Strong Coulomb Interaction Research Articles

Tunneling Proton Grotthuss Transfer Channels by Hydrophilic-Zincophobic Heterointerface Shielding for High-Performance Zn-MnO2 Batteries.

Hollandite-type manganese dioxide (α-MnO2) is recognized as a promising cathode material upon high-performance aqueous zinc-ion batteries (ZIBs) owing to the high theoretical capacities, high working potentials, unique Zn2+/H+ co-insertion chemistry, and environmental friendliness. However, its practical applications limited by Zn2+ accommodation, where the strong coulombic interaction and sluggish kinetics cause significant lattice deformation, fast capacity degradation, insufficient rate capability, and undesired interface degradation. It remains challenging to accurately modulate H+ intercalation while suppressing Zn2+ insertion for better lattice stability and electrochemical kinetics. Herein, proton Grotthuss transfer channels are first tunneled by shielding MnO2 with hydrophilic-zincophobic heterointerface, fulfilling the H+-dominating diffusion with the state-of-the-art ZIBs performance. Local atomic structure and theoretical simulation confirm that surface-engineered α-MnO2 affords to the synergy of Mn electron t2g-eg activation, oxygen vacancy enrichment, selective H+ Grotthuss transfer, and accelerated desolvation kinetics. Consequently, fortified α-MnO2 achieves prominent low current density cycle stability (≈100% capacity retention at 1C after 400 cycles), remarkable long-lifespan cycling performance (98% capacity retention at 20C after 12000 cycles), and ultrafast rate performance (up to 30C). The study exemplifies a new approach of heterointerface engineering for regulation of H+-dominating Grotthuss transfer and lattice stabilization in α-MnO2 toward reliable ZIBs.

The ordered lattice host framework induced guest Li+ disordering in high performance cobalt-free Ni-rich cathode materials

Recently, due to high price, resource shortage and unstable supply of cobalt, the development of low-cost cobalt-free Ni-rich cathodes has attracted extensive attention with the ever-increasing lithium-ion batteries (LIBs) industry. Selecting cost-effective elements to replace cobalt in Ni-rich cathodes is urgent. However, the principle of structural design of Ni-rich cathode remains unclear, hampering the selection of alternative elements. Herein, the cobalt-free cathodes of LiNi0.95Mg0.05O2 (NiMg) and LiNi0.95Mn0.05O2 (NiMn) are designed as alternatives to LiNi0.96Co0.04O2 (NiCo). NiMg has comparable cycle stability with NiCo, while NiMn has inferior cycle performance. Reverse Monte Carlo modelling was used to generate structural model and uncover local structure by fitting pair distribution function. It reveals Mn causes more severe Jahn-Teller distortions and disordered lattice host framework (Ni0.95M0.05O2, M = Co/Mn/Mg) than Co and Mg due to the strong size effect and coulomb interactions of Mn in Ni0.95Mn0.05O2 layer. The outstanding cycle stability of NiMg and NiCo originates from the ordered lattice host frameworks, which relieve stress and inhibit particle breakage during cycle. Meanwhile, the ordered lattice host framework induced guest Li+ disordering reduces Li+ diffusion energy barrier, improving the rate capability. This study provides a new perspective for the structural design of cobalt-free Ni-rich cathodes.

Link between T-Linear Resistivity and Quantum Criticality in Ambipolar Black Phosphorus.

The interplay between strong Coulomb interactions and kinetic energy leads to intricate many-body competing ground states owing to quantum fluctuations in 2D electron and hole gases. However, the simultaneous observation of quantum critical phenomena in both electron and hole regimes remains elusive. Here, we utilize anisotropic black phosphorus (BP) to show density-driven metal-insulator transition with a critical conductance ∼e2/h which highlights the significant role of quantum fluctuations in both hole and electron regimes. We observe a T-linear resistivity from the deep metallic phase to the metal-insulator boundary at moderate temperatures, while it turns to Fermi liquid behavior in the deep metallic phase at low temperatures in both regimes. An analysis of the resistivity suggests that disorder-dominated transport leads to T-linear behavior in the hole regime, while in the electron regime, the T-linear resistivity results from strong Coulomb interactions, suggestive of strange-metal behavior. Successful scaling collapse of the resistivity in the T-linear region demonstrates the link between quantum criticality and the T-linear resistivity in both regimes. Our study provides compelling evidence that ambipolar BP could serve as an exciting testbed for investigating exotic states and quantum critical phenomena in hole and electron regimes of 2D semiconductors.

Photo Luminescence and Radiative Carrier Losses in Monolayer Transition Metal Dichalcogenides.

The carrier losses due to radiative recombination in monolayer transition metal dichalcogenides are studied using fully microscopic many-body models. The density- and temperature-dependent losses in various Mo- and W-based materials are shown to be dominated by Coulomb correlations beyond the Hartree-Fock level. Despite the much stronger Coulomb interaction in 2D materials, the radiative losses are comparable-if not weaker-than in conventional III-V materials. A strong dependence on the dielectric environment is found in agreement with experimental results.

Formation of Polymer-like Nanochains with Short Lithium-Lithium Distances in a Water-in-Salt Electrolyte.

Water-in-salts (WiSs) have recently emerged as promising electrolytes for energy storage applications ranging from aqueous batteries to supercapacitors. Here, ab initio molecular dynamics is used to study the structure of a 21 m LiTFSI WiS. The simulation reveals a new feature, in which the lithium ions form polymer-like nanochains that involve up to 10 ions. Despite the strong Coulombic interaction between them, the ions in the chains are found at a distance of 2.5 Å. They show a drastically different solvation shell compared to that of the isolated ions, in which they share on average two water molecules. The nanochains have a highly transient character due to the low free energy barrier for forming/breaking them. Providing new insights into the nanostructure of WiS electrolytes, our work calls for reevaluating our current knowledge of highly concentrated electrolytes and the impact of the modification of the solvation of active species on their electrochemical performances.

Steering in-situ low-voltage phase transition from spinel to layered cathode for high-performance zinc-ion batteries

ZnV2O4, as a ternary transition metal oxides (TOMs), has garnered significant attention as a high-performance cathode for zinc-ion batteries (ZIBs) primarily due to its high theoretical capacity and abundance. However, its densely-packed lattice structure and strong coulomb interactions with the guest Zn2+ severely restrict the exposure of active sites and impede the diffusion kinetics. Herein, we propose an innovative in-situ low-voltage phase transition strategy and successfully trigger thorough phase transition of spinel-structured ZnV2O4 to layered-structured Zn3(OH)2V2O7⋅2H2O (ZnVOHNSs). In-depth mechanism analysis reveals that a thorough and efficient transition reaction necessitates meticulous control of the external driving force, reaction kinetics, and the reactant. The activated ZnVOHNSs with large lattice spacing and abundant oxygen vacancies provides an unobstructed pathway for accelerated ion diffusion and abundant exposed active sites for ions storage. Moreover, the inherent structure stability of ZnVOHNSs ensures exceptional reaction stability and reversibility during the Zn2+ intercalation/deintercalation process. Benefiting from these merits, the activated ZnVOHNSs cathode exhibits high reversible capacity and extraordinary rate capability (achieving 369 and 233 mAh g−1 at 0.1 and 20 A g−1, respectively), which exceeds most reported cathode materials in ZIBs. This work unveils the critical phase transition mechanism and offers insight into electrode design for advanced batteries.

Doping-dependent charge- and spin-density wave orderings in a monolayer of Pb adatoms on Si(111)

In this work we computed the phase diagram as a function of temperature and doping for a system of lead adatoms allocated periodically on a silicon (111) surface. This Si(111):Pb material is characterized by a strong and long-ranged Coulomb interaction, a relatively large value of the spin-orbit coupling, and a structural phase transition that occurs at low temperature. In order to describe the collective electronic behavior in the system, we perform many-body calculations consistently taking all these important features into account. We find that charge- and spin-density wave orderings coexist with each other in several regions of the phase diagram. This result is in agreement with the recent experimental observation of a chiral spin texture in the charge density wave phase in this material. We also find that the geometries of the charge and spin textures strongly depend on the doping level. The formation of such a rich phase diagram in the Si(111):Pb material can be explained by a combined effect of the lattice distortion and electronic correlations.

Unraveling the strain tuning mechanism of interlayer excitons in WSe2/MoSe2 heterostructure

Atomically thin transition metal dichalcogenides (TMDs) exhibit rich excitonic physics, due to reduced dielectric screening and strong Coulomb interactions. Especially, some attractive topics in modern condensed matter physics, such as correlated insulator, superconductivity, topological excitons bands, are recently reported in stacking two monolayer (ML) TMDs. Here, we clearly reveal the tuning mechanism of tensile strain on interlayer excitons (IEXs) and intralayer excitons (IAXs) in WSe2/MoSe2 heterostructure (HS) at low temperature. We utilize the cryogenic tensile strain platform to stretch the HS, and measure by micro-photoluminescence (μ-PL). The PL peaks redshifts of IEXs and IAXs in WSe2/MoSe2 HS under tensile strain are well observed. The first-principles calculations by using density functional theory reveals the PL peaks redshifts of IEXs and IAXs origin from bandgap shrinkage. The calculation results also show the Mo-4d states dominating conduction band minimum shifts of the ML MoSe2 plays a dominant role in the redshifts of IEXs. This work provides new insights into understanding the tuning mechanism of tensile strain on IEXs and IAXs in two-dimensional (2D) HS, and paves a way to the development of flexible optoelectronic devices based on 2D materials.

Spotlight: Visualization of Moiré Quantum Phenomena in Transition Metal Dichalcogenide with Scanning Tunneling Microscopy.

Transition metal dichalcogenide (TMD) moiré superlattices have emerged as a significant area of study in condensed matter physics. Thanks to their superior optical properties, tunable electronic band structure, strong Coulomb interactions, and quenched electron kinetic energy, they offer exciting avenues to explore correlated quantum phenomena, topological properties, and light-matter interactions. In recent years, scanning tunneling microscopy (STM) has made significant impacts on the study of these fields by enabling intrinsic surface visualization and spectroscopic measurements with unprecedented atomic scale detail. Here, we spotlight the key findings and innovative developments in imaging and characterization of TMD heterostructures via STM, from its initial implementation on the in situ grown sample to the latest photocurrent tunneling microscopy. The evolution in sample design, progressing from a conductive to an insulating substrate, has not only expanded our control over TMD moiré superlattices but also promoted an understanding of their structures and strongly correlated properties, such as the structural reconstruction and formation of generalized two-dimensional Wigner crystal states. In addition to highlighting recent advancements, we outline upcoming challenges, suggest the direction of future research, and advocate for the versatile use of STM to further comprehend and manipulate the quantum dynamics in TMD moiré superlattices.

Theoretical Perspective of Enhancing Order in n-Doped Thermoelectric Polymers through Side Chain Engineering: The Interplay of Counterion-Backbone Interaction and Side Chain Steric Hindrance.

Donor-acceptor (D-A) copolymers doped with n-type dopants are widely sought after for their potential in organic thermoelectric devices. However, the existing structural disorder significantly hampers their charge transport and thermoelectric performance. In this Letter, we propose a mechanism to mitigate this disorder through side chain engineering. Utilizing molecular dynamics simulations, we demonstrate that strong Coulomb interactions between counterions and charged polymer backbones induce a transition in the stacking arrangement of the polymer backbones from a slipped to a vertical configuration. However, the presence of side chain steric hindrance impedes the formation of closely packed and ordered vertical stacking arrangements, resulting in greater distances between adjacent backbones and a higher level of structural disorder in the doped films. Therefore, we propose minimizing side chain steric hindrance to enhance the structural order in doped films. Our findings provide essential insights for advancing high-performance thermoelectric polymers.

Doping induced multiferroicity and quantum anomalous Hall effect in α-In2Se3 thin films

In flatband materials, the strong Coulomb interaction between electrons can lead to exotic physical phenomena. Recently, α-In2Se3 thin films were found to possess ferroelectricity and flat bands. In this work, using first-principles calculations, we find that for the monolayer, there is a Weyl point at Γ in the flatband, where the inclusion of the spin–orbit coupling opens a gap. Shifting the Fermi level into the spin–orbit gap gives rise to nontrivial band topology, which is preserved for the bilayer regardless of the interlayer polarization couplings. We further calculate the Chern number and edge states for both the monolayer and bilayer, for which the results suggest that they become quantum anomalous Hall insulators under appropriate dopings. Moreover, we find that the doping-induced magnetism for the In2Se3 bilayer is strongly dependent on the interlayer polarization coupling. Therefore, doping the flat bands in In2Se3 bilayer can also yield multiferroicity, where the magnetism is electrically tunable as the system transforms between different polarization states. Our study, thus, reveals that multiferroicity and nontrivial band topology can be unified into one material for designing multifunctional electronic devices.

Carbon Dots as Ligand Operons to Expand Cluster Size Distribution for High Load‐bearing Liquid Superlubricity

AbstractAdding additives (e.g., carbon dots, CDs) to liquid lubricants is an effective method for enhancing their load‐bearing capacity and friction reduction. However, it is challenging to simultaneously impart high load‐bearing capacity and superlubricity for them (e.g., ionic liquid analogs, ILAs) through this strategy due to strong Coulombic interactions. With CDs as a competing ligand operon, the cluster size distribution can be expanded, conferring superlubricity with ultrahigh load‐bearing capacity (>705 MPa, the highest value of CDs‐based superlubricious materials thus far) for CDs/ILAs. In particular, methodologies such as Raman, 1H‐NMR, fourier transform infrared spectroscopy, and laser particle size analysis are employed to characterize the evolution of their H‐bonding interactions and particle size distribution. CDs can act as competing ligands and enable CDs/ILAs to form systems with ultra‐low coefficient of friction and wear consisting of a mixture of large and small clusters. The mixed and expanded size clusters facilitate the reduction of the viscosity for CDs/ILAs under shear, thereby reducing the interfacial shear resistance during superlubricity, while the CDs within them efficiently transfer the normal bearing loads. The progress is made from the perspective of cluster particle size distribution rather than individual additive properties, providing a new avenue for designing ILAs‐based superlubricious materials.

Excitonic Rydberg States in a Trilayer to Monolayer H2-Aided CVD-Grown Large-Area MoS2 Film with Excellent UV to Visible Broad Band Photodetection Applications.

The diverse nature of optoelectronic properties of few-layer or monolayer MoS2 is generally dominated by A and B excitons. Occasionally, strong Coulombic interactions within the 2D monolayer led to the creation of hydrogen-like Rydberg states of excitons in MoS2 similar to other 2D monolayers. In this paper, a simple process is used to convert trilayer MoS2 films to a monolayer by introducing H2 gas during chemical vapor deposition. Remarkably, alongside the usual A, B excitons, and A- trion, the appearance of the Rydberg states is evidenced by photoluminescence spectra even at room temperature; also, there is an increase in their areal percentage with an increase in H2 content. The s-type excited Rydberg states up to the fourth order (n = 5) and third order (n = 4) of A and B excitons, respectively, have been probed from the photoluminescence spectra at 93 K. Unprecedentedly, the first-order derivative of room-temperature photocurrent spectrum reveals the Rydberg states concurrently and elaboratively. Furthermore, the large-area MoS2 films exhibit photoresponse in a broad UV to visible region with excellent photosensitivity (∼102) toward both UV and visible lights. Not only does this provide a profound understanding of the excitonic Rydberg states but also highlights the considerable potential of large-area monolayer MoS2 overcoming the difficulty of tiny flake-related 2D device endeavors.

Quantum plasmonics pushes chiral sensing limit to single molecules: a paradigm for chiral biodetections

Chiral sensing of single molecules is vital for the understanding of chirality and their applications in biomedicine. However, current technologies face severe limitations in achieving single-molecule sensitivity. Here we overcome these limitations by designing a tunable chiral supramolecular plasmonic system made of helical oligoamide sequences (OS) and nanoparticle-on-mirror (NPoM) resonator, which works across the classical and quantum regimes. Our design enhances the chiral sensitivity in the quantum tunnelling regime despite of the reduced local E-field, which is due to the strong Coulomb interactions between the chiral OSs and the achiral NPoMs and the additional enhancement from tunnelling electrons. A minimum of four molecules per single-Au particle can be detected, which allows for the detection of an enantiomeric excess within a monolayer, manifesting great potential for the chiral sensing of single molecules.

Decoupling of Majorana bound states in T-shaped double-quantum-dot structure with ferromagnetic leads

The significant potential applications of Majorana bound state (MBS) in topological quantum computing manifest the importance and necessity of relevant in-depth research. To understand the physical properties of MBS, the most practical approach is to integrate it to a mesoscopic circuit and then investigate its quantum transport behaviors. In this work, we investigate the transport properties in the systems with MBS, and provide theoretical support for its further understanding and detection, by utilizing the nonequilibrium Green’s function method and scattering matrix theory. Specifically, we investigate theoretically the transport properties in a T-shaped double-quantum dot structure, by considering MBS to be coupled to the dot in the main channel, which shows that in the linear transmission region, when the level of side-coupled dot is tuned to the Fermi energy level, the contribution of MBS to the conductance is eliminated under weak and strong Coulomb interaction. The side-coupled dot is far away from the Fermi energy level, leading to different results. When Majorana zero mode is added, the linear conductance is independent of the level of the side-coupled quantum dot, and the conductance plateau appears. However, with coupling between the MBSs, the linear conductance is the same as that without coupling between the MBSs. The decoupling phenomenon of the MBS remains strong. Therefore, the signature of the MBS can be eliminated by adjusting the level of the side-coupled quantum dot or the inter-MBS coupling. When ferromagnetic leads are introduced, the appearance or disappearance of the conductance plateau is clearly dependent on the difference between the magnetic field direction and the lead polarization direction in the system, whereas the decoupling behavior of the MBS is still existent. This work contributes to further explaining the decoupling phenomenon of MBSs in a T-shaped double-quantum-dot system, and presents a theoretical approach to more in-depth understanding and detection of the MBS.

Synthesis of CoFe2O4@SiO2-NH2 and its application in adsorption of trace lead.

In this work, an amine functionalized CoFe2O4 magnetic nanocomposite material CoFe2O4@SiO2-NH2 was prepared successfully by modifying coated-CoFe2O4@SiO2 magnetic nanoparticles with 3-aminopropyltriethoxysilane (APTES) and became an efficient adsorbent for the separation and analysis of trace lead in water. The CoFe2O4@SiO2-NH2 magnetic nanoparticles were characterized using SEM, TEM, XRD, FTIR, VSM and BET techniques. Then, the adsorption mechanism was preliminarily investigated through ZETA, XPS, and adsorption kinetic experiments. The adsorption process was fitted by pseudo-second-order kinetics and a Langmuir isotherm model. The main adsorption mechanism of CoFe2O4@SiO2-NH2 towards lead ions was the chelation between the amino groups of CoFe2O4@SiO2-NH2 and lead cations, as well as the strong Coulomb interaction between the electron donor atoms O and N in the surface of CoFe2O4@SiO2-NH2 and lead cations. The adsorption capacity is 74.5 mg g-1 and the adsorbent can be reused 5 times. Hence, this prepared CoFe2O4@SiO2-NH2 could find potential applications for the removal of trace metal ions in surface water.

Ion-Molecule Co-Confining Ammonium Vanadate Cathode for High-Performance Aqueous Zinc-Ion Batteries.

Vanadium-based cathode materials have attracted great attention in aqueous zinc-ion batteries (AZIBs). However, the inferior ion transport and cyclic stability due to the strong Coulomb interaction between Zn2+ and the lattice limit their further application. In this work, CO2 molecules are in situ embedded in the interlayer structure of NH4V4O10 by decomposing excess H2C2O4·2H2O in the main framework, obtaining an ion-molecule co-confining NH4V4O10 for AZIB cathode material. The introduced CO2 molecules expanded the interlayer spacing of NH4V4O10, broadened the diffusion channel of Zn2+, and stabilized the structure of NH4V4O10 as the interlayer pillars together with , which effectively improved the Zn2+ diffusion kinetics and cycle stability of the electrode. In addition, the binding between and the host framework is stabilized via hydrogen bonds with CO2 molecules. NVO-CO2-0.8 exhibited excellent specific capacity (451.1mAhg-1 at 2 Ag-1), cycle stability (214.0mAhg-1 at 10Ag-1 after 1000 cycles) and rate performance. This work provides new ideas and approaches for optimizing vanadium-based materials with high-performance AZIBs.

Modulate the Strong Exciton Effect by Na+ Coordination-Induced Trap States: Efficient Photocatalytic H2O2 Production.

Due to the strong Coulomb interaction, in most polymer photocatalysts, electron-hole pairs exist in the form of excitons rather than free charge carriers. The giant excitonic effect is a key obstacle to generating free charge carriers. Therefore, effectively regulating the exciton effect is the first step to achieving optimized carrier separation. Here, we used C-ring/g-C3N4 as the prototypical model system to design a photocatalyst with a Na-coordination-induced trap state. We demonstrate that the excitons can be effectively dissociated into charge carriers by combining with the trap state formed by Na doping sites. Encouragingly, signals from the dissociation of excitons into carriers were observed by ultrafast transient spectroscopy. Benefiting from the enhanced exciton dissociation, Na-C/CN displayed a H2O2 production rate of 17.4 mmol·L-1·h-1 with an apparent quantum efficiency up to 26.9% at 380 nm, which is much higher than many other g-C3N4-based photocatalysts. This work explains the effect of cation doping on the exciton-carrier behavior in polymers. Also, it provides a new way to regulate the exciton effect.

Exploring the Possibility of Aluminum Plating/Stripping from a Non-Corrosive Al(OTF)3-Based Electrolyte

Aluminum abundance sources and the high theoretical volumetric capacity of Aluminum metal make Aluminum Batteries (ABs) promising energy storage systems[1]. Moreover, the low cost, sustainability, and low reactivity of Al in the air due to its passivation layer are advantageous in comparison to Li[2]. However, developing appropriate electrolytes for Aluminum batteries is a challenging topic that hinders their practical use[3]. Of particular concern is that the high charge density of the Al cation results in strong Coulombic interaction with the counter anions and solvents, which negatively impacts the solvation behavior of Al salts [4]. A non-corrosive ternary electrolyte, composed of Al(OTF)3/NMA/urea in the molar fraction of 0.05/0.76/0.19 respectively, was tested for Al battery system as an alternative to the common chloroaluminate-based electrolytes to enable Al plating/stripping[5]. Herein, several techniques, such as scanning electron microscope/energy-dispersive X-ray spectroscope (SEM/EDX), operando Optical microscopy examination, electrochemical quartz crystal (EQCM) and Gas chromatography (GC) were used to explore the Al electrodeposition from this electrolyte. Yet, the hydrogen evolution reaction was found to be associated with electrochemical activities observed in this multicomponent electrolyte rather than Al electrodeposition.

(Invited) Interlayer Excitons in Two-Dimensional Perovskite/Monolayer Transition Metal Dichalcogenide Heterostructures

The emergence of two-dimensional (2D) materials has intrigued a great deal of research on novel physical phenomena and various functional applications due to their particular crystal structures and reduced dimensionality. Unlike 3D materials, bulks of 2D materials can be easily thinned to atomic thickness by mechanical exfoliation and atomically thin 2D materials can be arbitrarily stacked to form vertical van der Waals (vdW) heterostructures, which could inherit the unique characteristics of the constituent layers and even exhibit new properties not possessed by them. Particularly, when type-Ⅱ vdW heterostructures are excited, the positive and the negative charges would reside in the different layers after the charge transfer but be limited within a short distance due to the strong quantum confinement effect of 2D materials, leading to strong Coulomb interaction and the formation of interlayer excitons (IXs). IXs are generally equipped with orientated dipole moment and long lifetime, making them ideal media for the future interconnects between optical transmission and electronic computation. Currently, studies on IXs are mainly focused on the vdW heterostructures formed by monolayers of transition-metal dichalcogenides (TMDs). Here, I will first talk about vdW heterostructures formed by 2D perovskites and TMDs for studying IXs. Stacking different kinds of 2D perovskites and TMDs, formation of IXs is confirmed by excitation-power-, temperature-, electric-field-dependent and time-resolved photoluminescence (PL) studies. Notably, robust IX emission can be observed regardless of the stacking sequence and geometric alignment of the constituent layers, showing great advantages over the TMD/TMD vdW heterostructures, which require special twist-angle and thermal annealing. Then, I would like to give a brief introduction on widely tuning the IX emission energy by changing the layer number of the 2D perovskite or the TMD, which shed light on the application of 2D perovskite/TMD vdW heterostructures in broad-spectrum optoelectronics. Furthermore, I would like to next talk about how the selection of organic chains in 2D perovskites influences the properties of the IXs. By using chiral 2D perovskites, the IX emission shows substantial circular polarization and the polarization direction is only related to the chirality of the molecules regardless of the excitation scheme or any other external field, which could open up new passages for controlling valley- or spin-polarization of IXs. By introducing molecules with different dielectric constants, the dielectric screening strength in the vdW heterostructure is changed and hence the binding energy of the IXs is also modified, which offers great opportunities for exploiting tunable excitonic devices and studying exciton condensation. Finally, I will also introduce IX as a non-destructive tool for probing the local phase transition at the surface of the 2D perovskite (BA)2PbI4 flakes. By spatially PL mapping of the (BA)2PbI4/WSe2 heterostructure, two different IX species can be observed to distinguish the low-temperature and the high-temperature phase respectively.