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Perovskite Solar Cells Stability Factors And Encapsulaiton For Performance Enhancement DAI Jiaqi, ZHANG Dong, WU Xiaoshan Progress in Physics    2024, 44 (1): 19-48.   DOI: 10.13725/j.cnki.pip.2024.01.003 Abstract （2047）      PDF （5083KB）（1064）       Perovskite solar cells, which are considered the third generation of new concept solar cells, are known for their high photoelectric conversion efficiency, low cost, and flexible processing advantages, and have been rapidly development in recent years. its photoelectric conversion efficiency is gradually comparable to that of silicon cells and has been close to the level required for industrial applications. However, the main problem with the industrial application of perovskite solar cells is their stability. Researchers need to solve the biggest problem of how to maintain high efficiency for a long time in perovskite solar cells. Encapsulation is currently being widely studied as a solution to the external stability issue of perovskite solar cells. A good encapsulation can not only solve the stability problem of the device but also ensure the safety of the device and extend the service life. The stability of perovskite solar cells and the conditions for testing it are briefly described in this paper. In the end, the various encapsulation structures, techniques, and materials for perovskite solar cells are explained. The continuous advancement of encapsulation research will lead researchers to optimize and solve existing problems, leading to the eventual industrialization of perovskite solar cells on a large scale.  Related Articles | Metrics

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Halide Perovskite Single Crystals and Photodetectors: Research Progress and Challenges  SUN Yue, HUANG Xiao-rui , HE Sheng-rong, XING Jun Progress in Physics    2024, 44 (5): 209-242.   DOI: 10.13725/j.cnki.pip.2024.05.001 Abstract （1416）      PDF （15745KB）（1386）       In recent years, metal halide perovskite materials have made great scientific progress in the field of light detection, photoelectric conversion, and light emission due to their excellent optical and electrical properties (such as high absorption coefficient, long carrier diffusion length, small exciton binding energy, high defect tolerance, and adjustable band gap, etc.), and low-cost solution preparation process. In recent decades, scientific research on the preparation and optimization of perovskite single crystals has been promoted driven by their advantages compared to polycrystalline perovskite films. These advantages include longer carrier lifetime, higher carrier mobility, longer diffusion length, and lower trap density. High-quality halide perovskite single crystals have been widely used in important applications such as photodetection. This review focuses on the recent advancements in photodetector technology using various forms and chemical compositions of halide perovskite single crystals, including single crystal bulks and single crystal thin films. Firstly, we systematically review the preparation and optimization progress of halide perovskite single crystals, with a focus on the latest progress in triple cations hybrid perovskite single crystals. After that, a comprehensive introduction was given to the research status of various types of photodetectors based on perovskite single crystals. Finally, the current challenges and future development prospects in the research field of halide perovskite single crystal photodetector are summarized in order to promote rapid progress and development in this field. Related Articles | Metrics

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Vortex state in a nematic triplet superconductor YANG Miao-miao, XIANG Ke, WANG Da, WANG Qiang-hua Progress in Physics    2023, 43 (5): 131-141.   DOI: 10.13725/j.cnki.pip.2023.05.001 Abstract （1403）      PDF （452KB）（559）       The discovery of nematic triplet superconductivity in doped topological insulators CuxBi2Se3 triggers interest in the identification of the d-vector of the triplet, which is related to the antinodal direction of the gap function and determines whether the superconductor is topological. We perform self-consistent analysis of the vortex state properties in a nematic spin-triplet px-wave superconductor. We first derive a Ginzburg-Landau theory to determine the shape of the vortex and vortex lattice. We find the spatial profile of the isolated vortex is elongated along the antinodal direction, and the vortex lattice is a distorted triangular lattice elongated along x, becoming square in the specific case of a small circular Fermi surface. Finally, we calculate the local density of states self-consistently for an isolated vortex and the vortex lattice using the microscopic Bogoliubov-de Gennes equation. We find that the profile of the local density of states at low in-gap energies is always elongated along the antinodal direction. Our findings are valuable for the experimental detection of the antinodal direction of the gap function in nematic triplet superconductors, and subsequently the identification of the topological character of the superconducting state as in CuxBi2Se3. Related Articles | Metrics

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Self-trapped Excitons in Metal Halide Perovskites  ZHANG Qin-kai , WANG Yu-xiao , ZHANG Chun-feng Progress in Physics    2023, 43 (6): 161-177.   DOI: 10.13725/j.cnki.pip.2023.06.001 Abstract （1238）      PDF （9908KB）（1387）       In polar crystals, excited electron-hole pairs can be captured by the deformation potential field created by lattice distortion upon photoexcitation, due to strong electron-phonon interactions, thereby forming self-trapped excitons. Metal halide perovskites are semiconductors that display efficient self-trapped exciton luminescence in various systems due to their ionic crystal nature with strong electron-phonon interactions and a deformable lattice. Consequently, they are considered ideal for creating high-quality white light sources. However, the understanding of the self-trapped exciton luminescence mechanism in metal halide perovskites is still relatively scarce and lags far behind the development of devices. To this end, this paper summarizes the recent research progress on the formation conditions, formation mechanism and related excited state dynamics of self-trapped excitons in metal halide perovskites semiconductors from the perspective of the fundamental physics of self-trapped excitons, and gives an outlook on the future research based on the self-trapped exciton mechanism in this system, so as to provide a clearer physical image for the study of self-trapped excitons in this system Related Articles | Metrics

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Environmental Stability of 2D Transition Metal Dichalcogenides ZHOU Zhen-jia , XU Jie , GAO Li-bo Progress in Physics    2023, 43 (4): 97-116.   DOI: 10.13725/j.cnki.pip.2023.04.001 Abstract （1053）      PDF （837KB）（1138）       Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with a unique unity of favorable electronic and mechanical properties have been developed for fundamental studies and applications in electronics, spintronics, optoelectronics, energy harvesting and catalysis. However, as they are unstable under harsh conditions, and prone to degradation in the ambient environment, most TMDCs applications are limited. In this review, we analyze the recent advances in the research of environmental stability in TMDCs, covering the latest growth methods, the fundamental mechanisms for stability and kinds of routes to protect 2D TMDCs materials from aging and deterioration. By analyzing key factors that affect TMDCs stability from the growth process, we present a short review of optimizing growth methods for improving the stability of TMDCs. Finally, by providing insights into existing factors, this review is expected to guide the growth of stable TMDCs, which could lead to a new potential approach to growing advanced materials and designing more unexplored heterostructures.  Related Articles | Metrics

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Low-Frequency Raman Detection of Antiferromagnetic Spin Waves in Cr 2O 3 Dong Biao , CUI Jun , TIAN Yuan-zhe , WU Di , ZHANG Qi Progress in Physics    2023, 43 (5): 142-150.   DOI: 10.13725/j.cnki.pip.2023.05.002 Abstract （989）      PDF （4272KB）（729）       The antiferromagnetic (AFM) spin waves are promising for being utilized in highspeed and energy-efficient information processing. However, the excitation and detection of terahertz spin waves in AFM systems is challenging. Here, we demonstrate low-frequency Raman spectroscopy as a powerful tool for spin-wave detection in AFM systems. We present a systematic study of AFM magnons in Cr2O3, a prototypical uniaxial antiferromagnet, via Raman measurements down to 2.3 cm−1 (69 GHz). We resolved the magnon Zeeman splitting and the spin-flop transition. We further determined the sign of angular momentum of the magnon branches via polarization-resolved Raman processes. We also obtained the anisotropy energy, the g-factor, and the spin-flop field of Cr2O3 as a function of temperatures and magnetic fields. A spin-wave renormalization theory accounts for all experimental observations.  Related Articles | Metrics

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Progress in First-Principles Methods for Simulation of Warm Dense Matter ZHANG Hang, CHEN Mo-han Progress in Physics    2024, 44 (2): 49-72.   DOI: 10.13725/j.cnki.pip.2024.02.001 Abstract （977）      PDF （2466KB）（779）       Warm Dense Matter (WDM) represents a transitional state of matter situated between condensed matter and plasma, emerging as a cutting-edge research direction within the realms of planetary physics, laboratory astrophysics, and inertial confinement fusion in the field of high-energy density physics. WDM is characterized by significant quantum effects, partial ionization, strong coupling, electron degeneracy, and thermal effects, necessitating a description based on fundamental quantum mechanical theories. In recent years, simulations and calculations based on quantum mechanics’ first principles have rapidly advanced, increasingly becoming an effective tool for a deeper understanding of WDM properties. On one hand, applying First Principles widely used in condensed matter physics and materials science to WDM poses considerable challenges, especially under extreme conditions such as broad temperature ranges and high pressures, which require continuous improvements to existing first-principle algorithms and software. On the other hand, the rapid development of machine learning-based molecular dynamics methods offers new tools for simulating WDM. In this review, we initially revisit traditional first principles applicable to WDM simulations, including Kohn-Sham Density Functional Theory and Orbital-free Density Functional Theory. Subsequently, we introduce newly developed methods and software, such as Extended First Principles Molecular Dynamics and Stochastic Density Functional Theory, the latter of which has been implemented in the domestically developed open-source density functional theory software, Atomic-orbital Based Ab-initio Computation at UStc (ABACUS). These innovative approaches significantly boost the computational scale and efficiency of WDM studies, thereby elevating the precision of structural, dynamical, and transport coefficient calculations related to WDM Related Articles | Metrics

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Recent Progress on the Effect of the Electronic Structure on Electrocatalytic Performance of Single Atom Catalysts HE Yue-xuan, WANG Tong-hui, WEN Zi, JIANG Qing Progress in Physics    2024, 44 (3): 136-156.   DOI: 10.13725/j.cnki.pip.2024.03.004 Abstract （949）      PDF （2081KB）（406）       Single atom catalysts (SACs) are promising candidates for various catalytic systems due to their unique electronic structures and the highest atom utilization. Modulating the electronic structure of SACs catalysts is the key to its further development, can optimize the adsorption and bonding energies of the catalysts by regulating the electronic properties, and thus improves the catalytic activity and stability. Herein, we provide a comprehensive understanding of SACs in catalysis through their electronic structures and their associated knowledges. Various electronic properties have been discussed, such as energy band structure, orbital hybridization and associated spin states, etc. Electrocatalysis as a technology for reducing carbon emissions and utilizing renewable energy sources which can address growing pollution problems, is receiving increasing attention, making the design of high-performance catalysts critical. From this review, we discusse how the electronic structure of SACs affects their electrochemical catalytic performance and explore its relationship with activity and stability of SACs. The understanding of the fundamentals of electronic structures in catalytic processes can provide rational guidance for the design of catalysts in various catalytic reactions in the future Related Articles | Metrics

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Research Progress on the Regulation of Metal-Site Bismuth Doping in Halide Perovskites HUANG Xiao-rui, SUN Yue, HE Sheng-rong, XING Jun Progress in Physics    2024, 44 (2): 73-95.   DOI: 10.13725/j.cnki.pip.2024.02.002 Abstract （940）      PDF （8816KB）（1191）       Related Articles | Metrics

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Research Progress on Single-Mode Regulation Methods for Whispering Gallery Mode Microcavities LIU Shuo, WANG Yu-chen, WANG Xiu-hua, HOU Rui Progress in Physics    2023, 43 (4): 117-130.   DOI: 10.13725/j.cnki.pip.2023.04.002 Abstract （849）      PDF （483KB）（3141）       Whispering gallery mode (WGM) microcavities have attracted wide attention due to their small mode volume, ultra-high Q value, and low threshold. However, in rotationally symmetric WGM microcavities, multiple longitudinal mode laser radiation can be generated, and the directionality of the radiation is poor, which limits its practical applications. Finding effective methods to achieve single-mode radiation of WGM lasers is a key issue for microcavity lasers to move toward practical applications. This review focuses on several methods of single-mode modulation of WGM lasing in recent years, including reducing cavity size, adding mode selection structure, based on the vernier effect, parity-time symmetry breaking, deformed microcavity, etc. This review aims to provide a reference for researchers in related fields and deepen their understanding of the physical mechanism of single-mode modulation of WGM lasing. Related Articles | Metrics

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Theoretical Insights into the Triplet-Pair State of Singlet Fissio TONG Lei, ZHANG Chun-feng Progress in Physics    2024, 44 (3): 112-122.   DOI: 10.13725/j.cnki.pip.2024.03.002 Abstract （831）      PDF （1708KB）（693）       Singlet fission is a photophysical process in organic materials where a photoexcited singlet exciton splits into two triplet excitons. This process has gained a lot of interest in the past decade for enhancing the efficiency of photovoltaic conversion. Precious work identified a crucial intermediate state in singlet fission, and the construction of the wave function for this correlated triplet-pair state poses a significant challenge. This article serves as a comprehensive introduction to theoretical models designed for constructing the wave function of the correlated triplet-pair. Subsequently, we delve into an exploration of the intricate effects of vibrational, orbital, and spin interactions on the formation and dissociation of the intermediate state. Finally, we conclude with a succinct summary of the challenges anticipated to shape the landscape of future theoretical research in this field. Related Articles | Metrics

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Recent Progress in Ultrafast Spin Dynamics in Two-Dimensional van der Waals Antiferromagnets LI Jin-yang , WU Fang-liang , ZHANG Qi Progress in Physics    2024, 44 (6): 293-308.   DOI: 10.13725/j.cnki.pip.2024.06.003 Abstract （831）      PDF （4771KB）（885）       Antiferromagnets exhibit high-speed spin responses in the terahertz frequency range and robustness against external magnetic fields, making them promising for nextgeneration high-speed, high-density spintronic devices. Recently, two-dimensional van der Waals magnetic systems, which possess rich antiferromagnetic ground states, have gained significant attention and serve as ideal platforms for studying low-dimensional antiferromagnetic physics. Detecting and controlling ultrafast spin dynamics in two-dimensional antiferromagnetic systems will lay the foundation for high-speed spintronic device applications. Antiferromagnets have no net macroscopic magnetization, making traditional optical methods, such as magneto-optical effects, challenging for detecting antiferromagnetic order in equilibrium states. However, in non-equilibrium states, the instantaneous magnetization generated by antiferromagnetic spin dynamics allows the use of time-resolved magneto-optical Kerr effect to detect coherent spin precession in antiferromagnets. Additionally, techniques such as linear dichroism spectroscopy, terahertz emission spectroscopy, and second harmonic generation have been employed in studying the dynamics of two-dimensional antiferromagnets. This paper introduces recent experimental progress on ultrafast spin dynamics in two-dimensional van der Waals antiferromagnetic systems, and briefly describes the coherent magnon excitations and corresponding mechanisms in two-dimensional antiferromagnets, including inverse magneto-optical effects/stimulated Raman scattering, orbital excitations, and exciton coupling. Furthermore, this paper discusses the critical slowing down of spin dynamics due to spin-lattice coupling effects and the amplification of coherent acoustic phonons. Related Articles | Metrics

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Attractor Dynamics in Spatial Cognition WANG Zi-qun , WANG Tao , LIU Feng Progress in Physics    2023, 43 (6): 188-201.   DOI: 10.13725/j.cnki.pip.2023.06.003 Abstract （829）      PDF （3411KB）（1039）       The mammalian navigation system comprises various kinds of neurons responsible for position perception and spatial path planning, involving the integration of multiple information sources. As a unified brain theory capable of providing explanations for complex cognitive functions like memory and decision-making, the theory of attractor dynamics can elucidate the firing dynamics of neurons and path integration in the navigation system. This review describes recent advances in attractor dynamics in spatial cognition. First, it provides a brief overview of computational neuroscience and the general theory of attractor dynamics. Subsequently, focusing on the continuous attractor dynamics, it delves into the dynamical characteristics and functional significance of head direction cells and grid cells. Finally, an extension and prospects of the attractor theory for spatial cognition are presented. Related Articles | Metrics

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Phase Transition in Black Phosphorus Induced by Thermal Driven Diffusion of Metal CAO Tianjun , SHAN Junjie , WANG Gang, LIN Junhao, LIANG Shijun, MIAO Feng Progress in Physics    2024, 44 (1): 1-8.   DOI: 10.13725/j.cnki.pip.2024.01.001 Abstract （758）      PDF （6736KB）（696）       Two-dimensional (2D) materials are atomically flat and can be stacked into van der Waals heterostructures, as well as contain abundant physical phenomena and excellent electrical properties. The study of phase transition behavior of 2D materials has been the frontier of condensed matter physics and materials science. In our study, the stage-controlled phase transition induced by thermal-driven metal diffusion in black phosphorus (BP) is realized for the first time. Through thermal annealing treatment of the BP-In interface, the phase transition phenomenon from BP pure phase to BP/InP mixed phase and then to InP pure phase is observed. Combined with the characterization techniques of transmission electron microscopy and Raman spectroscopy, the mechanism responsible for phase transition is deeply analyzed, revealing that the thermal-driven metal diffusion behavior in BP-In is the main inducement of phase transition. The two key threshold temperatures (initiation of phase transition and transformation of pure phase) during the stepwise phase transition are obtained by manipulating the two degrees of freedom (temperature and time) which affect the energy supply in the thermal driving, where are 300 and 350 °C , respectively. This study provides more possibilities for expanding the applications of BP-based electronic and optoelectronic devices.  Related Articles | Metrics

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Image Sensor Based on Halide Perovskite ZHANG Qiang, DONG Hao-tian, BAO Chun-xiong Progress in Physics    2024, 44 (6): 278-292.   DOI: 10.13725/j.cnki.pip.2024.06.002 Abstract （720）      PDF （5446KB）（541）       Image sensors have extensive applications in both industrial and everyday settings. For example, X-ray sensors are widely used in medical imaging and security screening; visible light sensors are essential in facial recognition and smart devices; near-infrared sensors are crucial for biometric identification. Currently, these image sensors mainly utilize photodetectors based on silicon, germanium, or III-V group semiconductors. However, these sensors exhibit certain limitations, such as low light utilization efficiency in color image sensors and the occurrence of moiré patterns. Metal halide perovskites have emerged as a promising material for high-performance photodetectors due to their excellent optoelectronic properties, including high light absorption coefficients, tunable bandgaps, and high defect tolerance. This review summarizes the research advancements in image sensors based on metal halide perovskites, evaluates the current performance gap between these sensors and commercial devices, and suggests potential improvements to bridge this gap. Related Articles | Metrics

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Wave Velocity Measurement and Modulation of Surface Acoustic Waves in Piezoelectric Materials  WANG Ren-fei, LIU Xiao, WU Meng-meng, LIN Xi, LIU Yang Progress in Physics    2024, 44 (3): 103-111.   DOI: 10.13725/j.cnki.pip.2024.03.001 Abstract （705）      PDF （4278KB）（918）       In addition to the well-known conventional acoustic wave propagation mode in three-dimensional solids, there exists the surface acoustic wave propagation mode where energy is only concentrated near the two-dimensional interface. In this work, utilizing the piezoelectric and inverse piezoelectric effects from GaAs substrates, we achieve the conversion between radiofrequency electromagnetic waves and surface acoustic waves with planar interdigital transducers, and successfully measure the surface acoustic wave velocity on a sample with a dimension of only 4 mm using superheterodyne-scheme lock-in technique, yielding a result of (2.9±0.1) km/s. We also fabricate a uniaxial stress cell with piezoelectric ceramics, capable of applying uniaxial strains up to approximately 10−4 to the sample, and observe the influence of strain on the surface acoustic wave velocity. We measure the surface acoustic wave velocity of the important semiconductor GaAs under stress, demonstrating the capability of this velocity measurement technique to probe the internal mechanical properties of solids in situ. The wave velocity measurements based on planar interdigital transducers overcome the macroscopic size requirements of traditional time-of-flight and standing wave methods. The superheterodyne-scheme lock-in technique established in this article has replaced the commercial vector network analyzers for measuring surface acoustic wave velocity, enabling possible future applications with low power input and high phase stability. As the measurement setup can also be used for experimental teaching related to solid-state physics, this work provides detailed parameters and fabrication processes for surface acoustic wave devices and homemade stress cell. Related Articles | Metrics

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Working Memory: Mechanisms and Modeling Approaches YANG Fan, QIAN Rui-xin, WANG Tao Progress in Physics    2024, 44 (5): 243-258.   DOI: 10.13725/j.cnki.pip.2024.05.002 Abstract （685）      PDF （2967KB）（856）       Working memory, a cornerstone of human cognition, allows us to temporarily hold and manipulate information. The delayed response experiment is a fundamental tool for understanding working memory. By inserting a delay between the presentation of stimuli and the behavioral decision, researchers can probe the neural mechanisms underlying information maintenance and manipulation during this delay period. This review delves into the delayed response paradigm and introduces attractor dynamics as a potential mechanism for working memory function. We then systematically explore two common methods for analyzing working memory networks: trajectory tracking, and energy landscape and flux theory. Finally, we summarize the key features of these two dynamical approaches and provide an outlook for future directions of working memory research. Related Articles | Metrics

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Progress on High-Pressure Structure and Properties of Phosphorus and Phosphide HUANG Ye-hua, GUO Zhen-yuan, LI Jun-kai, YANG Xin, GOU Hui-yang Progress in Physics    2024, 44 (3): 123-135.   DOI: 10.13725/j.cnki.pip.2024.03.003 Abstract （651）      PDF （6131KB）（905）       Phosphorus，a group V non-metallic element, exhibits a unique electronic structure along with excellent optical, electrical and mechanical properties, and has a wide range of application prospects. Recent studies have demonstrated that phosphorus and phosphides are easily affected and regulated by external fields and have rich physical and chemical properties under high pressure. In addition, the unique structure and electronic properties of phosphorus and phosphides give them many physical properties that differ from those of traditional materials. Therefore, the use of high pressure to induce structural transformation and superconducting transformation in phosphorus and phosphides has become the focus of high-pressure research. In this paper, the structural, electrical, and optical responses of black phosphorus, germanium phosphide, and arsenic phosphide under high-pressure conditions are reviewed and discussed. Furthermore, we also explore the structure-activity relationships between the structures and physical properties and forecast the future research directions of phosphides under high pressure. Related Articles | Metrics

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Investigation on the Electrical and Thermal Transport Properties of BiCuXO (X=S, Se, Te) Crystals TIAN Hao, DONG Song-tao, LI Yi-chi, LÜ Yang-yang, ZHOU Jian, CHEN Yan-bin, YAO Shu-hua Progress in Physics    2024, 44 (6): 259-277.   DOI: 10.13725/j.cnki.pip.2024.06.001 Abstract （625）      PDF （10894KB）（482）       BiCuXO (X=S, Se, Te), a layered oxide material, has garnered significant attention due to its exceptional electrical transport properties and inherently low thermal conductivity, positioning it as a prospective candidate for high-performance thermoelectric applications. The optimization of material physical properties is intrinsically linked to an in-depth investigation of the crystallographic properties. This study initially presents a meticulous account of the growth procedures for BiCuXO crystals, elucidating the enhancement of electrical transport characteristics through the modulation of carrier concentrations via growth methodologies and elemental doping. A comparative analysis with ceramic samples documented in the literature is also provided. Subsequently, the paper delves into the electrical and thermal transport properties of BiCuXO crystals. The electrical transport properties encompass conductive behavior, scattering mechanisms, and magnetic resistance evolution. The thermal transport performance is mainly studied through inelastic neutron scattering and Raman experiments, combined with first principles calculations to investigate the physical mechanism of its extremely low thermal conductivity. The paper culminates with an exposition on the application of BiCuSeO crystals in photothermal electricity, harnessing the thermoelectric effect. By summarizing the growth methodologies of BiCuXO crystals and examining their electrical, thermal, and photothermal properties, this paper endeavors to offer theoretical insights and experimental guidance for the enhancement of BiCuXO material performance. Related Articles | Metrics

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Potential Impurity Effect in Twisted Bilayer Graphene LIU Ze-zhong , WANG Da Progress in Physics    2023, 43 (5): 151-160.   DOI: 10.13725/j.cnki.pip.2023.05.003 Abstract （622）      PDF （5362KB）（450）       Flat band has attracted more and more interest in recent years, motivated by its discovery in twisted bilayer graphene (TBG). In this work, we report our study of the impurity effect on this flat band system, which is an important issue for real materials. Employing the Lanczos recursive method, we solve the local density of states (LDOS) around a potential impurity. We find for large impurity size, a series of bound states are formed inside the impurity, and the flat band peak in LDOS is suppressed near the impurity boundary and shifted by the impurity potential deep inside the impurity. As the impurity size becomes smaller, the effect on the flat band becomes weaker, as anticipated from the large scale of the underlying Wannier function. This property distinguishes with the usual flat band systems with small localized Wannier orbitals, and indicates the flat band in TBG is more stable against small-size impurities.  Related Articles | Metrics