How does graphene enhance the photoelectric conversion efficiency of dye sensitized solar cells? An insight from a theoretical perspective
作者：
Xi, Jian-Ying;Jia, Ran* ;Li, Wei;Wang, Jian;Bai, Fu-Quan;...
期刊：
Journal of Materials Chemistry A ,2019年7(6):2730-2740 ISSN：2050-7488
通讯作者：
Jia, Ran;Zhang, Hong-Xing
作者机构：
[Wang, Jian; Jia, Ran; Zhang, Hong-Xing; Xi, Jian-Ying; Bai, Fu-Quan] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Peoples R China.;[Eglitis, Roberts I.; Jia, Ran] Univ Latvia, Inst Solid State Phys, 8 Kengaraga Str, LV-1067 Riga, Latvia.;[Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
通讯机构：
[Jia, R; Zhang, HX] J;[Jia, Ran] U;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Peoples R China.;Univ Latvia, Inst Solid State Phys, 8 Kengaraga Str, LV-1067 Riga, Latvia.
摘要：
The main goal of this work is to clearly answer the question from a theoretical perspective: how does graphene enhance the photoelectric conversion efficiency in the semiconducting layer of a dye sensitized solar cell? Several arrangements of the graphene layer between the dye molecule and the TiO 2 (101) surface are carefully studied and discussed. The dynamic interfacial electron propagations are simulated with consideration of the underlying nuclear motion effect. Theoretical investigation shows that graphene can speed up the electron injection from the dye molecules to the semiconductor layer, only when the graphene sheet is bonded to the TiO 2 surface via C-Ti bonds. The excited electrons of the dye molecules on the graphene sheet will be rapidly injected into the semiconducting layer. Additionally, if the graphene sheet is parallel to the TiO 2 surface, the free electrons on graphene can only hop onto the TiO 2 surface in a relatively long tunneling period. Therefore, graphene in this case mainly plays the role of a shielding layer for preventing the recombination of the electrons injected into TiO 2 and the electron holes remaining on the dye molecules or in the electrolyte. The combination of these two mechanisms indicates that graphene layers in the proper conformation can effectively improve the photoelectric conversion efficiency of a dye sensitized solar cell. © 2019 The Royal Society of Chemistry.
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英文
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Unraveling photoexcitation dynamics at "dots-in-a-perovskite" heterojunctions from first-principles
作者：
Li, Wei;Zhang, Xu;Lu, Gang*
期刊：
Journal of Materials Chemistry A ,2019年7(30):18012-18019 ISSN：2050-7488
通讯作者：
Lu, Gang
作者机构：
[Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Zhang, Xu; Lu, Gang] Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA.
通讯机构：
[Lu, Gang] C;Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA.
摘要：
Both organohalide perovskites and colloidal quantum dots are attractive and promising materials for optoelectronic applications. Recent experiments have combined the two to create "quantum dot-in-perovskite" assemblies for highly efficient light emissions. In this work, we unravel photoexcitation dynamics at the interface between the perovskite and the quantum dot by means of first-principles non-adiabatic molecular dynamics simulations. We find that such assemblies adopt the type-I band structure and are free of defect states. The interfacial and the electronic structure are robust against the thermal fluctuations at 300 K. The lowest excitation is predicted to be localized entirely on the quantum dot and the photoexcited charge transfer takes place in a picosecond timescale. The charge transfer dynamics of the photoexcited electron and hole exhibits a moderate asymmetry, which can be attributed to the differences in electronic coupling between the donor and the acceptor. The ultrafast and balanced charge transfer dynamics endows the 'dot-in-a-crystal' devices with unprecedented performance, which could lead to important applications in photovoltaics, photocatalysis, and infrared light emissions. © 2019 The Royal Society of Chemistry.
语种：
英文
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Theoretical design of porphyrin dyes with electron-deficit heterocycles towards near-IR light sensitization in dye-sensitized solar cells
作者：
Li, Wei;Ren, Wenhui;Chen, Zhi;Lu, Teng-Fei* ;Deng, Lei;...
期刊：
Taiyo Enerugi ,2019年188:742-749 ISSN：0038-092X
通讯作者：
Zhang, Xingming;Wang, Liang;Lu, Teng-Fei
作者机构：
[Chen, Zhi; Deng, Lei; Zhang, XM; Wang, Liang; Tang, Jianfeng; Li, Wei; Ren, Wenhui; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Bai, Fu-Quan; Lu, Teng-Fei] Jilin Univ, Inst Theoret Chem, Int Joint Res Lab Nanomicro Architecture Chem, Changchun 130023, Jilin, Peoples R China.
通讯机构：
[Zhang, XM; Wang, L] H;[Lu, Teng-Fei] J;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Jilin Univ, Inst Theoret Chem, Int Joint Res Lab Nanomicro Architecture Chem, Changchun 130023, Jilin, Peoples R China.
关键词：
Absorption spectrum;Charge transfer;Density functional theory;Dye-sensitized solar cells;Electronic structure
摘要：
We develop a series of porphyrin sensitizers with electron-deficit heterocycles based on the well-known YD2-o-C8 dye for application in dye-sensitized solar cells with the help of ab initio density functional theory calculations and quantum dynamics simulation based on the tight-binding extended Hückel Hamiltonian at the semiempirical level. The calculation results show that introduction of electron-deficit heterocycles into the porphyrin dyes can remarkably red-shift and broaden the Q band of the absorption spectrum and extend the coverage into near-infrared region, improving the light-harvesting ability. The key parameters influencing the photocurrent and photovoltage performance such as maximum short-circuit photocurrent (JSC max), intramolecular charge transfer, interface electron injection, and the shift of TiO2 conduction band edge (ΔECB) are superior to YD2-o-C8 dye. Therefore, the designed sensitizers would be promising candidate for utilization in dye-sensitized solar cells. © 2019 International Solar Energy Society
语种：
英文
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Theoretical investigations of the aromaticity, stability and photophysical behaviors for expanded porphyrins
作者：
Wei, Wei;Li, Wei;Xia, Bao-Hui* ;Zhang, Hong-Xing;Bai, Fu-Quan*
期刊：
Chemical Physics Letters ,2019年728:25-31 ISSN：0009-2614
通讯作者：
Xia, Bao-Hui;Bai, Fu-Quan
作者机构：
[Xia, Bao-Hui; Bai, Fu-Quan; Wei, Wei; Zhang, Hong-Xing] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130012, Jilin, Peoples R China.;[Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Xia, Bao-Hui] Jilin Univ, Coll Chem, Changchun 130023, Jilin, Peoples R China.
通讯机构：
[Xia, BH; Bai, FQ; Xia, Bao-Hui] J;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130012, Jilin, Peoples R China.;Jilin Univ, Coll Chem, Changchun 130023, Jilin, Peoples R China.
关键词：
Aromaticity;DFT;Expanded porphyrins;Photophysical behaviors;Stability
摘要：
We design a series of expanded porphyrins which are incorporated of dithienothiophene (DTT), 2,2′-bithiophene, inverted thiophene ring or selenophene ring and substituted of the pyrrole NH groups by S and Se heteroatoms. The molecule with 2,2′-bithiophene is more stable than the molecule with DTT. The expanded porphyrins with a thiophene or selenophene ring are more stable than the expanded porphyrins with an inverted thiophene or inverted selenophene ring. 6 shows special features due to its increased HOMO-LUMO gap, planar geometry, and strengthened aromaticity. We expect that this work can provide help to design and synthesize stable molecular materials. © 2019 Elsevier B.V.
语种：
英文
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Anharmonicity Extends Carrier Lifetimes in Lead Halide Perovskites at Elevated Temperatures.
作者：
Li, Wei;Vasenko, Andrey S.;Tang, Jianfeng* ;Prezhdo, Oleg V.*
期刊：
Journal of Physical Chemistry Letters ,2019年10(20):6219-6226 ISSN：1948-7185
通讯作者：
Tang, Jianfeng;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Vasenko, Andrey S.] Natl Res Univ Higher Sch Econ, Moscow 101000, Russia.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Tang, Jianfeng] H;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
关键词：
Carrier lifetime;Density functional theory;Energy harvesting;Lead compounds;Molecular dynamics;organic-inorganic materials;Photocatalytic activity;Solar energy;Temperature distribution;Electron-hole recombination;Electronic subsystems;Equilibrium geometries;Hybrid organic-inorganic;In-depth understanding;Nonadiabatic molecular dynamics;Optoelectronic applications;Temperature dependence;Perovskite
摘要：
Lead halide perovskites constitute a very promising class of materials for a broad range of solar and optoelectronic applications. Perovskites exhibit many unusual properties, and recent experiments demonstrate an unusual temperature dependence of charge carrier lifetimes. Focusing on the all-inorganic CsPbBr3, and using a combination of ab initio nonadiabatic molecular dynamics and time-domain density functional theory, we demonstrate that the unconventional behavior arises because of a highly anharmonic nature of atomic motions in perovskites. As temperature increases, perovskite structure undergoes a notable deformation, reflected in tilting of octahedral units, and experiences large-scale anharmonic movements away from the equilibrium geometry. As a result, the electronic energy gap increases, and phonon-induced loss of coherence within the electronic subsystem accelerates. These two factors slow down nonradiative electron-hole recombination, which constitutes the main limitation on efficiencies of perovskite solar, optical, and electronic devices. The increase of charge carrier lifetimes with temperature is particularly beneficial in applications, because materials heat up, for instance, from sunlight during solar energy harvesting. The behavior of the all-inorganic halide perovskite investigated here is different from that of hybrid organic-inorganic perovskites, which exhibit additional disorder associated with reorientations of the asymmetric organic cations. The reported simulations generate an in-depth understanding of the unusual properties of inorganic perovskites, relevant for photocatalytic, photovoltaic, electronic, and optical applications. © 2019 American Chemical Society.
语种：
英文
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Theoretical study on organic dyes with tunable π-spacers for dye-sensitized solar cells: Inspired by the organic polymer photovoltaics
作者：
Xie, Xiaoyin;Liu, Zhihai;Li, Wei;Bai, Fu-Quan* ;Lee, Eun-Cheol* ;...
期刊：
Chemical Physics Letters ,2019年719:39-44 ISSN：0009-2614
通讯作者：
Bai, Fu-Quan;Zhang, Hong-Xing;Lee, Eun-Cheol
作者机构：
[Bai, Fu-Quan; Zhang, Hong-Xing; Xie, Xiaoyin; Zhang, HX] Jilin Univ, Inst Theoret Chem, Int Joint Res Lab Nanomicro Architecture Chem, Changchun 130023, Jilin, Peoples R China.;[Xie, Xiaoyin] Jilin Inst Chem Technol, Dept Chem Technol, Jilin 132022, Jilin, Peoples R China.;[Liu, Zhihai] Yantai Univ, Sch Optoelect Informat Sci & Technol, Yantai 264005, Shandong, Peoples R China.;[Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Lee, Eun-Cheol] Gachon Univ, Dept Nanophys, Gyeonggi 13120, South Korea.
通讯机构：
[Bai, FQ; Zhang, HX] J;[Lee, Eun-Cheol] G;Jilin Univ, Inst Theoret Chem, Int Joint Res Lab Nanomicro Architecture Chem, Changchun 130023, Jilin, Peoples R China.;Gachon Univ, Dept Nanophys, Gyeonggi 13120, South Korea.
关键词：
Dye-sensitized solar cells;Organic dyes;Polymer photovoltaics;Theoretical investigation;π-spacer
摘要：
We present the theoretical investigation on tuning π-spacers in D-π-A organic dyes for dye-sensitized solar cells (DSSCs). The validity of three series of conjugate units (12 types) conventionally used in polymer photovoltaics are utilized as the π-spacers of organic dyes. Our results indicate that the extension of π conjugation can efficiently improve the absorption intensity. The absorption spectra red-shifts is because the increased π-spacers significantly destabilize the highest occupied molecular orbital level, whereas the lowest unoccupied molecular orbital level has negligible changed. Our simulation is expected to assist the design high performance dyes for dye-sensitized solar cells applications. © 2019 Elsevier B.V.
语种：
英文
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Intrinsic strain-induced segregation in multiply twinned Cu-Pt icosahedra
作者：
Deng, Lei;Liu, Xunlin;Zhang, Xingming* ;Wang, Liang;Li, Wei;...
期刊：
PHYSICAL CHEMISTRY CHEMICAL PHYSICS ,2019年21(9):4802-4809 ISSN：1463-9076
通讯作者：
Zhang, Xingming;Tang, Jianfeng
作者机构：
[Zhang, XM; Tang, Jianfeng; Deng, Lei; Li, Wei; Liu, Xunlin; Wang, Liang; Song, Mingke; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, Huiqiu; Hu, Wangyu] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.;[Xiao, Shifang] Hunan Univ, Sch Phys & Elect, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, XM; Tang, JF] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
摘要：
We present an atomistic simulation study on the compositional arrangements throughout Cu-Pt icosahedra, with a specific focus on the effects of inherent strain on general segregation trends. The coexistence of radial and site-selective segregation patterns is found in bimetallic nanoparticles for a broad range of sizes and compositions, consistent with prior analytical and atomistic models. Through a thorough comparison between the composition patterns and strain-related patterns, it is suggested that the presence of gradient and site-selective segregation is natural to largely relieve the inherent strain by preferential segregation of big atoms at tensile sites and vice versa, as previously hypothesized in the literature. Analogous to the case of single crystal particles, Cu-rich surface and damped oscillations can also be found in the outer shells of icosahedra, which are dominated by the lowering of both the surface energy and the chemical energy. The thermodynamic stability of segregated icosahedra is similar to segregated cuboctahedra but higher than disordered bulk alloys, validating prior thinking that element segregation driven by strain relief can extend the stability range of multiply-twinned nanoparticles. Our work sheds new light on understanding strain-induced segregation in multiply-twinned nanosystems that have elements with large lattice mismatch and strong alloying ability. © the Owner Societies.
语种：
英文
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Precipitate/vanadium interface and its strengthening on the vanadium alloys: A first-principles study
作者：
Zhang, Xingming;Li, Yifang;Tang, Jianfeng;Deng, Lei;Li, Wei;...
期刊：
Journal of Nuclear Materials ,2019年527:151821 ISSN：0022-3115
通讯作者：
Wang, Liang
作者机构：
[Deng, Lei; Li, Yifang; Tang, Jianfeng; Li, Wei; Wang, Liang; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, Huiqiu] Hunan Univ, Sch Phys & Elect, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China.;[Hu, Wangyu] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Wang, Liang] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
关键词：
Calculations;Density functional theory;Stress-strain curves;Tensile strain;Tensile strength;Vanadium alloys;First principles;First-principles calculation;First-principles study;Ideal tensile strengths;Orientation relationship;Precipitation strengthening;Solute;Uniaxial tensile loading;Precipitation (chemical)
摘要：
The precipitates of second phases with coherent or incoherent interfaces can interact with dislocations to act as slip obstacles that can significantly improve the mechanics properties of alloys. In this work, the first-principles calculations based on density functional theory were performed to characterize the precipitate/Vanadium interface in the vanadium alloys and uncovering how structure of precipitations and interfacial defects (vacancy or solutes) distribution influence on the effectiveness of precipitation strengthening. Based the Baker-Nutting orientation relationship, the equilibrium stable precipitate/matrix interface structure are obtained. It is found that the so-called layer buckling exists in the interfacial region. Meanwhile, considering the equilibrium interface structure, the compressive strain is taken up by the Ti-based precipitation in the interface. For V-based precipitations, on the contrary, the interfacial strain is reversed that the tensile strain is taken up by the V-based precipitations. Under the uniaxial tensile loading, the stress-strain relations of heterostructures with different kinds of precipitates MX (M = Ti, V and X = C, N) are obtained to characterize the precipitation strengthening in the Vanadium alloys. The ideal tensile strength for heterostructure is sensitive to the size of precipitation. Furthermore, it is interesting to note that Ti-based precipitations not only improve the tensile strength, but also meliorate the ductility of the V alloys, which pointing to the inference that Ti-based precipitations are more effective to strengthen the V alloys than V-based precipitations. Our findings from this study can be implemented into providing the theoretical strategy for further design of the new style alloys. © 2019 Elsevier B.V.
语种：
英文
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考虑损失规避与利他性的零售商的订购决策
作者：
李维
期刊：
经济研究导刊 ,2019年(3):58-60 ISSN：1673-291X
作者机构：
湖南农业大学 理学院,长沙,411000;[李维] 湖南农业大学
关键词：
损失规避;利他性;库存;定价;紧急订购
摘要：
在允许紧急订购的报童模型中,研究利他主义且损失规避的零售商面对损失中性供货商的订购决策。将利他性与损失规避联合考虑,建立模型并进行模型分析,得到最优订购量的隐函数方程,并分析损失规避系数、订购成本、零售价格、净残值以及紧急订购成本对最优定购量的影响,并对其进行数值分析,这对现实具有一定的指导意义。
语种：
中文
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Influence of Defects on Excited-State Dynamics in Lead Halide Perovskites: Time-Domain ab Initio Studies
作者：
Li, Wei* ;Long, Run* ;Tang, Jianfeng* ;Prezhdo, Oleg V.*
期刊：
Journal of Physical Chemistry Letters ,2019年10(13):3788-3804 ISSN：1948-7185
通讯作者：
Li, Wei;Tang, Jianfeng;Long, Run;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei; Li, W] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Long, Run] Beijing Normal Univ, Minist Educ, Key Lab Theoret & Computat Photochem, Coll Chem, Beijing 100875, Peoples R China.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Li, W; Tang, JF] H;[Long, Run] B;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Beijing Normal Univ, Minist Educ, Key Lab Theoret & Computat Photochem, Coll Chem, Beijing 100875, Peoples R China.
关键词：
Density functional theory;Energy dissipation;Grain boundaries;Laser spectroscopy;Lead compounds;Molecular dynamics;Perovskite;Perovskite solar cells;Point defects;Quantum theory;Ab initio density functional theories (DFT);Ab initio simulations;Excited-state dynamics;Halide perovskites;Nonadiabatic molecular dynamics;Photocatalytic application;Recent researches;Time-resolved spectroscopy;Excited states
摘要：
This Perspective summarizes recent research into the excited-state dynamics in lead halide perovskites that are of paramount importance for photovoltaic and photocatalytic applications. Nonadiabatic molecular dynamics combined with time-domain ab initio density functional theory allows one to mimic time-resolved spectroscopy experiments at the atomistic level of detail. The focus is placed on realistic aspects of perovskite materials, including point defects, surfaces, grain boundaries, mixed stoichiometries, dopants, and interfaces. The atomistic description of the quantum dynamics of electron and hole trapping and recombination, provided by the time-domain ab initio simulations, generates important insights into the mechanisms of charge and energy losses and guides the development of high-performance perovskite solar cell devices. © 2019 American Chemical Society.
语种：
英文
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Highly Active Co-Based Catalyst in Nanofiber Matrix as Advanced Sensing Layer for High Selectivity of Flexible Sensing Device
作者：
Wang, Kang;Li, Jing;Li, Wei;Wei, Wei;Zhang, Hao;...
期刊：
Advanced Materials Technologies ,2019年4(2):1800521- ISSN：2365-709X
通讯作者：
Wang, Lili
作者机构：
[Wang, Lili; Wang, Kang] Jilin Univ, State Key Lab Integrated Optoelect, Coll Elect Sci & Engn, Changchun 130012, Jilin, Peoples R China.;[Li, Jing] Jilin Univ, Hosp 1, Ctr Cardiovasc Dis, Changchun 130021, Peoples R China.;[Li, Wei] Hunan Agr Univ, Coll Sci, Changcha 410128, Peoples R China.;[Wei, Wei] Jilin Univ, Lab Theoret & Computat Chem, Inst Theoret Chem, Changchun 130012, Jilin, Peoples R China.;[Zhang, Hao] Shenzhen Technol Univ, Coll Hlth & Environm Engn, Shenzhen 518118, Peoples R China.
通讯机构：
[Wang, Lili] J;Jilin Univ, State Key Lab Integrated Optoelect, Coll Elect Sci & Engn, Changchun 130012, Jilin, Peoples R China.
关键词：
1D heteronanofibers;density functional theory;flexible sensing devices;high active facets;high selective sensitivity
摘要：
An efficient and economic sensing material for flexible chemical sensors is increasingly in great demand as a result of its potential application in the healthcare and environmental detection systems. Endowing the nanomaterials with high active facets serves as a promising method for the design of nanomaterials with advanced functionalities. New physicochemical properties of chemical sensor can be obtained by using high active facets nanoparticles combined in one-dimensional (1D) nanofiber/wires. However, it remains a great challenge to conduct the development of 1D heterostructure sensing materials with high selectivity, in particular the ones that can perform under room temperature. Here, a high performance flexible sensing device based on Co3O4 nanoparticles with specific (112) facet in α-Fe2O3 nanofiber is reported. The heterointerfaces and grain boundary allow the fast electrons transportation in sensing reactions and the (112) facets in Co3O4 nanoparticles provide a large number of highly active sites where the selective absorption of ammonia gas molecules occurs. Consequently, the flexible gas sensor exhibits ultrahigh sensitivity (417%) and mechanical stability to ammonia gas molecules, which are proved by using density functional theory calculations. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
语种：
英文
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Spin-Orbit Interactions Greatly Accelerate Nonradiative Dynamics in Lead Halide Perovskites
作者：
Li, Wei;Zhou, Liujiang;Prezhdo, Oleg, V* ;Akimov, Alexey, V*
期刊：
ACS Energy Letters ,2018年3(9):2159-2166 ISSN：2380-8195
通讯作者：
Prezhdo, Oleg, V;Akimov, Alexey, V
作者机构：
[Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Zhou, Liujiang] Los Alamos Natl Lab, Los Alamos, NM 87545 USA.;[Prezhdo, Oleg, V] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.;[Akimov, Alexey, V] Univ Buffalo State Univ New York, Dept Chem, Buffalo, NY 14260 USA.
通讯机构：
[Prezhdo, Oleg, V; Akimov, Alexey, V] U;Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.;Univ Buffalo State Univ New York, Dept Chem, Buffalo, NY 14260 USA.
摘要：
In this work, we study the role of spin-orbit coupling (SOC) in nonradiative relaxation of hot electrons and holes in methylammonium lead perovskite, MAPbI3. For this purpose, we have developed the nonadiabatic molecular dynamics method with two-component spinor wave functions that are solutions of the relativistic Kohn-Sham (KS) equations. We find that SOC enhances contributions of Pb(px) and Pb(py) orbitals to the conduction and valence bands. As a result, the KS orbitals become more sensitive to nuclear motions, leading to the increased nonadiabatic couplings. Consequently, SOC greatly speeds up the electron and hole relaxation, making the computed relaxation time scales consistent with available experiments. We suggest that the fast hot carrier relaxation facilitated by the SOC allows rapid transition into the long-lived triplet state that extends charge-carrier lifetime and helps achieve high-efficiency perovskite solar cells. © 2018 American Chemical Society.
语种：
英文
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Promising pyridinium ylide based anchors towards high-efficiency dyes for dye-sensitized solar cells applications: Insights from theoretical investigations
作者：
Lu, Teng-Fei;Li, Wei* ;Chen, Jie;Tang, Jianfeng;Bai, Fu-Quan;...
期刊：
Electrochimica Acta ,2018年283:1798-1805 ISSN：0013-4686
通讯作者：
Zhang, Hong-Xing;Li, Wei
作者机构：
[Bai, Fu-Quan; Lu, Teng-Fei; Zhang, Hong-Xing; Chen, Jie] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.;[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
通讯机构：
[Zhang, Hong-Xing] J;[Li, Wei] H;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
关键词：
Dye-sensitized solar cell;Density function theory;Charge transfer;Anchoring group;Organic dye
摘要：
We theoretically examine a series of anchors for dye-sensitized solar cells application, with particular attention was paid to the potential of novel pyridinium ylide based anchors. The geometrical structure, electronic property, and optical spectrum of the isolated dyes and its interface with TiO2 are analyzed by using quantum chemistry calculations. Quantum dynamics simulation is performed to investigate the interface electron transfer process across the dye/TiO2 interface. The key parameters influencing the short-circuit current and open-circuit voltage are calculated to quantify the performance of different dyes. Our results show that the pyridinium ylide based anchors benefit light-harvesting and improve intramolecular charge transfer character as well as shift up the conduction band edge of TiO2 semiconductor which further increase short-circuit current and open-circuit voltage. Conjugated rhodanime-3-acetic anchor exhibits the enhanced electron injection than the non-conjugated structure due to the more significant donor-acceptor interaction. The simulation performed in this work demonstrates the potential of novel pyridinium ylide based anchors with respect to the traditional carboxylic acid and rhodanime-3-acetic based anchors, reveals the crucial role of local structure variation in the interface electron transfer, and finally guides the design of high-efficiency sensitizer for dye-sensitized solar cells application.
We theoretically examine a series of anchors for dye-sensitized solar cells application, with particular attention was paid to the potential of novel pyridinium ylide based anchors. The geometrical structure, electronic property, and optical spectrum of the isolated dyes and its interface with TiO2 are analyzed by using quantum chemistry calculations. Quantum dynamics simulation is performed to investigate the interface electron transfer process across the dye/TiO2 interface. The key parameters influencing the short-circuit current and open-circuit voltage are calculated to quantify the performance of different dyes. Our results show that the pyridinium ylide based anchors benefit light-harvesting and improve intramolecular charge transfer character as well as shift up the conduction band edge of TiO2 semiconductor which further increase short-circuit current and open-circuit voltage. Conjugated rhodanime-3-acetic anchor exhibits the enhanced electron injection than the non-conjugated structure due to the more significant donor-acceptor interaction. The simulation performed in this work demonstrates the potential of novel pyridinium ylide based anchors with respect to the traditional carboxylic acid and rhodanime-3-acetic based anchors, reveals the crucial role of local structure variation in the interface electron transfer, and finally guides the design of high-efficiency sensitizer for dye-sensitized solar cells application.
语种：
英文
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Shock wave propagation, plasticity, and void collapse in open-cell nanoporous Ta
作者：
Tang, J. F.;Xiao, J. C.;Deng, L.;Li, W.;Zhang, X. M.* ;...
期刊：
PHYSICAL CHEMISTRY CHEMICAL PHYSICS ,2018年20(44):28039-28048 ISSN：1463-9076
通讯作者：
Zhang, X. M.;Wang, L.
作者机构：
[Li, W.; Zhang, XM; Wang, L.; Xiao, J. C.; Zhang, X. M.; Deng, L.; Tang, J. F.] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, H. Q.; Xiao, S. F.] Hunan Univ, Coll Phys & Micro Elect, Changsha 410082, Hunan, Peoples R China.;[Hu, W. Y.] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, XM; Wang, L] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
摘要：
We systematically investigate the wave propagation, plasticity and void collapse, as well as the effects of porosity, specific surface area and impact velocity, in a set of open-cell nanoporous Ta, during shock compression, via performing large-scale non-equilibrium molecular dynamics simulations. The shock wave propagation presents an impedance, sensitive to porosity, but not to specific surface area. Such surprising phenomena are due to the similar sensitivities in density and stress variations to porosity or specific surface area. Upon impact, shock front shapes change from ramped to steep ones, with increasing porosity, specific surface area or impact velocity, owing to the transition from the heterogeneous to homogeneous plasticity along transverse directions. This transition of plasticity arises by (i) the strong impedance on large deformation bands as porosity increases; and (ii) the transition from deformation twinning to dislocation slips, and to amorphization, as the specific surface area or impact velocity increases. Shock-induced plasticity, including their nucleation, growth and interactions, also facilitates the collapse of voids.
语种：
英文
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Influence of an exciton-delocalizing ligand on the structural, electronic, and spectral features of the Cd33S33 quantum dot: insights from computational studies
作者：
Li, Wei* ;Lu, Teng-Fei;Ren, Wenhui;Deng, Lei;Zhang, Xingming;...
期刊：
Journal of Materials Chemistry C ,2018年6(32):8751-8761 ISSN：2050-7526
通讯作者：
Li, Wei;Tang, Jianfeng;Kuznetsov, Aleksey E.
作者机构：
[Deng, Lei; Tang, Jianfeng; Li, Wei; Wang, Liang; Ren, Wenhui; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Li, Wei; Lu, Teng-Fei] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Peoples R China.;[Kuznetsov, Aleksey E.] Univ Sao Paulo SP, Inst Quim, Ave Prof Lineu Prestes 748, BR-05508000 Sao Paulo, SP, Brazil.
通讯机构：
[Li, W; Tang, JF] H;[Li, Wei] J;[Kuznetsov, Aleksey E.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Peoples R China.
关键词：
Binding energy;Cadmium compounds;Charge transfer;Computation theory;Density functional theory;Energy gap;Excited states;Excitons;Ground state;Ligands;Nanocrystals;Optical properties;Solar cells;Computational studies;Electronic band gaps;Excited-state properties;Exciton delocalization;High-energy absorption;Quantum dot transition;Theoretical investigations;Time dependent density functional theory;Semiconductor quantum dots
摘要：
Quantum dot based solar cells have attracted considerable attention owing to the unique geometrical, electronic, and optical properties of quantum dots. Exciton-delocalizing ligands, such as phenyldithiocarbamate, are demonstrated to benefit charge extraction in quantum dot-based solar cells. However, sufficient details of the exciton delocalization mechanism are still lacking. This work reports theoretical investigations concerning the role of the exciton-delocalizing linker for the ground- and excited-state properties of the Cd33S33 quantum dot. We perform density functional theory and time-dependent density functional theory investigations of the Cd33S33 quantum dot functionalized with two hole acceptors: PTC-PTZ, a phenothiazine ligand with the exciton-delocalizing phenyldithiocarbamate linker, and BA-PTZ, phenyldithiocarbamate with the benzoate linker which is not an exciton-delocalizing ligand. Our calculation results find that PTC-PTZ has two binding modes: bidentate binding and flat binding modes, with the latter being more favorable. The phenyldithiocarbamate linker tends to delocalize the charge densities compared to benzoate. For all complexes, solvent increases electronic band gaps and makes quantum dot-to-quantum dot transitions dominate for the high-energy absorption band. Electron density differences between the excited state and the ground state suggest that the exciton-delocalizing PTC-PTZ molecule, especially the flat binding mode, would induce more significant charge transfer in the direction from the quantum dot to the dye. © The Royal Society of Chemistry.
语种：
英文
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Time-Domain ab lnitio Analysis Rationalizes the Unusual Temperature Dependence of Charge Carrier Relaxation in Lead Halide Perovskite
作者：
Li, Wei* ;Tang, Jianfeng;Casanova, David;Prezhdo, Oleg V.*
期刊：
ACS Energy Letters ,2018年3(11):2713-2720 ISSN：2380-8195
通讯作者：
Li, Wei;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Casanova, David] DIPC, Donostia San Sebastian 20018, Euskadi, Spain.;[Casanova, David] IKERBASQUE, Basque Fdn Sci, Bilbao 48013, Euskadi, Spain.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Li, Wei] H;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
摘要：
Increased charge carrier lifetimes at elevated temperatures constitute an intriguing and valuable feature of hybrid organic-inorganic perovskites that are subject to heating in solar energy applications. We rationalize this peculiar behavior at the atomistic level using real-Time time-dependent density functional theory and nonadiabatic molecular dynamics. Focusing on tetragonal MAPbI3, we demonstrate that temperature has different effects on the organic and inorganic subsystems and leads to subtle structural changes, decreasing nonradiative electron-hole recombination. First, charge-phonon interactions are decreased because the libration dynamics of the organic component at higher temperature reduces the oscillation amplitude of the Pb-I lattice that supports electrons and holes. Second, thermal disorder localizes wave functions, reducing the nonadiabatic charge-phonon coupling. Third, tilting of the inorganic octahedra increases the bandgap, extending charge carrier lifetime further. The detailed time-domain atomistic analysis of the uncommon dependence of charge recombination on temperature emphasizes the key role played by the organic cation, establishes important structure-property relationships, provides valuable insights into efficient performance of perovskite solar cells, and highlights factors required to maintain and improve such performance. © 2018 American Chemical Society.
语种：
英文
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Control of Charge Recombination in Perovskites by Oxidation State of Halide Vacancy
作者：
Li, Wei;Sun, Yi-Yang;Li, Linqiu;Zhou, Zhaohui;Tang, Jianfeng* ;...
期刊：
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY ,2018年140(46):15753-15763 ISSN：0002-7863
通讯作者：
Tang, Jianfeng;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Sun, Yi-Yang] Chinese Acad Sci, Shanghai Inst Ceram, State Key Lab High Performance Ceram & Superfine, Shanghai 201899, Peoples R China.;[Li, Linqiu; Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.;[Zhou, Zhaohui] Changan Univ, Sch Environm Sci & Engn, Chem Engn & Technol, Xian 710064, Shaanxi, Peoples R China.;[Zhou, Zhaohui] Changan Univ, Minist Educ, Key Lab Subsurface Hydrol & Ecol Effects Arid Reg, Xian 710064, Shaanxi, Peoples R China.
通讯机构：
[Tang, Jianfeng] H;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
摘要：
Advances in perovskite solar cells require development of means to control and eliminate the nonradiative charge recombination pathway. Using ab initio nonadiabatic molecular dynamics, we demonstrate that charge recombination in perovskites is extremely sensitive to the charge state of the halogen vacancy. A missing iodine anion in MAPbI(3) has almost no effect on charge losses. However, when the vacancy is reduced, the recombination is accelerated by up to 2 orders of magnitude. The acceleration occurs due to formation of a deep hole trap in the singly reduced vacancy, and both deep and shallow hole traps for the doubly reduced vacancy. The shallow hole involves a significant rearrangement of the Pb-I lattice, leading to a new chemical species: a Pb-Pb dimer bound by the vacancy charge, and under-coordinated iodine bonds. Hole trapping by the singly reduced iodide vacancy operates parallel to recombination of free electron and hole, accelerating charge losses by a factor of S. The doubly reduced vacancy acts by a sequential mechanism-free hole, to shallow trap, to deep trap, to free electron, and accelerates the recombination by a factor of 50. The study demonstrates that iodine anion vacancy can be beneficial to the performance, because it causes minor changes to the charge carrier lifetime, while increasing charge carrier concentration. However, the neutral iodine and iodine cation vacancies should be strongly avoided. The detailed insights into the charge carrier trapping and relaxation mechanisms provided by the simulation are essential for development of efficient photocatalytic, photovoltaic, optoelectronic and related devices.
语种：
英文
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Influence of Encapsulated Water on Luminescence Energy, Line Width, and Lifetime of Carbon Nanotubes: Time Domain Ab Initio Analysis
作者：
Li, Wei* ;Long, Run;Hou, Zhufeng;Tang, Jianfeng;Prezhdo, Oleg V.*
期刊：
Journal of Physical Chemistry Letters ,2018年9(14):4006-4013 ISSN：1948-7185
通讯作者：
Li, Wei;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Li, Wei] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.;[Long, Run] Beijing Normal Univ, Minist Educ, Coll Chem, Key Lab Theoret & Computat Photochem, Beijing 100875, Peoples R China.;[Hou, Zhufeng] NIMS, 1-2-1 Sengen, Tsukuba, Ibaraki 3050047, Japan.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Li, Wei] H;[Li, Wei] J;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.
关键词：
Defects;Density functional theory;Electron diffraction;Electron scattering;Electron-phonon interactions;Electronic properties;Excited states;Luminescence;Molecular dynamics;Molecules;Phonon scattering;Time domain analysis;Yarn;Electron phonon scattering;Excited state lifetimes;Linewidth broadening;Nonadiabatic molecular dynamics;Radial breathing mode;Time dependent density functional theory;Vibrational dynamics;Vibrational properties;Carbon nanotubes
摘要：
In a broad range of applications, carbon nanotubes (CNTs) are in direct contact with a condensed-phase environment that perturbs CNT properties. Experiments show that water molecules encapsulated inside of semiconducting CNTs reduce the electronic energy gap, enhance elastic and inelastic electron-phonon scattering, and shorten the excited-state lifetime. We rationalize the observed effects at the atomistic level using real-time time-dependent density functional theory combined with nonadiabatic molecular dynamics. Encapsulated water makes the nanotube more rigid, suppressing radial breathing modes while enhancing and slightly shifting the optical G-mode. Water screens Coulomb interactions and shifts charge carrier energies and wave functions. The screening, together with distortion of the CNT geometry and lifting of orbital degeneracy, produces a luminescence red shift. Enhanced elastic and inelastic electron-phonon scattering explains line width broadening and shortening of the excited-state lifetime. The influence of water on the CNT properties is similar to that of defects; however, in contrast to defects, water creates no new phonon modes or electronic states in the CNTs. The atomistic understanding of the influence of the condensed-phase environment on CNT optical, electronic, and vibrational properties, and electron-vibrational dynamics guides design of novel CNT-based materials. Copyright © 2018 American Chemical Society.
语种：
英文
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高校概率统计课程教学方法的探讨
作者：
李维
期刊：
内江科技 ,2017年38(9):84-85 ISSN：1006-1436
作者机构：
湖南农业大学理学院;[李维] 湖南农业大学
关键词：
专业课程;概率统计;教学方法;概率论与数理统计;高校;高等院校;教学经验;教学效果
摘要：
概率论与数理统计课程是高等院校农林类专业的一门必修课,概率统计课程的学习对学生后续专业课程的学习起到重要的作用。本文结合作者的实际教学经验,对概率统计课程的教学方法进行了浅显的探讨,并在实际教学加以应用收到了较好的教学效果。
语种：
中文
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基于偏最小二乘回归的民航客运量预测与分析
作者：
李维;肖红专
期刊：
Kexue Jishu Chuangxin ,2017年(26):45-46 ISSN：1673-1328
作者机构：
湖南农业大学理学院,湖南 长沙,410128;[李维; 肖红专] 湖南农业大学
关键词：
民航客运量;偏最小二乘回归模型;预测
摘要：
民航客运量预测与分析结果直接影响民航交通规划与管理,对各机场与航空公司是否能够把握行业发展的趋势,并及时制定市场竞争规划有着重要意义。本文采用偏最小二乘回归模型,对2016-2020年的民航客运量做出预测。根据民航客运量需求与经济发展、对外开放之间的关系,分析民航客运量的影响因素,为航空业的民航客运量预测与研究提供了参考,对有效增加民航客运需求具有着一定的参考价值。
语种：
中文
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