1
|
Ren K, Liu JZ, Palummo M, Sun M. Editorial: Theoretical study of two-dimensional materials for photocatalysis and photovoltaics. Front Chem 2024; 12:1387236. [PMID: 38510812 PMCID: PMC10951059 DOI: 10.3389/fchem.2024.1387236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Accepted: 02/20/2024] [Indexed: 03/22/2024] Open
Affiliation(s)
- Kai Ren
- School of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing, China
| | - Jefferson Zhe Liu
- Department of Mechanical Engineering, The University of Melbourne, Parkville, VIC, Australia
| | - Maurizia Palummo
- Dipartimento di Fisica and INFN, Università di Roma ‟Tor Vergata”, Roma, Italy
| | - Minglei Sun
- Department of Physics and NANOlab Center of Excellence, University of Antwerp, Antwerp, Belgium
| |
Collapse
|
2
|
Wu F, Tan H, Palummo M, Camilli L. Mechanical properties of bilayer WS 2and Graphene-WS 2Hybrid composites by molecular dynamics simulations. J Phys Condens Matter 2024; 36:225301. [PMID: 38346347 DOI: 10.1088/1361-648x/ad2886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 02/12/2024] [Indexed: 03/06/2024]
Abstract
In the present work, by using molecular dynamics (MD) simulations, we investigate the mechanical properties of different nanostructures that may be core elements in next generation flexible/wearable photovoltaic devices, namely double layer WS2nanosheets (DLNS), graphene/WS2(layer) composites and graphene/WS2nanotube (NT) composites. Our results reveal that the mechanical properties of DLNS deteriorate when compared to those of monolayer WS2. Owing to graphene's reinforcement action, the mechanical properties of graphene/WS2(layer) composite with both layers deformed are superior than those of WS2, even though inferior than those of bare graphene. If stress is applied only to the graphene layer, the graphene/WS2composite retains the most of the strength and toughness of monolayer graphene, decreasing the fracture strength and Young's modulus by only 9.7% and 16.3%, respectively. Similarly, in the case of the graphene/WS2NT composite the mechanical strength and toughness experience a reduction compared to monolayer graphene, specifically by 15% and 53% for fracture strength and Young's modulus, respectively. Considering the market's keen interest in nanomaterials, particularly van der Waals (vdW) ones, for flexible and wearable photovoltaic devices, the findings presented here will significantly enhance the effective utilization of vdW composites.
Collapse
Affiliation(s)
- Fan Wu
- Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, People's Republic of China
- Dipartimento di Fisica, Università degli studi di Roma Tor Vergata, via della Ricerca Scientifica 1, Rome, 00133, Italy
| | - Huifeng Tan
- Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, People's Republic of China
| | - Maurizia Palummo
- Dipartimento di Fisica, Università degli studi di Roma Tor Vergata, via della Ricerca Scientifica 1, Rome, 00133, Italy
| | - Luca Camilli
- Dipartimento di Fisica, Università degli studi di Roma Tor Vergata, via della Ricerca Scientifica 1, Rome, 00133, Italy
| |
Collapse
|
3
|
Folpini G, Palummo M, Cortecchia D, Moretti L, Cerullo G, Petrozza A, Giorgi G, Srimath Kandada AR. Plurality of excitons in Ruddlesden-Popper metal halides and the role of the B-site metal cation. Mater Adv 2023; 4:1720-1730. [PMID: 37026040 PMCID: PMC10068426 DOI: 10.1039/d2ma00136e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 03/06/2023] [Indexed: 06/19/2023]
Abstract
We investigate the effect of metal cation substition on the excitonic structure and dynamics in a prototypical Ruddlesden-Popper metal halide. Through an in-depth spectroscopic and theoretical analysis, we identify the presence of multiple resonances in the optical spectra of a phenethyl ammonium tin iodide, a tin-based RPMH. Based on ab initio calculations, we assign these resonances to distinct exciton series that originate from the splitting of the conduction band due to spin-orbit coupling. While the splitting energy in the tin based system is low enough to enable the observation of the higher lying exciton in the visible-range spectrum of the material, the higher splitting energy in the lead counterpart prevents the emergence of such a feature. We elucidate the critical role played by the higher lying excitonic state in the ultrafast carrier thermalization dynamics.
Collapse
Affiliation(s)
- Giulia Folpini
- CNST@Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3 Milano Italy
| | - Maurizia Palummo
- Dipartimento di Fisica and INFN, Universitá di Roma "Tor Vergata", Via della Ricerca Scientifica 1 Roma Italy
| | - Daniele Cortecchia
- CNST@Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3 Milano Italy
| | - Luca Moretti
- Dipartimento di Fisica, Politecnico di Milano Milano Italy
| | - Giulio Cerullo
- Dipartimento di Fisica, Politecnico di Milano Milano Italy
| | - Annamaria Petrozza
- CNST@Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3 Milano Italy
| | - Giacomo Giorgi
- Department of Civil and Environmental Engineering (DICA), University of Perugia, Via G. Duranti, 93 06125 Perugia Italy
- CNR-SCITEC I-06123 Perugia Italy
- CIRIAF - Interuniversity Research Centre, University of Perugia, Via G. Duranti 93 06125 Perugia Italy
| | - Ajay Ram Srimath Kandada
- Department of Physics and Center for Functional Materials 1834 Wake Forest Road Winston-Salem NC 27109 USA
| |
Collapse
|
4
|
Palummo M, Re Fiorentin M, Yamashita K, Castelli IE, Giorgi G. Study of Optoelectronic Features in Polar and Nonpolar Polymorphs of the Oxynitride Tin-Based Semiconductor InSnO 2N. J Phys Chem Lett 2023; 14:1548-1555. [PMID: 36745501 PMCID: PMC9940202 DOI: 10.1021/acs.jpclett.3c00211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/02/2023] [Indexed: 06/18/2023]
Abstract
In view of its potential applicability in photoconversion processes, we here discuss the optoelectronic features of the recently proposed tin-based oxynitride material for (photo)catalysis, InSnO2N. In detail, by combining Density Functional and Many-Body Perturbation Theory, we compute the electronic and optical properties discussing how they vary from the nonpolar phase to the more stable polar one. After providing a detailed, unbiased, description of the optoelectronic features of the two phases, we have finally calculated the Spectroscopic Limited Maximum Efficiency and obtained data that further witness the relevance of InSnO2N for solar energy conversion processes.
Collapse
Affiliation(s)
- Maurizia Palummo
- Department
of Physics & INFN, Universitá
di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Michele Re Fiorentin
- Department
of Applied Science and Technology, Politecnico
di Torino, corso Duca
degli Abruzzi 24, 10129 Torino, Italy
| | - Koichi Yamashita
- Graduate
School of Nanobioscience, Yokohama City
University, Yokohama 236-0027, Japan
| | - Ivano E. Castelli
- Department
of Energy Conversion and Storage, Technical
University of Denmark, DK-2800
Kgs. Lyngby, Denmark
| | - Giacomo Giorgi
- Department
of Civil & Environmental Engineering (DICA), The University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy
- CIRIAF
- Interuniversity Research Centre, University
of Perugia, Via G. Duranti
93, 06125 Perugia, Italy
- CNR-SCITEC, 06123 Perugia, Italy
| |
Collapse
|
5
|
Attaccalite C, Prete MS, Palummo M, Pulci O. Interlayer and Intralayer Excitons in AlN/ WS2 Heterostructure. Materials (Basel) 2022; 15:8318. [PMID: 36499811 PMCID: PMC9735989 DOI: 10.3390/ma15238318] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 06/17/2023]
Abstract
The study of intra and interlayer excitons in 2D semiconducting vdW heterostructures is a very hot topic not only from a fundamental but also an applicative point of view. Due to their strong light-matter interaction, Transition Metal Dichalcogenides (TMD) and group-III nitrides are particularly attractive in the field of opto-electronic applications such as photo-catalytic and photo-voltaic ultra-thin and flexible devices. Using first-principles ground and excited-state simulations, we investigate here the electronic and excitonic properties of a representative nitride/TMD heterobilayer, the AlN/WS2. We demonstrate that the band alignment is of type I, and low energy intralayer excitons are similar to those of a pristine WS2 monolayer. Further, we disentangle the role of strain and AlN dielectric screening on the electronic and optical gaps. These results, although they do not favor the possible use of AlN/WS2 in photo-catalysis, as envisaged in the previous literature, can boost the recently started experimental studies of 2D hexagonal aluminum nitride as a good low screening substrate for TMD-based electronic and opto-electronic devices. Importantly, our work shows how the inclusion of both spin-orbit and many-body interactions is compulsory for the correct prediction of the electronic and optical properties of TMD/nitride heterobilayers.
Collapse
Affiliation(s)
- Claudio Attaccalite
- Centre Interdisciplinaire de Nanoscience de Marseille UMR 7325 Campus de Luminy, CNRS/Aix-Marseille Université, CEDEX 9, 13288 Marseille, France
- European Theoretical Spectroscopy Facilities (ETSF)
| | - Maria Stella Prete
- Dipartimento di Fisica, Universitá di Roma Tor Vergata, and INFN, Via della Ricerca Scientifica 1, I-00133 Rome, Italy
| | - Maurizia Palummo
- European Theoretical Spectroscopy Facilities (ETSF)
- Dipartimento di Fisica, Universitá di Roma Tor Vergata, and INFN, Via della Ricerca Scientifica 1, I-00133 Rome, Italy
| | - Olivia Pulci
- European Theoretical Spectroscopy Facilities (ETSF)
- Dipartimento di Fisica, Universitá di Roma Tor Vergata, and INFN, Via della Ricerca Scientifica 1, I-00133 Rome, Italy
| |
Collapse
|
6
|
Costantini R, Cilento F, Salvador F, Morgante A, Giorgi G, Palummo M, Dell’Angela M. Photo-induced lattice distortion in 2H-MoTe2 probed by time-resolved core level photoemission. Faraday Discuss 2022; 236:429-441. [DOI: 10.1039/d1fd00105a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The technological interest in MoTe2 as a phase engineered material is related to the possibility of triggering the 2H-1T’ phase transition by optical excitation, potentially allowing for an accurate patterning...
Collapse
|
7
|
Bastonero L, Cicero G, Palummo M, Re Fiorentin M. Boosted Solar Light Absorbance in PdS 2/PtS 2 Vertical Heterostructures for Ultrathin Photovoltaic Devices. ACS Appl Mater Interfaces 2021; 13:43615-43621. [PMID: 34468121 PMCID: PMC8447185 DOI: 10.1021/acsami.1c11245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 07/29/2021] [Indexed: 06/13/2023]
Abstract
Transition-metal dichalcogenides (TMDs) represent a class of materials whose archetypes, such as MoS2 and WS2, possess exceptional electronic and optical properties and have been massively exploited in optoelectronic applications. The layered structure allows for their exfoliation to two-dimensional samples with atomic thickness (≲ 1 nm), promising for ultrathin, ultralight devices. In this work, by means of state-of-the-art ab initio many-body perturbation theory techniques, we focus on single-layer PdS2 and PtS2 and propose a novel van der Waals heterostructure with outstanding light absorbance, reaching up to 50% in the visible spectrum and yielding a maximum short-circuit current of 7.2 mA/cm2 under solar irradiation. The computed excitonic landscape predicts a partial charge separation between the two layers and the momentum-forbidden lowest-energy state increases the carrier diffusion length. Our results show that the employment of vertical heterostructures with less conventional TMDs, such as PdS2/PtS2, can greatly boost light absorbance and favor the development of more efficient, atomic-thin photovoltaic devices.
Collapse
Affiliation(s)
- Lorenzo Bastonero
- U
Bremen Excellence Chair “Materials Design and Discovery”
and Hybrid Materials Interfaces Group, Bremen Center for Computational
Materials Science, University of Bremen, Am Fallturm 1, 28359 Bremen, Germany
- Dipartimento
di Fisica, Università Degli Studi
Torino, Via Giuria 1, 10125 Torino, Italy
| | - Giancarlo Cicero
- Dipartimento
di Scienza Applicata e Tecnologia, Politecnico
di Torino, Corso Duca Degli Abruzzi 24, 10129 Torino, Italy
| | - Maurizia Palummo
- Dipartimento
di Fisica and INFN, Università di
Roma “Tor Vergata”, Via Della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Michele Re Fiorentin
- Center
for Sustainable Future Technologies, Istituto
Italiano di Tecnologia, Via Livorno 60, 10144 Torino, Italy
| |
Collapse
|
8
|
Palummo M, Raimondo L, Hogan C, Goletti C, Trabattoni S, Sassella A. Nature of Optical Excitations in Porphyrin Crystals: A Joint Experimental and Theoretical Study. J Phys Chem Lett 2021; 12:869-875. [PMID: 33428409 PMCID: PMC8023704 DOI: 10.1021/acs.jpclett.0c03581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
The nature of optical excitations and the spatial extent of excitons in organic semiconductors, both of which determine exciton diffusion and carrier mobilities, are key factors for the proper understanding and tuning of material performances. Using a combined experimental and theoretical approach, we investigate the excitonic properties of meso-tetraphenyl porphyrin-Zn(II) crystals. We find that several bands contribute to the optical absorption spectra, beyond the four main ones considered here as the analogue to the four frontier molecular orbitals of the Gouterman model commonly adopted for the isolated molecule. By using many-body perturbation theory in the GW and Bethe-Salpeter equation approach, we interpret the experimental large optical anisotropy as being due to the interplay between long- and short-range intermolecular interactions. In addition, both localized and delocalized excitons in the π-stacking direction are demonstrated to determine the optical response, in agreement with recent experimental observations reported for organic crystals with similar molecular packing.
Collapse
Affiliation(s)
- Maurizia Palummo
- INFN,
Dipartimento di Fisica, Università
di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma, Italy
| | - Luisa Raimondo
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, Via Roberto Cozzi 55, I-20125 Milano, Italy
| | - Conor Hogan
- Istituto
di Struttura della Materia-CNR (ISM-CNR), Via del Fosso del Cavaliere 100, I-00133 Roma, Italy
- Dipartimento
di Fisica, Università di Roma Tor
Vergata, Via della Ricerca
Scientifica 1, I-00133 Roma, Italy
| | - Claudio Goletti
- Dipartimento
di Fisica, Università di Roma Tor
Vergata, Via della Ricerca
Scientifica 1, I-00133 Roma, Italy
| | - Silvia Trabattoni
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, Via Roberto Cozzi 55, I-20125 Milano, Italy
| | - Adele Sassella
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, Via Roberto Cozzi 55, I-20125 Milano, Italy
| |
Collapse
|
9
|
Postorino S, Sun J, Fiedler S, Lee Cheong Lem LO, Palummo M, Camilli L. Interlayer Bound Wannier Excitons in Germanium Sulfide. Materials (Basel) 2020; 13:ma13163568. [PMID: 32806742 PMCID: PMC7475894 DOI: 10.3390/ma13163568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 08/04/2020] [Accepted: 08/07/2020] [Indexed: 05/05/2023]
Abstract
We report a cathodoluminescence (CL) study of layered germanium sulfide (GeS) where we observe a sharp emission peak from flakes covered with a thin hexagonal boron nitride film. GeS is a material that has recently attracted considerable interest due to its emission in the visible region and its strong anisotropy. The measured CL peak is at ~1.69 eV for samples ranging in thickness from 97 nm to 45 nm, where quantum-confinement effects can be excluded. By performing ab initio ground- and excited-state simulations for the bulk compound, we show that the measured optical peak can be unambiguously explained by radiative recombination of the first free bright bound exciton, which is due to a mixing of direct transitions near the Γ-point of the Brillouin Zone and it is associated to a very large optical anisotropy. The analysis of the corresponding excitonic wave function shows a Wannier-Mott interlayer character, being spread not only in-plane but also out-of-plane.
Collapse
Affiliation(s)
- Sara Postorino
- Dipartimento di Fisica, Università degli studi di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy;
| | - Jianbo Sun
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark;
| | - Saskia Fiedler
- Centre for Nano Optics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark;
| | - Laurent O. Lee Cheong Lem
- Australian National Fabrication Facility, Australian National University, Canberra 2601, ACT, Australia;
| | - Maurizia Palummo
- Dipartimento di Fisica, Università degli studi di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy;
- Istituto Nazionale di Fisica Nucleare, via della Ricerca Scientifica 1, 00133 Roma, Italy
- Correspondence: (M.P.); (L.C.)
| | - Luca Camilli
- Dipartimento di Fisica, Università degli studi di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy;
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark;
- Correspondence: (M.P.); (L.C.)
| |
Collapse
|
10
|
Varsano D, Palummo M, Molinari E, Rontani M. A monolayer transition-metal dichalcogenide as a topological excitonic insulator. Nat Nanotechnol 2020; 15:367-372. [PMID: 32123382 DOI: 10.1038/s41565-020-0650-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
Monolayer transition-metal dichalcogenides in the T' phase could enable the realization of the quantum spin Hall effect1 at room temperature, because they exhibit a prominent spin-orbit gap between inverted bands in the bulk2,3. Here we show that the binding energy of electron-hole pairs excited through this gap is larger than the gap itself in the paradigmatic case of monolayer T' MoS2, which we investigate from first principles using many-body perturbation theory4. This paradoxical result hints at the instability of the T' phase in the presence of spontaneous generation of excitons, and we predict that it will give rise to a reconstructed 'excitonic insulator' ground state5-7. Importantly, we show that in this monolayer system, topological and excitonic order cooperatively enhance the bulk gap by breaking the crystal inversion symmetry, in contrast to the case of bilayers8-16 where the frustration between the two orders is relieved by breaking time reversal symmetry13,15,16. The excitonic topological insulator is distinct from the bare topological phase because it lifts the band spin degeneracy, which results in circular dichroism. A moderate biaxial strain applied to the system leads to two additional excitonic phases, different in their topological character but both ferroelectric17,18 as an effect of electron-electron interaction.
Collapse
Affiliation(s)
| | - Maurizia Palummo
- INFN, Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, Roma, Italy
| | - Elisa Molinari
- CNR-NANO, Modena, Italy
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università degli Studi di Modena e Reggio Emilia, Modena, Italy
| | | |
Collapse
|
11
|
Sun J, Giorgi G, Palummo M, Sutter P, Passacantando M, Camilli L. A Scalable Method for Thickness and Lateral Engineering of 2D Materials. ACS Nano 2020; 14:4861-4870. [PMID: 32155048 DOI: 10.1021/acsnano.0c00836] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The physical properties of two-dimensional (2D) materials depend strongly on the number of layers. Hence, methods for controlling their thickness with atomic layer precision are highly desirable, yet still too rare, and demonstrated for only a limited number of 2D materials. Here, we present a simple and scalable method for the continuous layer-by-layer thinning that works for a large class of 2D materials, notably layered germanium pnictides and chalcogenides. It is based on a simple oxidation/etching process, which selectively occurs on the topmost layers. Through a combination of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction experiments we demonstrate the thinning method on germanium arsenide (GeAs), germanium sulfide (GeS), and germanium disulfide (GeS2). We use first-principles simulation to provide insights into the oxidation mechanism. Our strategy, which could be applied to other classes of 2D materials upon proper choice of the oxidation/etching reagent, supports 2D material-based device applications, e.g., in electronics or optoelectronics, where a precise control over the number of layers (hence over the material's physical properties) is needed. Finally, we also show that when used in combination with lithography, our method can be used to make precise patterns in the 2D materials.
Collapse
Affiliation(s)
- Jianbo Sun
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark
| | - Giacomo Giorgi
- Dipartimento di Ingegneria Civile ed Ambientale, Università degli Studi di Perugia, via G. Duranti 93, 06125 Perugia, Italy
- Istituto di Scienze e Tecnologie Chimiche "Giulio Natta″, Consiglio Nazionale delle Ricerche, via Elce di Sotto 8, 06123 Perugia, Italy
| | - Maurizia Palummo
- Dipartimento di Fisica, Università degli studi di Roma "Tor Vergata", via della Ricerca Scientifica 1, 00133 Roma, Italy
- Istituto Nazionale di Fisica Nucleare, via della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, 1400 R St, Lincoln, Nebraska 68588, United States
| | - Maurizio Passacantando
- Department of Physical and Chemical Science, University of L'Aquila, via Vetoio, 67100 L'Aquila, Italy
- SuPerconducting and Other INnovative Materials and Devices Institute (SPIN), Department of Physical Sciences and Technologies of Matter, Consiglio Nazionale delle Ricerche, via Vetoio, 67100 L'Aquila, Italy
| | - Luca Camilli
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark
- Dipartimento di Fisica, Università degli studi di Roma "Tor Vergata", via della Ricerca Scientifica 1, 00133 Roma, Italy
| |
Collapse
|
12
|
Jhalani VA, Chen HY, Palummo M, Bernardi M. Precise radiative lifetimes in bulk crystals from first principles: the case of wurtzite gallium nitride. J Phys Condens Matter 2020; 32:084001. [PMID: 31698340 DOI: 10.1088/1361-648x/ab5563] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Gallium nitride (GaN) is a key semiconductor for solid-state lighting, but its radiative processes are not fully understood. Here we show a first-principles approach to accurately compute the radiative lifetimes in bulk uniaxial crystals, focusing on wurtzite GaN. Our computed radiative lifetimes are in very good agreement with experiment up to 100 K. We show that taking into account excitons (through the Bethe-Salpeter equation) and spin-orbit coupling is essential for computing accurate radiative lifetimes. A model for exciton dissociation into free carriers allows us to compute the radiative lifetimes up to room temperature. Our work enables precise radiative lifetime calculations in III-nitrides and other anisotropic solid-state emitters.
Collapse
Affiliation(s)
- Vatsal A Jhalani
- Department of Applied Physics and Materials Science, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, United States of America
| | | | | | | |
Collapse
|
13
|
Ossicini S, Marri I, Amato M, Palummo M, Canadell E, Rurali R. Ab initio studies of the optoelectronic structure of undoped and doped silicon nanocrystals and nanowires: the role of size, passivation, symmetry and phase. Faraday Discuss 2020; 222:217-239. [DOI: 10.1039/c9fd00085b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Results from ab initio calculations for singly- and co- doped Si nanocrystals and nanowires are presented.
Collapse
Affiliation(s)
- Stefano Ossicini
- Dipartimento di Scienze e Metodi Dell’Ingegneria
- Centro Interdipartimentale En&Tech
- Universitá di Modena e Reggio Emilia
- I-42125 Reggio Emilia
- Italy
| | - Ivan Marri
- Centro S3
- CNR-Istituto di Nanoscienze
- I-41125 Modena
- Italy
| | - Michele Amato
- Laboratoire de Physique des Solides (LPS)
- CNRS
- Université Paris Sud
- Université Paris-Saclay
- Centre Scientifique D’Orsay
| | - Maurizia Palummo
- Dipartimento di Fisica and INFN
- Universitá di Roma Tor Vergata
- 00133 Roma
- Italy
| | - Enric Canadell
- Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC)
- Campus de Bellaterra
- Barcelona
- Spain
| | - Riccardo Rurali
- Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC)
- Campus de Bellaterra
- Barcelona
- Spain
| |
Collapse
|
14
|
Sangalli D, Ferretti A, Miranda H, Attaccalite C, Marri I, Cannuccia E, Melo P, Marsili M, Paleari F, Marrazzo A, Prandini G, Bonfà P, Atambo MO, Affinito F, Palummo M, Molina-Sánchez A, Hogan C, Grüning M, Varsano D, Marini A. Many-body perturbation theory calculations using the yambo code. J Phys Condens Matter 2019; 31:325902. [PMID: 30943462 DOI: 10.1088/1361-648x/ab15d0] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
yambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as Quantum ESPRESSO and Abinit. yambo's capabilities include the calculation of linear response quantities (both independent-particle and including electron-hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron-phonon interactions to the implementation of a real-time propagation scheme for simulating linear and non-linear optical properties. Improvements to numerical algorithms and the user interface are outlined. Particular emphasis is given to the new and efficient parallel structure that makes it possible to exploit modern high performance computing architectures. Finally, we demonstrate the possibility to automate workflows by interfacing with the yambopy and AiiDA software tools.
Collapse
Affiliation(s)
- D Sangalli
- Istituto di Struttura della Materia-Consiglio Nazionale delle Ricerche (CNR-ISM), Division of Ultrafast Processes in Materials (FLASHit), Via Salaria Km 29.5, CP 10, I-00016 Monterotondo Stazione, Italy. European Theoretical Spectroscopy Facility (ETSF
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Perfetto E, Sangalli D, Palummo M, Marini A, Stefanucci G. First-Principles Nonequilibrium Green’s Function Approach to Ultrafast Charge Migration in Glycine. J Chem Theory Comput 2019; 15:4526-4534. [DOI: 10.1021/acs.jctc.9b00170] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- E. Perfetto
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma 1, Via Salaria Km 29.3, I-00016 Monterotondo Scalo, Italy
| | - D. Sangalli
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma 1, Via Salaria Km 29.3, I-00016 Monterotondo Scalo, Italy
| | - M. Palummo
- Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
| | - A. Marini
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma 1, Via Salaria Km 29.3, I-00016 Monterotondo Scalo, Italy
| | - G. Stefanucci
- Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
- INFN, Sezione di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
| |
Collapse
|
16
|
Palummo M, D'Auria AN, Grossman JC, Cicero G. Tailoring the optical properties of MoS 2 and WS 2 single layers via organic functionalization. J Phys Condens Matter 2019; 31:235701. [PMID: 30831563 DOI: 10.1088/1361-648x/ab0c5e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Tailoring the structural and electronic properties of 2D materials is fundamental to boost their use in a wide range of technological applications. In this paper, by means of first principles simulations, we show how methyl functionalization of MoS2 and WS2 monolayers can be employed to change their energy gap, tune their optoelectronic properties and modify the relative stability of their structural phases (or polytypes). In particular for both compound monolayers, we find that the most stable semiconducting H phase becomes metallic upon methyl functionalization, while in the metastable T' phase the band gap increases as a function of the -CH3 coverage; correspondingly the phase stability is reversed and the on-set of the optical absorption is blue-shifted.
Collapse
Affiliation(s)
- M Palummo
- Dipartimento di Fisica, Università di Roma Tor Vergata and INFN, Via della Ricerca Scientifica 1, 00133 Roma, Italy
| | | | | | | |
Collapse
|
17
|
Giorgi G, Yamashita K, Palummo M. Nature of the Electronic and Optical Excitations of Ruddlesden-Popper Hybrid Organic-Inorganic Perovskites: The Role of the Many-Body Interactions. J Phys Chem Lett 2018; 9:5891-5896. [PMID: 30244580 DOI: 10.1021/acs.jpclett.8b02653] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The knowledge of the exact nature of the electronic and optical excitations of Ruddlesden-Popper organic-inorganic halide perovskites (RPPs) is particularly relevant in view of their usage in optoelectronic devices. By means of parameter-free quantum-mechanical simulations, we unambiguously demonstrate the dominant role of many-body Coulomb interaction, as recently proposed by Blancon et al. Indeed, focusing on the first two terms ( n = 1,2) of the Pb-based buthylammonium series, in the form of both isolated nanosheet and repeated bulk-like quantum well, we observe large band gap renormalization and strongly bound excitons with binding energies up to ∼1 eV in the thinnest isolated nanosheet. Notably, taking into account electronic correlation beyond density functional theory, we obtain exciton reduced masses similar to the corresponding 3D bulk counterpart and large Rashba splitting of the same order of the value reported by Zhai et al. in a recent experimental work.
Collapse
Affiliation(s)
- Giacomo Giorgi
- Dipartimento di Ingegneria Civile e Ambientale , Universitá di Perugia (DICA) , Via G. Duranti, 93 , 06125 Perugia , Italy
| | - Koichi Yamashita
- Department of Chemical System Engineering, School of Engineering , The University of Tokyo , 13-8656 Tokyo , Japan
- CREST-JST , 102-0076 Tokyo , Japan
| | - Maurizia Palummo
- Dipartimento di Fisica and INFN , Universitá di Roma "Tor Vergata" , Via della Ricerca Scientifica 1 , 00133 Roma , Italy
| |
Collapse
|
18
|
Chen HY, Palummo M, Sangalli D, Bernardi M. Theory and Ab Initio Computation of the Anisotropic Light Emission in Monolayer Transition Metal Dichalcogenides. Nano Lett 2018; 18:3839-3843. [PMID: 29737164 DOI: 10.1021/acs.nanolett.8b01114] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Monolayer transition metal dichalcogenides (TMDCs) are direct gap semiconductors with a unique potential for use in ultrathin light emitters. However, their photoluminescence (PL) is not completely understood. We develop an approach to compute the radiative recombination rate in monolayer TMDCs as a function of photon emission direction and polarization. Using exciton wavefunctions and energies obtained with the ab initio Bethe-Salpeter equation, we obtain polar plots of the PL for different scenarios. Our results can explain the PL anisotropy and polarization dependence measured in recent experiments and predict that light is emitted with a peak intensity normal to the exciton dipole in monolayer TMDCs. We show that excitons emit light anisotropically upon recombination when they are in any quantum superposition state of the K and K' inequivalent valleys. When averaged over the emission angle and exciton momentum, our new treatment recovers the temperature-dependent radiative lifetimes that we previously derived. Our work demonstrates a generally applicable first-principles approach to studying anisotropic light emission in two-dimensional materials.
Collapse
Affiliation(s)
| | - Maurizia Palummo
- Dipartimento di Fisica and INFN , Università di Roma Tor Vergata , Via della Ricerca Scientifica 1 , 00133 Roma , Italy
| | - Davide Sangalli
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) , Area della Ricerca di Roma 1 , 00016 Monterotondo Scalo , Italy
| | | |
Collapse
|
19
|
Abstract
Despite most of the applications of anatase nanostructures rely on photoexcited charge processes, yet profound theoretical understanding of fundamental related properties is lacking. Here, by means of ab initio ground and excited-state calculations, we reveal, in an unambiguous way, the role of quantum confinement effect and of the surface orientation, on the electronic and optical properties of anatase nanosheets (NSs). The presence of bound excitons extremely localized along the (001) direction, whose existence has been recently proven also in anatase bulk, explains the different optical behavior found for the two orientations - (001) and (101) - when the NS thickness increases. We suggest also that the almost two-dimensional nature of these excitons can be related to the improved photoconversion efficiency observed when a high percentage of (001) facet is present in anatase nanocrystals.
Collapse
Affiliation(s)
- Daniele Varsano
- Center S3, CNR Institute of Nanoscience, Via Campi 213/A, 41125 Modena, Italy
| | - Giacomo Giorgi
- Dipartimento di Ingegneria Civile e Ambientale, Universitá di Perugia (DICA) , Via G. Duranti, 93, 06125 Perugia, Italy
| | - Koichi Yamashita
- Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Maurizia Palummo
- Dipartimento di Fisica and INFN, Universitá di Roma "Tor Vergata" Via della Ricerca Scientifica 1, 00173 Roma, Italy
| |
Collapse
|
20
|
Abstract
Recent advances in the synthetic growth of nanowires have given access to crystal phases that in bulk are only observed under extreme pressure conditions. Here, we use first-principles methods based on density functional theory and many-body perturbation theory to show that a suitable mixing of hexagonal Si and hexagonal Ge yields a direct bandgap with an optically permitted transition. Comparison of the calculated radiative lifetimes with typical values of nonradiative recombination mechanisms indicates that optical emission will be the dominant recombination mechanism. These findings pave the way to the development of silicon-based optoelectronic devices, thus far hindered by the poor light emission efficiency of cubic Si.
Collapse
Affiliation(s)
- Xavier Cartoixà
- Departament d'Enginyeria Electrònica, Universitat Autònoma de Barcelona , 08193 Bellaterra, Barcelona, Spain
| | - Maurizia Palummo
- Dipartimento di Fisica and INFN, Università di Roma "Tor Vergata" via della Ricerca Scientifica 1 , 00133 Roma, Italy
| | - Håkon Ikaros T Hauge
- Department of Applied Physics, TU Eindhoven , Den Dolech 2, 5612 AZ Eindhoven, The Netherlands
| | - Erik P A M Bakkers
- Department of Applied Physics, TU Eindhoven , Den Dolech 2, 5612 AZ Eindhoven, The Netherlands
| | - Riccardo Rurali
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de Bellaterra , 08193 Bellaterra, Barcelona, Spain
| |
Collapse
|
21
|
Abstract
Recent experimental investigations have confirmed the possibility to synthesize and exploit polytypism in group IV nanowires. Driven by this promising evidence, we use first-principles methods based on density functional theory and many-body perturbation theory to investigate the electronic and optical properties of hexagonal-diamond and cubic-diamond Si NWs as well as their homojunctions. We show that hexagonal-diamond NWs are characterized by a more pronounced quantum confinement effect than cubic-diamond NWs. Furthermore, they absorb more light in the visible region with respect to cubic-diamond ones and, for most of the studied diameters, they are direct band gap materials. The study of the homojunctions reveals that the diameter has a crucial effect on the band alignment at the interface. In particular, at small diameters the band-offset is type-I whereas at experimentally relevant sizes the offset turns up to be of type-II. These findings highlight intriguing possibilities to modulate electron and hole separations as well as electronic and optical properties by simply modifying the crystal phase and the size of the junction.
Collapse
Affiliation(s)
| | | | | | - Maurizia Palummo
- Dipartimento di Fisica, Università di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Roma, Italy
- INFN, Laboratori Nazionali di Frascati, Via E. Fermi 40, I-00044 Frascati, Italy
| | - Riccardo Rurali
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de Bellaterra , 08193 Bellaterra, Barcelona, Spain
| |
Collapse
|
22
|
Abstract
Light emission in two-dimensional (2D) transition metal dichalcogenides (TMDs) changes significantly with the number of layers and stacking sequence. While the electronic structure and optical absorption are well understood in 2D-TMDs, much less is known about exciton dynamics and radiative recombination. Here, we show first-principles calculations of intrinsic exciton radiative lifetimes at low temperature (4 K) and room temperature (300 K) in TMD monolayers with the chemical formula MX2 (X = Mo, W, and X = S, Se), as well as in bilayer and bulk MoS2 and in two MX2 heterobilayers. Our results elucidate the time scale and microscopic origin of light emission in TMDs. We find radiative lifetimes of a few picoseconds at low temperature and a few nanoseconds at room temperature in the monolayers and slower radiative recombination in bulk and bilayer than in monolayer MoS2. The MoS2/WS2 and MoSe2/WSe2 heterobilayers exhibit very long-lived (∼20-30 ns at room temperature) interlayer excitons constituted by electrons localized on the Mo-based and holes on the W-based monolayer. The wide radiative lifetime tunability, together with the ability shown here to predict radiative lifetimes from computations, hold unique potential to manipulate excitons in TMDs and their heterostructures for application in optoelectronics and solar energy conversion.
Collapse
Affiliation(s)
- Maurizia Palummo
- †Dipartimento di Fisica, Università di Roma Tor Vergata, and European Theoretical Spectroscopy Facility (ETSF), Via della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Marco Bernardi
- ‡Department of Physics, University of California, Berkeley, California 94720, United States
| | - Jeffrey C Grossman
- §Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States
| |
Collapse
|
23
|
Abstract
By means of parameter-free quantum-mechanical dielectric response calculations of thin Si and Ge nanowires we explain the presence of the low energy peaks observed in EELS-TEM experiments and predict an important nanowire diameter dependence of the volume plasmon peak due to quantum-confinement effects, which is consistent with the blue shift observed experimentally in thicker wires.
Collapse
Affiliation(s)
- Maurizia Palummo
- Dipartimento di Fisica e European Theoretical Spectroscopy Facility (ETSF)
- Universitá degli Studi di Roma “Tor Vergata”
- 00133 Roma
- Italy
- INFN
| | - Conor Hogan
- Dipartimento di Fisica e European Theoretical Spectroscopy Facility (ETSF)
- Universitá degli Studi di Roma “Tor Vergata”
- 00133 Roma
- Italy
- Istituto di Struttura della Materia
| | - Stefano Ossicini
- Dipartimento di Scienze e Metodi dell'Ingegneria
- Universitá di Modena e Reggio Emilia
- I-42100 Reggio Emilia
- Italy
| |
Collapse
|
24
|
Demján T, Vörös M, Palummo M, Gali A. Electronic and optical properties of pure and modified diamondoids studied by many-body perturbation theory and time-dependent density functional theory. J Chem Phys 2014; 141:064308. [DOI: 10.1063/1.4891930] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
|
25
|
Amato M, Palummo M, Rurali R, Ossicini S. Silicon–Germanium Nanowires: Chemistry and Physics in Play, from Basic Principles to Advanced Applications. Chem Rev 2013; 114:1371-412. [DOI: 10.1021/cr400261y] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Michele Amato
- Institut d’Electronique Fondamentale, UMR8622, CNRS, Université Paris-Sud, 91405 Orsay, France
| | - Maurizia Palummo
- European
Theoretical Spectroscopy Facility (ETSF), Dipartimento di Fisica, Università di Roma, “Tor Vergata”, Via della Ricerca
Scientifica 1, 00133 Roma, Italy
| | - Riccardo Rurali
- Institut de Ciència de Materials de Barcelona (ICMAB−CSIC), Campus de Bellaterra, 08193 Bellaterra, Barcelona, Spain
| | - Stefano Ossicini
- “Centro S3”, CNR-Istituto di Nanoscienze, Via Campi 213/A, 41125 Modena, Italy
- Dipartimento di Scienze e Metodi dell’Ingegneria, Centro Interdipartimentale En&Tech, Università di Modena e Reggio Emilia, Via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia, Italy
| |
Collapse
|
26
|
Bernardi M, Palummo M, Grossman JC. Extraordinary sunlight absorption and one nanometer thick photovoltaics using two-dimensional monolayer materials. Nano Lett 2013; 13:3664-70. [PMID: 23750910 DOI: 10.1021/nl401544y] [Citation(s) in RCA: 668] [Impact Index Per Article: 60.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Graphene and monolayer transition metal dichalcogenides (TMDs) are promising materials for next-generation ultrathin optoelectronic devices. Although visually transparent, graphene is an excellent sunlight absorber, achieving 2.3% visible light absorbance in just 3.3 Å thickness. TMD monolayers also hold potential as sunlight absorbers, and may enable ultrathin photovoltaic (PV) devices due to their semiconducting character. In this work, we show that the three TMD monolayers MoS2, MoSe2, and WS2 can absorb up to 5-10% incident sunlight in a thickness of less than 1 nm, thus achieving 1 order of magnitude higher sunlight absorption than GaAs and Si. We further study PV devices based on just two stacked monolayers: (1) a Schottky barrier solar cell between MoS2 and graphene and (2) an excitonic solar cell based on a MoS2/WS2 bilayer. We demonstrate that such 1 nm thick active layers can attain power conversion efficiencies of up to ~1%, corresponding to approximately 1-3 orders of magnitude higher power densities than the best existing ultrathin solar cells. Our work shows that two-dimensional monolayer materials hold yet untapped potential for solar energy absorption and conversion at the nanoscale.
Collapse
Affiliation(s)
- Marco Bernardi
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States
| | | | | |
Collapse
|
27
|
Hogan C, Palummo M, Gierschner J, Rubio A. Correlation effects in the optical spectra of porphyrin oligomer chains: Exciton confinement and length dependence. J Chem Phys 2013; 138:024312. [DOI: 10.1063/1.4773582] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
28
|
Abstract
The recent advent of two-dimensional monolayer materials with tunable optical properties and high carrier mobility offers renewed opportunities for efficient, ultrathin excitonic solar cells alternative to those based on conjugated polymer and small molecule donors. Using first-principles density functional theory and many-body calculations, we demonstrate that monolayers of hexagonal BN and graphene (CBN) combined with commonly used acceptors such as PCBM fullerene or semiconducting carbon nanotubes can provide excitonic solar cells with tunable absorber gap, donor-acceptor interface band alignment, and power conversion efficiency, as well as novel device architectures. For the case of CBN-PCBM devices, we predict power conversion efficiency limits in the 10-20% range depending on the CBN monolayer structure. Our results demonstrate the possibility of using monolayer materials in tunable, efficient, ultrathin solar cells in which unexplored exciton and carrier transport regimes are at play.
Collapse
Affiliation(s)
- Marco Bernardi
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge Massachusetts 02139-4307, United States
| | | | | |
Collapse
|
29
|
Bernardi M, Palummo M, Grossman JC. Optoelectronic properties in monolayers of hybridized graphene and hexagonal boron nitride. Phys Rev Lett 2012; 108:226805. [PMID: 23003640 DOI: 10.1103/physrevlett.108.226805] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Indexed: 06/01/2023]
Abstract
We explain the nature of the electronic energy gap and optical absorption spectrum of carbon-boron-nitride (CBN) monolayers using density functional theory, GW and Bethe-Salpeter calculations. The band structure and the optical absorption are regulated by the C domain size rather than the composition (as customary for bulk semiconductor alloys). The C and BN quasiparticle states lie at separate energy for C and BN, with little mixing for energies near the band edge where states are chiefly C in character. The resulting optical absorption spectra show two distinct peaks whose energy and relative intensity vary with composition in agreement with the experiment. The monolayers present strongly bound excitons localized within the C domains, with binding energies of the order of 0.5-1.5 eV dependent on the C domain size. The optoelectronic properties result from the overall monolayer band structure, and cannot be understood as a superposition of the properties of bulklike C and BN domains.
Collapse
Affiliation(s)
- Marco Bernardi
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachuetts 02139-4307, USA
| | | | | |
Collapse
|
30
|
Bussetti G, Bonanni B, Cirilli S, Violante A, Russo M, Goletti C, Chiaradia P, Pulci O, Palummo M, Del Sole R, Gargiani P, Betti MG, Mariani C, Feenstra RM, Meyer G, Rieder KH. Coexistence of negatively and positively buckled isomers on n+-doped Si(111) − 2 × 1. Phys Rev Lett 2011; 106:067601. [PMID: 21405496 DOI: 10.1103/physrevlett.106.067601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Indexed: 05/30/2023]
Abstract
A long-standing puzzle regarding the Si(111) − 2 × 1 surface has been solved. The surface energy gap previously determined by photoemission on heavily n-doped crystals was not compatible with a strongly bound exciton known from other considerations to exist. New low-temperature angle-resolved photoemission and scanning tunneling microscopy data, together with theory, unambiguously reveal that isomers with opposite bucklings and different energy gaps coexist on such surfaces. The subtle energetics between the isomers, dependent on doping, leads to a reconciliation of all previous results.
Collapse
Affiliation(s)
- G Bussetti
- Dipartimento di Fisica, NAST and CNISM, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Ossicini S, Amato M, Guerra R, Palummo M, Pulci O. Silicon and Germanium Nanostructures for Photovoltaic Applications: Ab-Initio Results. Nanoscale Res Lett 2010; 5:1637-49. [PMID: 21076696 PMCID: PMC2956023 DOI: 10.1007/s11671-010-9688-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 07/01/2010] [Indexed: 05/25/2023]
Abstract
Actually, most of the electric energy is being produced by fossil fuels and great is the search for viable alternatives. The most appealing and promising technology is photovoltaics. It will become truly mainstream when its cost will be comparable to other energy sources. One way is to significantly enhance device efficiencies, for example by increasing the number of band gaps in multijunction solar cells or by favoring charge separation in the devices. This can be done by using cells based on nanostructured semiconductors. In this paper, we will present ab-initio results of the structural, electronic and optical properties of (1) silicon and germanium nanoparticles embedded in wide band gap materials and (2) mixed silicon-germanium nanowires. We show that theory can help in understanding the microscopic processes important for devices performances. In particular, we calculated for embedded Si and Ge nanoparticles the dependence of the absorption threshold on size and oxidation, the role of crystallinity and, in some cases, the recombination rates, and we demonstrated that in the case of mixed nanowires, those with a clear interface between Si and Ge show not only a reduced quantum confinement effect but display also a natural geometrical separation between electron and hole.
Collapse
Affiliation(s)
- Stefano Ossicini
- Dipartimento di Scienze e Metodi dell’Ingegneria, Universitá di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, 42122, Reggio Emilia, Italy
- Centro S3, CNR-Istituto di Nanoscienze, Via Campi 213A, I-41125, Modena, Italy
| | - Michele Amato
- Centro S3, CNR-Istituto di Nanoscienze, Via Campi 213A, I-41125, Modena, Italy
- Dipartimento di Fisica, Università di Modena e Reggio Emilia, via Campi 213/A, 41125, Modena, Italy
| | - Roberto Guerra
- Centro S3, CNR-Istituto di Nanoscienze, Via Campi 213A, I-41125, Modena, Italy
- Dipartimento di Fisica, Università di Modena e Reggio Emilia, via Campi 213/A, 41125, Modena, Italy
| | - Maurizia Palummo
- European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Dipartimento di Fisica, Università di Roma, ‘Tor Vergata’, via della Ricerca Scientifica 1, 00133, Roma, Italy
| | - Olivia Pulci
- European Theoretical Spectroscopy Facility (ETSF), NAST, Dipartimento di Fisica, Università di Roma, ‘Tor Vergata’, via della Ricerca Scientifica 1, 00133, Roma, Italy
| |
Collapse
|
32
|
Ruocco A, Chiodo L, Sforzini M, Palummo M, Monachesi P, Stefani G. Experimental and Theoretical Investigation of the Pyrrole/Al(100) Interface. J Phys Chem A 2009; 113:15193-7. [DOI: 10.1021/jp905537g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alessandro Ruocco
- Dipartimento di Fisica and CNISM Università Roma Tre, Roma, Italy, Nano-Bio Spectroscopy group and European Theoretical Spectroscopy Facility (ETSF), Dpto. de Física de Materiales, Universidad del País Vasco UPV/EHU and Centro Mixto CSIC-UPV/EHU, San Sebastían, Spain, Dipartimento di Fisica Università Roma Tre, Roma Italy, Dipartimento di Fisica, European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Università di Roma “Tor Vergata”, Roma, Italy, and Dipartimento di Fisica, Università de
| | - Letizia Chiodo
- Dipartimento di Fisica and CNISM Università Roma Tre, Roma, Italy, Nano-Bio Spectroscopy group and European Theoretical Spectroscopy Facility (ETSF), Dpto. de Física de Materiales, Universidad del País Vasco UPV/EHU and Centro Mixto CSIC-UPV/EHU, San Sebastían, Spain, Dipartimento di Fisica Università Roma Tre, Roma Italy, Dipartimento di Fisica, European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Università di Roma “Tor Vergata”, Roma, Italy, and Dipartimento di Fisica, Università de
| | - Massimo Sforzini
- Dipartimento di Fisica and CNISM Università Roma Tre, Roma, Italy, Nano-Bio Spectroscopy group and European Theoretical Spectroscopy Facility (ETSF), Dpto. de Física de Materiales, Universidad del País Vasco UPV/EHU and Centro Mixto CSIC-UPV/EHU, San Sebastían, Spain, Dipartimento di Fisica Università Roma Tre, Roma Italy, Dipartimento di Fisica, European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Università di Roma “Tor Vergata”, Roma, Italy, and Dipartimento di Fisica, Università de
| | - Maurizia Palummo
- Dipartimento di Fisica and CNISM Università Roma Tre, Roma, Italy, Nano-Bio Spectroscopy group and European Theoretical Spectroscopy Facility (ETSF), Dpto. de Física de Materiales, Universidad del País Vasco UPV/EHU and Centro Mixto CSIC-UPV/EHU, San Sebastían, Spain, Dipartimento di Fisica Università Roma Tre, Roma Italy, Dipartimento di Fisica, European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Università di Roma “Tor Vergata”, Roma, Italy, and Dipartimento di Fisica, Università de
| | - Patrizia Monachesi
- Dipartimento di Fisica and CNISM Università Roma Tre, Roma, Italy, Nano-Bio Spectroscopy group and European Theoretical Spectroscopy Facility (ETSF), Dpto. de Física de Materiales, Universidad del País Vasco UPV/EHU and Centro Mixto CSIC-UPV/EHU, San Sebastían, Spain, Dipartimento di Fisica Università Roma Tre, Roma Italy, Dipartimento di Fisica, European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Università di Roma “Tor Vergata”, Roma, Italy, and Dipartimento di Fisica, Università de
| | - Giovanni Stefani
- Dipartimento di Fisica and CNISM Università Roma Tre, Roma, Italy, Nano-Bio Spectroscopy group and European Theoretical Spectroscopy Facility (ETSF), Dpto. de Física de Materiales, Universidad del País Vasco UPV/EHU and Centro Mixto CSIC-UPV/EHU, San Sebastían, Spain, Dipartimento di Fisica Università Roma Tre, Roma Italy, Dipartimento di Fisica, European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Università di Roma “Tor Vergata”, Roma, Italy, and Dipartimento di Fisica, Università de
| |
Collapse
|
33
|
Palummo M, Hogan C, Sottile F, Bagalá P, Rubio A. Ab initio electronic and optical spectra of free-base porphyrins: The role of electronic correlation. J Chem Phys 2009; 131:084102. [DOI: 10.1063/1.3204938] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
34
|
Bruno M, Palummo M, Marini A, Del Sole R, Ossicini S. From Si nanowires to porous silicon: the role of excitonic effects. Phys Rev Lett 2007; 98:036807. [PMID: 17358714 DOI: 10.1103/physrevlett.98.036807] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Indexed: 05/14/2023]
Abstract
We show that the electronic and optical properties of silicon nanowires, with different size and orientation, are dominated by important many-body effects. The electronic and excitonic gaps, calculated within first principles, agree with the available experimental data. Huge excitonic effects, which depend strongly on wire orientation and size, characterize the optical spectra. Modeling porous silicon as a collection of interacting nanowires, we find an absorption spectrum which is in very good agreement with experimental measurements only when the electron-hole interaction is included.
Collapse
Affiliation(s)
- Mauro Bruno
- European Theoretical Spectroscopy Facility, CNR-INFM Institute for Statistical Mechanics and Complexity, CNISM and Dipartimento di Fisica, Universitá di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
| | | | | | | | | |
Collapse
|
35
|
Palummo M, Pulci O, Del Sole R, Marini A, Schwitters M, Haines SR, Williams KH, Martin DS, Weightman P, Butler JE. Reflectance anisotropy spectra of the diamond (100)-(2x1) surface: evidence of strongly bound surface state excitons. Phys Rev Lett 2005; 94:087404. [PMID: 15783931 DOI: 10.1103/physrevlett.94.087404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Indexed: 05/24/2023]
Abstract
We compare the results of ab initio calculations with measured reflection anisotropy spectra and show that strongly bound surface-state excitons occur on the clean diamond (100) surface. These excitons are found to have a binding energy close to 1 eV, the strongest ever observed at a semiconductor surface. Important electron-hole interaction effects on the line shape of the optical transitions above the surface-state gap are also found.
Collapse
Affiliation(s)
- Maurizia Palummo
- Dipartimento di Fisica-Universitá di Roma, Tor Vergata and Istituto Nazionale per la Fisica della Materia, I-00133 Rome, Italy
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Pulci O, Silvestrelli PL, Palummo M, Ancilotto F, Del Sole R. Ab-initio study of the adsorption of acetylene on Si(001) surface. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/pssc.200303850] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
37
|
|
38
|
Quiroga PA, Yuln GV, Palummo M, Cingolani A, Dall LL, Volonté MG. Comparative bioavailability of diltiazem in prolonged-release oral preparations. Drug Dev Ind Pharm 2001; 27:1099-106. [PMID: 11794812 DOI: 10.1081/ddc-100108372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
This study was conducted to compare the bioavailability of two prolonged-release pharmaceutical forms containing 300 mg of diltiazem. The test formulation is a new design of tablets with a hydrophilic matrix, and the reference formulation is capsules containing prolonged liberation microgranules, in the same dose, that are commercially available in the pharmaceutical market. Diltiazem plasma concentrations were analyzed by high-performance liquid chromatography (HPLC), which involves solid-phase extraction for plasma sample preparation. Twelve healthy volunteers participated in the study, which had a single-dose, two-treatment, two-sequence-crossover, randomized design. The preparations were compared using pharmacokinetic parameters such as the area under the plasma concentration-time curve AUC(0-36), peak plasma concentration Cmax, and Cmax/AUC(0-36) ratio as a measure for the absorption rate. No statistically significant difference was observed for any of the parameters, and the 90% confidence intervals calculated for the ratio of the logarithmically transformed AUC(0-36) and Cmax/AUC(0-36) values of both formulations were within the bioequivalence limit of 0.80-1.25. Moreover, an in vitro study of dissolution according to USP 23 was conducted, and the in vitro parameters were calculated.
Collapse
Affiliation(s)
- P A Quiroga
- Departamento Ciencias Biológicas, Facultad Ciencias Exactas, Universidad Nacional de La Plata, Argentina
| | | | | | | | | | | |
Collapse
|
39
|
|
40
|
Rohlfing M, Palummo M, Onida G. Structural and optical properties of the Ge(111)-(2 x 1) surface. Phys Rev Lett 2000; 85:5440-5443. [PMID: 11136016 DOI: 10.1103/physrevlett.85.5440] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2000] [Indexed: 05/23/2023]
Abstract
We study the two lowest-energy isomers of the Ge(111)-(2 x 1) surface, by a state-of-the-art first-principles calculation of their optical spectra, including the electron-hole interaction effects. A comparison of our results with the available experimental data suggests that, at difference with the silicon case, the stablest isomer differs from the standard "buckled Pandey chains" reconstruction. This conclusion is supported by accurate total-energy results.
Collapse
Affiliation(s)
- M Rohlfing
- Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Strasse 10, 48149 Münster, Germany
| | | | | |
Collapse
|
41
|
Palummo M, Cingolani A, Dall L, Volonté MG. Stability of capsules containing omeprazole in enteric coated pellets. Boll Chim Farm 2000; 139:124-8. [PMID: 10961022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
The aim of the present study was to comparatively evaluate the stability of capsules containing 20 mg of Omeprazole, in enteric coated pellets, from seven pharmaceutical laboratories on Argentine market. The stability test was performed under the conditions indicated by the ICH: 40 degrees C, 75% HR, with and without light, during a six month period. The remaining content of Omeprazole, total percentage of impurities and percentage of released active principle in vitro, were determined by HPLC. The organoleptic characteristics of the pellets were visually examined. The results obtained at six months indicate that, from the seven products studied, four were found to have a content of Omeprazole higher than 90% of the labeled amount, in both lighting conditions tested, and also comply with the USP23 specifications with respect to the release in vitro. We conclude that the progressive darkening of the pellets indicates, qualitatively, the level of degradation of the product and that the stability of Omeprazole depends on the correct formulation and the primary container.
Collapse
Affiliation(s)
- M Palummo
- Cátedra de Ensayo y Valoración de Medicamentos, Facultad de Ciencias Exactas, UNLP, La Plata, Argentina
| | | | | | | |
Collapse
|
42
|
|
43
|
|
44
|
Baldacchini G, Cremona M, Casalboni M, Grassano UM, Luci A, Palummo M, Casalis L, Minguzzi P, Pozzi F, Tonelli M, Scacco A. Optical properties of (F2+)H and F-aggregate centers in NaCl:OH- crystals. Phys Rev B Condens Matter 1991; 44:12189-12196. [PMID: 9999375 DOI: 10.1103/physrevb.44.12189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|