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Oxygen-and photo-induced decay of perovskite solar cells:Mechanisms and strategies

Journal of Central South University 2024年第12期31卷 4366-4396页

作者： PENG Xin-xin ABDALLA Danyal LIU Fei DAOUD Walid A. YUAN Yong-bo LIN Yun Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China Department of Mechanical Engineering City University of Hong Kong83 Tat Chee AvenueHong KongChina

Perovskite solar cells(PSCs)have emerged as a promising photovoltaic technology with their rapid improvement in power conversion efficiency from 3.8%to 26.7%.However,the unsatisfactory stability is still a major hurdle to the future commercialization of *** various causes of instability,oxygen and photo-induced instability are indispensable aspects to be considered,especially there is a growing demand of manufacturing PSCs with low-cost environmental *** review aims to provide a timely and comprehensive summary of the investigations related to the oxygen-and photo-induced decay(OP-decay)in *** factors affecting the OP decay pathways and decay rate have been *** for the analysis of oxygen and photo-induced decay processes are *** for improving photo-oxygen stability have been summarized,from the aspects of suppressing the generation yield of superoxide,protecting perovskites from the generated superoxide,and slowing down the oxygen penetration,respectively.

关键词： perovskite solar cells oxygen-and photo-induced decay superoxide stability

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Precise quantum control of molecular rotation toward a desired orientation

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Physical Review Research 2025年第1期7卷 L012049-L012049页

作者： Qian-Qian Hong Daoyi Dong Niels E. Henriksen Franco Nori Jun He Chuan-Cun Shu Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Australian Artificial Intelligence Institute Faculty of Engineering and Information Technology University of Technology Sydney NSW 2007 Australia Department of Chemistry Technical University of Denmark Building 207 DK-2800 Kongens Lyngby Denmark Quantum Computing Center and Theoretical Quantum Physics Laboratory RIKEN Saitama 351-0198 Japan Physics Department University of Michigan Ann Arbor Michigan 48109 USA

The lack of a direct map between control fields and desired control objectives poses a significant challenge in applying quantum control theory to quantum technologies. Here, we propose an analytical framework to precisely control a limited set of quantum states and construct desired coherent superpositions using a well-designed laser pulse sequence with optimal amplitudes, phases, and delays. This theoretical framework that corresponds to a multilevel pulse-area theorem establishes a straightforward mapping between the control parameters of the pulse sequence and the amplitudes and phases of rotational states within a specific subspace. As an example, we utilize this approach to generate 15 distinct and desired rotational superpositions of ultracold polar molecules, leading to 15 desired field-free molecular orientations. By optimizing the superposition of the lowest 16 rotational states, we demonstrate that this approach can achieve a maximum orientation value of |〈cosθ〉|max above 0.99, which is very close to the global optimal value of 1 that could be achieved in an infinite-dimensional state space. This work marks a significant advancement in achieving precise control over multilevel subsystems within molecules. It holds potential applications in molecular alignment and orientation, as well as in various interdisciplinary fields related to the precise quantum control of ultracold polar molecules, opening up considerable opportunities in molecular-based quantum techniques.

关键词： Molecular orientation

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Electron Transport in Graphene Nanoribbons with Random ``5-5-8" Line Defects

SSRN

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SSRN 2024年

作者： Bhat, Irfan Hussain Hu, Pei-Jia Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China

This study investigates the electron transport properties of two-terminal disordered graphene nanoribbons (GNRs), considering the presence of randomly distributed ``5-5-8" line defects (LDs). Although the presence of random LDs causes significant localization and suppression in conductance, attributed to Anderson localization, several robust conductance peaks, including a quantized peak, can be observed in the transmission spectra of disordered GNRs regardless of sizes and LD concentrations. Furthermore, the study demonstrates that the width, particularly the edge configuration of disordered GNRs, significantly affects these peaks. In the case of symmetric edge configurations, the number of peaks remains constant, but their positions shift as the width increases. In contrast, for asymmetric edge configurations, the number and positions of the peaks change with width. Notably, a quantized conductance peak regardless of various configurations is observed. The study offer valuable insights for the design GNR devices based on LDs and edge symmetry. © 2024, The Authors. All rights reserved.

关键词： Graphene

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Maximizing orientation of a three-state molecule in a cavity with analytically designed pulses

arXiv

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arXiv 2024年

作者： Fan, Li-Bao Li, Hai-Ji Chen, Qi Zhou, Hang Liu, Heng Shu, Chuan-Cun Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China

We theoretically explore the precise control of a molecular polariton by strongly coupling the lowest three rotational states of a single molecule with a single-mode cavity. We examine two distinct cavity resonance configurations: a fundamental frequency cavity (ωc = 2B with the rotational constant B) resonating with the lowest two rotational states, and a second harmonic cavity (ωc = 4B) coupling with the first and second excited rotational states. We propose two control schemes based on the two polariton configurations and derive the corresponding pulse-area theorems to achieve a theoretical maximum orientation of 0.7746, identical to the molecule in the absence of the cavity. The control schemes are analyzed in Carbonyl Sulfide (OCS) molecules in their ground rotational state. Our numerical simulation results demonstrate the theoretical control schemes and analyze the sensitivity of the molecular polariton orientation degree to the control field bandwidth and phases. This work provides a valuable reference for achieving maximum field-free orientation of ultracold three-state molecules in a cavity using analytically designed pulses. Copyright © 2024, The Authors. All rights reserved.

关键词： Molecular polarity

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Interface engineering of FAPbI_(3) for passivating defects and improving stability with lead chalcogenides

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Journal of Central South University 2024年第12期31卷 4625-4637页

作者： LI Yun-hao FENG Xiang-xiang LONG Meng-qiu CAI Meng-qiu YANG Jun-liang LIU Biao Hunan Key Laboratory of Nanophotonics and Devices School of PhysicsCentral South UniversityChangsha 410083China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China School of Physics and Electronics Science Hunan UniversityChangsha 410082China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

Interface engineering is widely employed to enhance the performance of formamidinium lead triiodide(FAPbI_(3))perovskite solar *** this study,six different FAPbI_(3)/PbX(X=S,Se and Te)heterostructures are constructed,including the PbI interface and I interface *** addition,the lead vacancies(V-Pb)and iodine vacancies(V-I)are designed at the perovskite *** results show that the PbI interface is more stable than I interface in the *** PbX covering layer on the surface of the FAPbI_(3) perovskite stabilizes the perovskite octahedral structure by interface interactions and charge reconstruction that are beneficial to passivate perovskite interface defects and inhibit the phase *** shows that the PbTe covering layer exhibits the best passivation effect for lead vacancy defects,while PbS covering layer shows the best passivation effect for iodine vacancy ***,appropriate structural stress can strengthen the thermal stability of defective *** work reveals the FAPbI_(3)/PbX interface engineering,and offers new insights into effectively passivating defects and improving the stability of FAPbI_(3).

关键词： interface engineering FAPbI_(3) PbX PSCs stability

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Giant valley polarization and perpendicular magnetocrystalline anisotropy energy in monolayer MX2 (M=Ru,Os;X=Cl,Br)

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Physical Review B 2024年第2期109卷 024406-024406页

作者： Weifeng Xie Long Zhang Yunliang Yue Min Li Hui Wang School of Physics Hunan Key Laboratory of Super Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China College of Information Engineering Yangzhou University Yangzhou 225127 China

Large valley polarization and perpendicular magnetocrystalline anisotropy energy (PMAE) in room-temperature ferrovalley materials has been pursued for a long time because PMAE not only stabilizes long-range ferromagnetic (FM) order but also ensures spontaneous valley polarization. Herein, valley polarization and MAE of monolayer MX2 (M=Ru,Os; X=Cl,Br) are investigated based on first-principles calculations, Wannier functions, and Monte Carlo simulations. It is found that OsBr2 has a giant valley polarization of 327.158 meV and PMAE of 10.354 meV, ascribing to the strong spin-orbital coupling. The physical mechanism of valley polarization and PMAE are analyzed both qualitatively and quantitatively on the basis of perturbation theory, which shows that the valley polarization induces the distribution of MAE at K and K′ valley points with opposite signs, and the couplings between dz2 and dyz, dxz and dxy, and dx2−y2 and dyz in opposite spin channels through orbital angular momentum operator L̂x have a dominant contribution to the total MAE. Moreover, doping of a few holes and biaxial compressive strain both remarkably improve the PMAE of OsBr2. Meanwhile, the compressive strain can enhance FM exchange coupling of OsBr2, increasing the Curie temperature Tc far beyond the room temperature. Additionally, doping of a few electrons can significantly increase the PMAE of room-temperature ferrovalley OsCl2 to reach ∼40 meV. In this paper, we elucidate the physical mechanism of the valley polarization and MAE and indicate that monolayer OsCl2 and OsBr2 are promising for application in valleytronic and magnetic storage devices at room-temperature condition.

关键词： Magnetic anisotropy Spin-orbit coupling Valleytronics 2-dimensional systems Density functional calculations Monte Carlo methods

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Organic solar cells with D18 or derivatives offer efficiency over 19%

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Journal of Semiconductors 2024年第5期45卷 1-4页

作者： Erming Feng Chujun Zhang Jianhui Chang Hengyue Li Liming Ding Junliang Yang Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China Center for Excellence in Nanoscience Key Laboratory of Nanosystem and Hierarchical Fabrication(CAS)National Center for Nanoscience and TechnologyBeijing 100190China

In recent years,organic solar cells(OSCs)have garnered significant attention due to their distinctive attributes,such as flexibility,lightweight,and solution processing,which position them as alternatives for next-generation solar technologies[1−5].Thanks to breakthroughs in materials development,the power conversion efficiency(PCE)for single-junction OSCs has already surpassed 19%[6−13].The development of photoactive materials is pivotal in enhancing the PCEs,and several reviews have provided insights into materials design[14−18].Herein,we highlight single-junction OSCs based on D18 and its derivatives[19,20].

关键词： breakthrough insight derivatives

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Evidence for interlayer coupling and moiréexcitons in twisted WS_(2)/WS_(2)homostructure superlattices

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Nano Research 2023年第2期16卷 3429-3434页

作者： Haihong Zheng Biao Wu Shaofei Li Jun He Keqiu Chen Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China State Key Laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia The University of Sydney Nano Institute The University of SydneyNSW 2006Australia Shenzhen Research Institute of Central South University Shenzhen 518000China

The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)*** graphene and transition metal dichalcogenides(TMDs)moirésystems,twist angle has been shown to be a key parameter for regulating the moiré***,the effect of the modulation of the twist angle on moirépotential and interlayer coupling has not been the subject of experimental ***,we report the observation of the modulation of moirépotential and intralayer excitons in the WS_(2)/WS_(2)*** accurately adjusting the torsion angle of the homobilayers,the depth of the moirépotential can be *** confinement effect of the moirépotential on the intralayer excitons was further demonstrated by the changing of temperature and valley ***,we show that a detection of atomic reconstructions by the low-frequency Raman mapping to map out inhomogeneities in moirélattices on a large scale,which endows the uniformity of interlayer *** results provide insights for an in-depth understanding of the behaviors of moiréexcitons in the twisted van der Waals homostructure,and promote the study of electrical engineering and topological photonics.

关键词： moirésuperlattices moiréexcitons interlayer coupling moirépotential

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Maximizing orientation of a three-state molecule in a cavity with analytically designed pulses

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Physical Review A 2025年第3期111卷 033119-033119页

作者： Li-Bao Fan Hai-Ji Li Qi Chen Hang Zhou Heng Liu Chuan-Cun Shu Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering School of Physics and Electronic Science Changsha University of Science and Technology Changsha 410114 China

We theoretically explore the precise control of a molecular polariton by strongly coupling the lowest three rotational states of a single molecule with a single-mode cavity. We examine two distinct cavity resonance configurations: a fundamental frequency cavity (ωc=2B with the rotational constant B) resonating with the lowest two rotational states, and a second harmonic cavity (ωc=4B) coupling with the first and second excited rotational states. We propose two control schemes based on the two polariton configurations and derive the corresponding pulse-area theorems to achieve a theoretical maximum orientation of 0.7746, identical to the molecule without the cavity. The control schemes are analyzed in carbonyl sulfide (OCS) molecules in their ground rotational state. Our numerical simulation results demonstrate the theoretical control schemes and analyze the sensitivity of the molecular polariton orientation degree to the control field bandwidth and phases. This work provides a valuable reference for achieving maximum field-free orientation of ultracold three-state molecules in a cavity using analytically designed pulses.

关键词： Molecular polarity

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Observation of interlayer excitons in trilayer type-Ⅱ transition metal dichalcogenide heterostructures

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Nano Research 2022年第10期15卷 9588-9594页

作者： Biao Wu Haihong Zheng Junnan Ding Yunpeng Wang Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China State Key Laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia Shenzhen Research Institute of Central South University Shenzhen 518057China

Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional *** such structures,spatially indirect interlayer excitons(IXs)can be generated in adjacent layers because of strong Coulomb ***,due to the complexity of the multilayered heterostructure(HS),the capture and study of the IXs in trilayer type-Ⅱ HSs have so far remained ***,we present the observation of the IXs in trilayer type-Ⅱ staggered band alignment of MoS_(2)/MoSe_(2)/WSe_(2) van der Waals(vdW)HSs by photoluminescence(PL)*** central energy of IX is 1.33 eV,and the energy difference between the extracted double peaks is 23 *** confirmed the origin of IX through PL properties and calculations by the density functional theory,we also studied the dependence of the IX emission peak on laser power and ***,the polarization-resolved PL spectra of HS were also investigated,and the maximum polarizability of the emission peak of WSe_(2) reached 11.40%at 6 *** findings offer opportunities for the study of new physical properties of excitons in TMD HSs and therefore are valuable for exploring the potential applications of TMDs in optoelectronic devices.

关键词： transition metal dichalcogenides interlayer exciton type-II band alignment trilayer heterostructure

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