Reaction Chemistry at Discrete Organometallic Fragments on Black Phosphorus

2023-11-03T13:08:27+00:00November 3rd, 2023|Categories: Publications|Tags: |

Molecular functionalization techniques are leveraged to anchor well-defined organometallic fragments on the surface of black phosphorus. The functionalized nanosheets feature a high density of metal sites, with discrete and robust M−P bonds that are stable to subsequent transformations. The Tolman electronic parameter and steric bulk of bP are also estimated relative to molecular phosphines. Abstract Black phosphorus (bP) is a two-dimensional van der Waals material unique in its potential to serve as a support for single-site catalysts due to its similarity to molecular phosphines, ligands quintessential in homogeneous catalysis. However, there is a scarcity of synthetic methods to install single metal centers on the bP lattice. Here, we demonstrate the functionalization of bP nanosheets with molecular Re and Mo complexes. A suite of characterization techniques, including infrared, X-ray photoelectron and X-ray absorption spectroscopy as well as scanning transmission electron microscopy corroborate that the functionalized nanosheets contain a high density of discrete metal centers directly bound to the bP surface. Moreover, the supported metal centers are chemically accessible and can undergo ligand exchange transformations without detaching from the surface. The steric and electronic properties of bP as a ligand are estimated with respect to molecular phosphines. Sterically, bP resembles tri(tolyl)phosphine when monodentate to a metal center, and bis(diphenylphosphino)propane when bidentate, whereas electronically bP is a σ-donor as strong as a trialkyl phosphine. This work is foundational in elucidating the nature of black phosphorus as a ligand and underscores the viability of using bP as a basis for single-site catalysts.

Published in: "Angewandte Chemie International Edition".

Coupling Benzylamine Oxidation with CO2 Photoconversion to Ethanol over a Black Phosphorus and Bismuth Tungstate S‐Scheme Heterojunction

2023-07-01T13:07:54+00:00July 1st, 2023|Categories: Publications|Tags: |

Photoconversion of CO2 and H2O into ethanol is an ideal strategy to achieve carbon neutrality. However, the production of ethanol with high activity and selectivity is challenging owing to the less efficient reduction half-reaction involving multi-step proton coupled electron transfer (PCET), slow C-C coupling process, and sluggish water oxidation half-reaction. Herein, a two-dimensional/two-dimensional (2D/2D) S-scheme heterojunction consisting of black phosphorus and Bi2WO6 (BP/BWO) was constructed for photocatalytic CO2 reduction coupling with benzylamine (BA) oxidation. The as-prepared BP/BWO catalyst exhibits a superior photocatalytic performance toward CO2 reduction, with a yield of 61.3 μmol g−1 h−1 for ethanol (selectivity of 91%).In situ spectroscopic studies and theoretical calculations reveal that S-scheme heterojunction can effectively promote photogenerated carrier separation via the Bi-O-P bridge to accelerate the PCET process. Meanwhile, electron-rich BP acts as the active site and plays a vital role in the process of C-C coupling. In addition, the substitution of BA oxidation for H2O oxidation can further enhance the photocatalytic performance of CO2 reduction to C2H5OH. This work opens a new horizon for exploring novel heterogeneous photocatalysts in CO2 photoconversion to C2H5OH based on cooperative photoredox systems.

Published in: "Angewandte Chemie International Edition".

Electronic structure of few-layer black phosphorus from $mu$-ARPES. (arXiv:2306.00749v1 [cond-mat.mes-hall])

2023-06-02T02:29:43+00:00June 2nd, 2023|Categories: Publications|Tags: |

Black phosphorus (BP) stands out among two-dimensional (2D) semiconductors because of its high mobility and thickness dependent direct band gap. However, the quasiparticle band structure of ultrathin BP has remained inaccessible to experiment thus far. Here we use a recently developed laser-based micro-focus angle resolved photoemission ($mu$-ARPES) system to establish the electronic structure of 2-9 layer BP from experiment. Our measurements unveil ladders of anisotropic, quantized subbands at energies that deviate from the scaling observed in conventional semiconductor quantum wells. We quantify the anisotropy of the effective masses and determine universal tight-binding parameters which provide an accurate description of the electronic structure for all thicknesses.

Published in: "arXiv Material Science".

Landauer-QFLPS model for mixed Schottky-Ohmic contact two-dimensional transistors. (arXiv:2303.11107v1 [physics.app-ph])

2023-03-21T04:30:22+00:00March 21st, 2023|Categories: Publications|Tags: , |

Two-dimensional material-based field effect transistors (2DM-FETs) are playing a revolutionary role in electronic devices. However, after years of development, no device model can match the Pao-Sah model for standard silicon-based transistors in terms of physical accuracy and computational efficiency to support large-scale integrated circuit design. One remaining critical obstacle is the contacts of 2DM-FETs. In order to self-consistently include the contact effect in the current model, it is necessary to perform self-consistent calculations, which is a fatal flaw for applications that prioritize efficiency. Here, we report that the Landauer-QFLPS model effectively overcomes the above contradiction, where QFLPS means quasi-Fermi-level phase space theory. By connecting the physical pictures of the contact and the intrinsic channel part, we have successfully derived a drain-source current formula including the contact effect. To verify the model, we prepared transistors based on two typical 2DMs, black phosphorus (BP) and molybdenum disulfide (MoS2), the former having ambipolar transport and the latter showing electron-dominant unipolar transport. The proposed new formula could describe both 2DM-FETs with Schottky or Ohmic contacts. Moreover, compared with traditional methods, the proposed model has the advantages of accuracy and efficiency, especially in describing non-monotonic drain conductance characteristics, because the contact effect is self-consistently and compactly packaged as an exponential term. More importantly, we also examined the model at the circuit level. Here, we fabricated a three-bit threshold inverter quantizer circuit based on ambipolar-BP process and experimentally demonstrated that the model can accurately predict the circuit performance. This industry-benign 2DM-FET model is supposed to be

Published : "arXiv Mesoscale and Nanoscale Physics".

Rational Utilization of Black Phosphorus Nanosheets to Enhance Palladium‐Mediated Bioorthogonal Catalytic Activity for Activation of Therapeutics

2023-03-15T13:07:47+00:00March 15th, 2023|Categories: Publications|Tags: |

Pd-catalyzed chemistry has played a significant role in the growing subfield of bioorthogonal catalysis. However, rationally designing Pd nanocatalysts that meet outstanding catalytic activity and good biocompatibility poses a great challenge. Herein, we propose an innovative strategy through exploiting black phosphorous nanosheets (BPNSs) to enhance Pd-mediated bioorthogonal catalytic activity. Firstly, the electron-donor properties of BPNSs enable in situ growth of Pd nanoparticles (PdNPs) on it. Meanwhile, due to the superb reduction of Pd (II) ability, BPNSs can act as hard nucleophiles to accelerate the transmetallation in the decaging reaction process. Secondly, the lone pair electrons of BPNSs, which can firmly anchor PdNPs on their surface via Pd-P bonds. Such design endows Pd/BP with the capability to retards tumor growth by activating prodrugs. This work proposes new insights into the design of heterogeneous transition-metal catalysts (TMCs) for bioorthogonal catalysis.

Published in: "Angewandte Chemie International Edition".

An efficient model algorithm for two-dimensional field-effect transistors. (arXiv:2303.06926v1 [cond-mat.mtrl-sci])

2023-03-14T02:30:11+00:00March 14th, 2023|Categories: Publications|Tags: , |

Two-dimensional materials-based field-effect transistors (2DM-FETs) exhibit both ambipolar and unipolar transport types. To physically and compactly cover both cases, we put forward a quasi-Fermi-level phase space (QFLPS) approach to model the ambipolar effect in our previous work. This work aims to further improve the QFLPS model’s numerical aspect so that the model can be implanted into the standard circuit simulator. We first rigorously derive the integral-free formula for the drain-source current to achieve this goal. It is more friendly to computation than the integral form. Besides, it explicitly gives the correlation terms between the electron and hole components. Secondly, to work out the boundary values required by the new expressions, we develop a fast evaluation algorithm for the surface electrostatic potential based on the zero-temperature limit property of the 2DM-FET system. By calibrating the model with the realistic device data of black phosphorus (BP) and monolayer molybdenum disulfide (ML-MoS2) FETs, the completed algorithm is tested against practical cases. The results show a typical superiority to the benchmark algorithm by two orders of magnitude in time consumption can be achieved while keeping a high accuracy with 7 to 9 significant digits.

Published in: "arXiv Material Science".

Quantum Shot Noise Signatures of Two-Dimensional Semi-Dirac System. (arXiv:2303.04468v1 [cond-mat.mes-hall])

2023-03-09T04:30:24+00:00March 9th, 2023|Categories: Publications|Tags: , |

Two-dimensional ($2$D) semi-Dirac systems, such as $2$D black phosphorus and arsenene, can exhibit a rich topological phase transition between insulating, semi-Dirac, and band inversion phases when subjected to an external modulation. How these phase transitions manifest within the quantum transport and shot noise signatures remain an open question thus far. Here, we show that the Fano factor converges to the universal $Fapprox0.179$ at the semi-Dirac phase, and transits between the sub-Poissonian ($Fapprox1/3$) and the Poissonian shot noise ($Fapprox1$) limit at the band inversion and the insulating phase, respectively. Furthermore, the conductance of $2$D semi-Dirac system converges to the contrasting limit of $G/G_0 rightarrow 1/d$ and $G/G_0 rightarrow0$ at the band inversion and the insulating phases, respectively. The quantum tunneling spectra exhibits a peculiar coexistence of massless and massive Dirac quasiparticles in the band inversion regime, thus providing a versatile sandbox to study the tunneling behavior of various Dirac quasiparticles. These findings reveal the rich interplay between band topology and quantum transport signatures, which may serve as smoking gun signatures for the experimental studies of semi-Dirac systems near topological phase transition.

Published : "arXiv Mesoscale and Nanoscale Physics".

Fluorine‐Stabilized Defective Black Phosphorene as a Lithium‐Like Catalyst for Boosting Nitrogen Electroreduction to Ammonia

2023-03-03T13:07:51+00:00March 3rd, 2023|Categories: Publications|Tags: |

Electrocatalytic N2 reduction reaction (NRR) is recognized as a zero-carbon emission method for NH3 synthesis. However, to date, this technology still suffers from low yield and low selectivity associated with the catalyst. Herein, inspired by the activation of N2 by lithium metal, a highly reactive defective black phosphorene (D-BPene) is proposed as a lithium-like catalyst for boosting electrochemical N2 activation. Correspondingly, we also report a strategy for producing environmentally stable D-BPene by simultaneously constructing defects and fluorination protection based on topochemical reactions. Reliable performance evaluations show that the fluorine-stabilized D-BPene can induce a high NH3 yield rate of ~70 µg h-1 mgcat.-1 and a high Faradaic efficiency of ~26% at -0.5 V vs. RHE in an aqueous electrolyte. This work not only exemplifies the first stable preparation and practical application of D-BPene, but also brings a new design idea for NRR catalysts.

Published in: "Angewandte Chemie International Edition".

Band structures and contact points in phosphorene superlattice. (arXiv:2302.11498v1 [cond-mat.mes-hall])

2023-02-23T04:30:20+00:00February 23rd, 2023|Categories: Publications|Tags: , |

We study the band structures and the associated contact points for a phosphorene superlattice made up of two periodic areas. We use the boundary conditions to extract an equation describing the dispersion relation after obtaining the eigen-wavefunctions. We show that energy transforms into linear behavior near contact points, and fermions move at different speeds along $x$- and $y$- directions. It was discovered that the periodic potential caused additional Dirac points, which we located in $k$-space by establishing their positions. We demonstrate that the barrier height and width can be used to adjust the energy gap and modify the contact points. It might be that our findings will be useful in the development of phosphorene-based electronic devices.

Published : "arXiv Mesoscale and Nanoscale Physics".

Pseudospin-selective Floquet band engineering in black phosphorus. (arXiv:2302.00604v1 [cond-mat.mtrl-sci])

2023-02-02T02:29:26+00:00February 2nd, 2023|Categories: Publications|Tags: , |

Time-periodic light field has emerged as a control knob for manipulating quantum states in solid-state materials, cold atoms and photonic systems via hybridization with photon-dressed Floquet states in the strong coupling limit, dubbed as Floquet engineering. Such interaction leads to tailored properties of quantum materials, for example, modifications of the topological properties of Dirac materials and modulation of the optical response. Despite extensive research interests over the past decade, there is no experimental evidence of momentum-resolved Floquet band engineering of semiconductors, which is a crucial step to extend Floquet engineering to a wide range of solid-state materials. Here, based on time- and angle-resolved photoemission spectroscopy measurements, we report experimental signatures of Floquet band engineering in a model semiconductor – black phosphorus. Upon near-resonance pumping at photon energy of 340 to 440 meV, a strong band renormalization is observed near the band edges. In particular, light-induced dynamical gap opening is resolved at the resonance points, which emerges simultaneously with the Floquet sidebands. Moreover, the band renormalization shows a strong selection rule favoring pump polarization along the armchair direction, suggesting pseudospin selectivity for the Floquet band engineering as enforced by the lattice symmetry. Our work demonstrates pseudospin-selective Floquet band engineering in black phosphorus, and provides important guiding principles for Floquet engineering of semiconductors.

Published in: "arXiv Material Science".

Anisotropic Electron-Hole Excitation and Large Linear Dichroism in Two-Dimensional Ferromagnet CrSBr with In-Plane Magnetization. (arXiv:2301.13342v1 [cond-mat.mtrl-sci])

2023-02-01T02:29:22+00:00February 1st, 2023|Categories: Publications|Tags: |

The observation of magnetic ordering in atomically thin CrI$_3$ and Cr$_2$Ge$_2$Te$_6$ monolayers has aroused intense interest in condensed matter physics and material science. Studies of van de Waals two-dimensional (2D) magnetic materials are of both fundamental importance and application interest. In particular, exciton-enhanced magneto-optical properties revealed in CrI$_3$ and CrBr$_3$ monolayers have expanded the understanding of exciton physics in 2D materials. Unlike CrI$_3$ and CrBr$_3$ with out-of-plane magnetization, CrSBr has an in-plane magnetic moment, therefore, providing a good opportunity to study the magnetic linear dichroism and high order magneto-optical effects. Here, based on many-body perturbation method within density-functional theory, we have studied quasiparticle electronic structure, exciton, and optical properties in CrSBr monolayer. Strongly bounded exciton has been identified with the first bright exciton located at 1.35 eV, in good agreement with experiment of photoluminescence (Nat. Mater. 20, 1657 (2021)). Strong contrast in the optical absorption is found between the electric fields lying along the in-plane two orthogonal directions. In accordance to typical and realistic experimental setup, we show that the rotation angle of linear polarized light, either reflected or transmitted, could be comparable with those revealed in black phosphorene. Such a large linear dichroism arises mainly from anisotropic in-plane crystal structure. The magnetic contribution from the off-diagonal component of dielectric function to the linear dichroism in CrSBr is negligible. Our findings not only have provided a deep understanding of exciton-enhanced optical process in low-dimensional materials, but also have shown the potential applications of CrSBr in 2D optics and optoelectronics.

Published in: "arXiv Material Science".

Towards large-area and defects-free growth of phosphorene on Nickel. (arXiv:2301.06139v1 [cond-mat.mtrl-sci])

2023-01-18T02:29:39+00:00January 18th, 2023|Categories: Publications|Tags: |

Low-dimensional materials synthesis based on phosphorus atoms is under intense study, and it is still one of the big challenges. Phosphorene, a monolayer of black phosphorus, is one of the most promising candidates for transistor and photonics devices at atomistic thickness. However, the lack of large-scale and defects-free growth significantly obstructs its device development. Here, we demonstrate the large-scale and defect-free phosphorene synthesis on Nickel (Ni) substrate. In addition, the effect of substrate orientation on the controllable synthesis of possible allotropes has also been described. We have shown that blue phosphorene can be grown on Ni (111) and Ni (100). While {gamma}-Phosphorene, named Navy Phosphorene hereafter, can be grown on Ni (110). Furthermore, we found that the synthesis goes through phosphorus pentamers (P5) to phosphorene; P5 is a vital precursor for phosphorene synthesis. Moreover, we confirm the high accuracy of the P-Ni, and P-P potentials and show that the molecular dynamics (M.D.) approach is a powerful tool to simulate the 2D materials synthesis in the vapor phase. This work provides a solid reference to understand and control the synthesis of large-area single-crystalline monolayer phosphorene.

Published in: "arXiv Material Science".

The phonon thermal Hall angle in black phosphorus. (arXiv:2301.00603v1 [cond-mat.str-el])

2023-01-03T02:29:29+00:00January 3rd, 2023|Categories: Publications|Tags: |

The origin of phonon thermal Hall Effect (THE) observed in a variety of insulators is yet to be identified. Here, we report on the observation of a thermal Hall conductivity in a non-magnetic elemental insulator, with an amplitude exceeding what has been previously observed. In black phosphorus (BP), the longitudinal ($kappa_{ii}$), and the transverse, $kappa_{ij}$, thermal conductivities peak at the same temperature and at this peak temperature, the $kappa_{ij}/kappa_{jj}/B $ is $approx 10^{-4}$-$10^{-3}$ T$^{-1}$. Both these features are shared by other insulators displaying THE, despite an absolute amplitude spreading over three orders of magnitude. The absence of correlation between the thermal Hall angle and the phonon mean-free-path imposes a severe constraint for theoretical scenarios of THE. We show that in BP a longitudinal and a transverse acoustic phonon mode anti-cross, facilitating wave-like transport across modes and the anisotropic charge distribution surrounding atomic bonds, paving the way for coupling with magnetic field.

Published in: "arXiv Material Science".

Propagation of Visible Light in Nanostructured Niobium Stripes Embedded in a Dielectric Polymer. (arXiv:2212.12296v1 [physics.optics])

2022-12-26T02:29:23+00:00December 26th, 2022|Categories: Publications|Tags: |

Nanometric metallic stripes allow the transmission of optical signals via the excitation and propagation of surface-localized evanescent electromagnetic waves, with important applications in the field of nano-photonics. Whereas this kind of plasmonic phenomena typically exploits noble metals, like Ag or Au, other materials can exhibit viable light-transport efficiency. In this work, we demonstrate the transport of visible light in nanometric niobium stripes coupled with a dielectric polymeric layer, exploiting the remotely-excited/detected Raman signal of black phosphorus (bP) as the probe. The light-transport mechanism is ascribed to the generation of surface plasmon polaritons at the Nb/polymer interface. The propagation length is limited due to the lossy nature of niobium in the optical range, but this material may allow the exploitation of specific functionalities that are absent in noble-metal counterparts.

Published in: "arXiv Material Science".

A new efficient ab-initio approach for calculating the bending stiffness of 2D materials. (arXiv:2212.11913v1 [cond-mat.mtrl-sci])

2022-12-23T02:29:27+00:00December 23rd, 2022|Categories: Publications|Tags: , , , |

This work proposes a new efficient approach for calculating the bending stiffness of two-dimensional materials using simple atomistic tests on small periodic unit cells. The tests are designed such that bending deformations are dominating and membrane deformations are minimized. Atomistic ab-initio simulations then allow for the efficient computation of bending energies. Density functional theory is used for this. Atomistic bending energies are then compared to classical models from structural mechanics. Two different models are considered for this — one based on beam theory and one based on rigid linkage theory — and their results are compared with each other. Four different materials with 2D hexagonal (honeycomb) structure are chosen as a case study: graphene, hexagonal boron nitride, silicene, and blue phosphorene. The calculated bending stiffnesses converge with increasing unit cell size, such that small unit cells already provide accurate results that are in good agreement with the literature. Using the same atomistic tests, it is shown that the bending stiffness of graphene can still be considered constant at moderately large deformations. Apart from being efficient and accurate, the proposed approach allows for various extensions.

Published in: "arXiv Material Science".

Enhanced thermoelectric properties in phosphorene nanorings. (arXiv:2212.10260v1 [cond-mat.mes-hall])

2022-12-21T04:30:46+00:00December 21st, 2022|Categories: Publications|Tags: |

Using the tight-binding approach, we investigate the thermoelectric (TE) properties of rectangular phosphorene nanorings for both symmetrically and asymmetrically attaching to phosphorene nanoribbon leads. We design our phosphorene-based nanostructures to enhance the TE performance in the absence and the presence of perpendicular magnetic fields. Our results show that when zigzag phosphorene nanoribbons (ZPNRs) are coupled symmetrically to rectangular rings, a comparatively large band gap is induced in the electronic conductance due to the suppression of the contribution of edge states. This gives rise to a remarkable increase in the thermopower response compared to the case of pristine ZPNRs. More intriguingly, we found that though the maximum power factor in this system is about the same as the one for its ZPNR counterpart, the much smaller electronic thermal conductance of this phosphorene-based nanostructure can remarkably contribute to the improvement of the figure of merit. Also, we found that the symmetry/asymmetry of our designed nanostructures, the geometrical characteristics of the ring, and the magnetic flux are three important factors that control the thermoelectric properties of phosphorene quantum rings. Our numerical calculations show that by changing the magnetic flux through the nanoring, a drastic increase in the thermopower is observed near an antiresonance point. We demonstrate the tunability of the thermopower and the possibility to switch on and off the TE response of phosphorene nanorings with the magnetic flux. Moreover, for asymmetric connection configurations with armchair-edged leads, we found that though the thermopower is almost intact, a remarkable reduction of the electronic thermal

Published : "arXiv Mesoscale and Nanoscale Physics".

Electronic transport and thermoelectric properties of phosphorene nanodisk under an electric field. (arXiv:2212.09012v1 [cond-mat.mtrl-sci])

2022-12-20T02:29:41+00:00December 20th, 2022|Categories: Publications|Tags: , |

The Seebeck coefficient is an important quantity in determining the thermoelectric efficiency of a material. Phosphorene is a two-dimensional material with a puckered structure, which makes its properties anisotropic. In this work, a phosphorene nanodisk (PDisk) with a radius of 3.1 nm connected to two zigzag phosphorene nanoribbons is studied, numerically, by the tight-binding (TB) and non-equilibrium Greens function (NEGF) methods in the presence of transverse and perpendicular electric fields. Our results show that the change of the structure from a zigzag ribbon form to a disk one creates an energy gap in the structure, so that for a typical nanodisk with a radius of 3.1 nm, the size of the energy gap is 3.88 eV. Besides, with this change, the maximum Seebeck coefficient increases from 1.54 to 2.03 mV/K. Furthermore, we can control the electron transmission and Seebeck coefficients with the help of the electric fields. The numerical results show that with the increase of the electric field, the transmission coefficient decreases, and the Seebeck coefficient changes. The effect of a perpendicular electric field on the Seebeck coefficient is weaker than a transverse electric field. For an applied transverse electric field of 0.3 V/nm, the maximum Seebeck coefficient enhances to 2.09 mV/K.

Published in: "arXiv Material Science".

Quantum well confinement and competitive radiative pathways in the luminescence of black phosphorus layers. (arXiv:2212.01073v1 [cond-mat.mes-hall])

2022-12-05T02:29:31+00:00December 5th, 2022|Categories: Publications|Tags: , , |

Black phosphorus (BP) stands out from other 2D materials by the wide amplitude of the band-gap energy (Delta(Eg)) that sweeps an optical window from Visible (VIS) to Infrared (IR) wavelengths, depending on the layer thickness. This singularity made the optical and excitonic properties of BP difficult to map. Specifically, the literature lacks in presenting experimental and theoretical data on the optical properties of BP on an extended thickness range. Here we report the study of an ensemble of photoluminescence spectra from 79 passivated BP flakes recorded at 4 K with thicknesses ranging from 4 nm to 700 nm, obtained by mechanical exfoliation. We observe that the exfoliation steps induce additional defects states that compete the radiative recombination from bound excitons observed in the crystal. We also show that the evolution of the photoluminescence energy versus thickness follows a quantum well confinement model appreciable from a thickness predicted and probed at 25 nm. The BP slabs placed in different 2D heterostructures show that the emission energy is not significantly modulated by the dielectric environment. Introduction Confinement effects

Published in: "arXiv Material Science".

Synthesis of Fibrous Phosphorus Micropillar Arrays with Pyro‐Phototronic Effects

2022-12-02T13:08:15+00:00December 2nd, 2022|Categories: Publications|Tags: |

The bottom-up preparation of two-dimensional material micro-nano structures at scale facilitates the realisation of integrated applications in optoelectronic devices. Fibrous Phosphorus (FP), an allotrope of black phosphorus (BP), is one of the most promising candidate materials in the field of optoelectronics with its unique crystal structure and properties. However, to date, there are no bottom-up micro-nano structure preparation methods for crystalline phosphorus allotropes. Herein, we present the bottom-up preparation of fibrous phosphorus micropillar (FP-MP) arrays via a low-pressure gas-phase transport (LP-CVT) method that controls the directional phase transition from amorphous red phosphorus (ARP) to FP. In addition, self-powered photodetectors (PD) of FP-MP arrays with pyro-phototronic effects achieved detection beyond the bandgap limit. Our results provide a new approach for bottom-up preparation of other crystalline allotropes of phosphorus.

Published in: "Angewandte Chemie International Edition".

Colossal shift current response in elemental two-dimensional ferroelectrics. (arXiv:2212.00326v1 [cond-mat.mtrl-sci])

2022-12-02T02:29:22+00:00December 2nd, 2022|Categories: Publications|Tags: |

A bulk material without inversion symmetry can generate a direct current under uniform illumination. This interface-free current generation mechanism, referred to as the bulk photovoltaic effect (BPVE), has the potential to overcome the Shockley-Queisser limit of traditional solar cells based on $p$-$n$ junctions. Here, we explore the shift current generation, a major mechanism responsible for the BPVE, in single-element two-dimensional ferroelectrics represented by phosphorene-like monolayers of As, Sb, and Bi. The strong covalency and large joint density of states afforded by these elemental 2D materials give rise to colossal shift currents, outperforming many state-of-the-art materials over a wide range of wavelengths including the visible light spectrum. For a given frequency and polarization of an incoming light, we find that the shift current, due to its topological nature, depends sensitively on the details of the Bloch wave functions. It is crucial to consider the electronic exchange-correlation potential beyond the generalized gradient approximation as well as the spin-orbit interaction in density functional theory calculations to obtain reliable photon frequency-dependent shift current responses.

Published in: "arXiv Material Science".

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