(2016YFA0201001)National Natural Science Foundation of China(11627801,51102172)+3 种基金Science and Technology Plan of Shenzhen City(JCYJ20160331191436180)Natural Science Foundation for Outstanding Young Researcher in Hebei Province(E2016210093)the Key Program of Educational Commission of Hebei Province of China(ZD2016022)the Youth Top-notch Talents Supporting Plan of Hebei Province,Hebei Provincial Key Laboratory of Traffic Engineering materials and Hebei Key Discipline Construction Project
文摘Effective electron selective layer （ESL） is critical for the power conversion efficiency in organometal halide- based perovskite solar cells （PSCs）. In this work, a spincoating process has been developed to fabricate high quality nanocrystalline SnO2 film at 100℃ without further sintering at higher temperature. When used as ESL in PSCs, such SnO2 film shows greater electron extraction ability and higher efficiency than TiO2 film processed under similar condition, as evidenced by the efficient time-resolved photoluminescence （TRPL） quenching SnO2/CH3NH3PbI3 film. As a resuit, the SnO2-based PSCs possess higher open circuit voltage of 0.91 V, short circuit current density of 20.73 mA cm^-2, and fill factor of 64.25%, corresponding to a conversion efficiency of 12.10%, compared with 7.16% of TiO2-based PSCs. This demonstrates the great potential of applying spin-coating sintering-free process for the low-cost and large-scale manufacturing of PSCs.
基金supported by the National Natural Science Foundation of China(52073131,51902148,and 12047501)the Fundamental Research Funds for the Central Universities(lzujbky-2021-it31,lzujbky-2021-59,lzujbky-2021-ct15,lzujbky2021-ct01,and lzujbky-2021-sp69)supported by Supercomputing Center of Lanzhou University。
文摘Two-dimensional(2D)Dion-Jacobson(D-J)-type cesium lead iodide CsPbI_(3) perform remarkably in terms of stability.However,the complex interactions between spacer and inorganic layers limit its excellent progress in perovskite solar cells(PSCs).Herein,starting from the considerable structural diversity of organic spacers,we engineer 2D CsPbI_(3) with fine-tuning functionalities.Specifically,for the first time we embedded fluorinated aromatic cations in 2D D-J CsPbI_(3),and successfully applied it into construction of high-performance PSCs.Compared with constitutive 1,4-diaminobenzene(PDA),the fluorinated 2-fluorobenzene-1,4-diamine(F-PDA)component greatly expands the dipole moment from 0.59 D to 3.47 D,which reduces the exciton binding energy of the system.A theoretical study shows that the spacer layer and inorganic plane are more enriched with charge accumulation in(F-PDA)Csn±1 Pb_(n)I_(3n+1).The results show that(F-PDA)Csn±1Pb_(n)I_(3n+1) demonstrates more significant charge transfer between organic and inorganic layers than(PDA)Csn±1 Pb_(n)I_(3n+1),and it is confirmed in the femtosecond transient absorption experiment.Moreover,the interactions of the fluorinated spacer with the[PbI_(6)]_(4)-plane effectively manipulate the crystallization quality,and thus the ion migration and defect formation of target 2D CsPbI_(3) are inhibited.As a result,we obtained a record power conversion efficiency(PCE)beyond 15%for 2D D-J(F-PDA)Cs_(3)Pb_(4)I_(13)(n=4)PSCs with significantly improved environmental stability compared with the three-dimensional(3D)counterparts.
