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Wang H, Wang X, Li D. Defects of monolayer PbI 2: a computational study. Phys Chem Chem Phys 2021; 23:20553-20559. [PMID: 34505581 DOI: 10.1039/d1cp01246k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PbI2 is highly desired for optoelectronics, particularly as a crucial precursor in the preparation of hybrid perovskites. Multifarious defects of PbI2 have been frequently observed in experiments; however, the origin and impact on its intrinsic properties are not clear currently. Hereby, a systematic study on the defects in PbI2 was performed by first principles calculations. Likely defect structures in both 1T and 1H phases were predicted, and the corresponding formation energies at the neutral and charged states based on the pre-estimated chemical potential of I/Pb were both calculated. At the neutral states, the formation energy of VI is relatively low, which is consistent with the experimental observation. However, at the charged states, VPb seems to be dominant regardless of the chemical potential and contributes more to the conductivity. Compared with the two-dimensional transition metal dichalcogenides, the relatively low formation energy of PbI2 indicates its flexibility and the weak Pb-I interaction. Our DFT calculations bring new insights into understanding the influence of defects on its opto-electrical performance and instruct to suppress the formation of those defects that are deleterious to its performance.
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Affiliation(s)
- Han Wang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
| | - Xiao Wang
- Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, P. R. China.
| | - Da Li
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
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Sharma G, Pandey VK, Datta S, Ghosh P. Effect of electron-phonon coupling on the transport properties of monolayers of ZrS 2, BiI 3 and PbI 2: a thermoelectric perspective. Phys Chem Chem Phys 2021; 23:11663-11671. [PMID: 33978013 DOI: 10.1039/d1cp00533b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thermoelectric materials are used for the conversion of waste heat to electrical energy. The transport coefficients that determine their thermoelectric properties depend on the band structure and the relaxation time of the charge carriers. Both of these are significantly affected by electron-phonon coupling. In this work, using a combination of density functional theory and semiclassical Boltzmann transport theory, we have studied the effect of electron-phonon coupling in monolayers of ZrS2, BiI3 and PbI2. Our results show that in these ionic materials charge carriers are primarily scattered by the optical modes that strongly couple with them. From our study it is conclusively shown that neglecting the contributions of optical modes to electron-phonon coupling in these low-dimensional ionic solids, as is usually done in the computation of relaxation time from deformation theory, results in severe overestimation of the relaxation time. In particular, neglecting the scattering of the optical phonons results in about two orders of magnitude overestimation of relaxation times in these materials. Moreover, we also find that the renormalization of the band structure not only results in the reduction of band gaps but also changes the band dispersion, which strongly affect different transport properties like the electrical conductivity and Seebeck coefficient. Amongst these three materials, we observe that carrier relaxation time due to electron-phonon scattering is reduced as the ionicity of the material decreases.
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Affiliation(s)
- Gautam Sharma
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India.
| | - Vineet Kumar Pandey
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India.
| | - Shouvik Datta
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India. and Centre for Energy Sciences, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - Prasenjit Ghosh
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India. and Centre for Energy Sciences, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
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Sinha S, Zhu T, France-Lanord A, Sheng Y, Grossman JC, Porfyrakis K, Warner JH. Atomic structure and defect dynamics of monolayer lead iodide nanodisks with epitaxial alignment on graphene. Nat Commun 2020; 11:823. [PMID: 32041958 PMCID: PMC7010709 DOI: 10.1038/s41467-020-14481-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 01/06/2020] [Indexed: 11/09/2022] Open
Abstract
Lead Iodide (PbI2) is a large bandgap 2D layered material that has potential for semiconductor applications. However, atomic level study of PbI2 monolayer has been limited due to challenges in obtaining thin crystals. Here, we use liquid exfoliation to produce monolayer PbI2 nanodisks (30-40 nm in diameter and > 99% monolayer purity) and deposit them onto suspended graphene supports to enable atomic structure study of PbI2. Strong epitaxial alignment of PbI2 monolayers with the underlying graphene lattice occurs, leading to a phase shift from the 1 T to 1 H structure to increase the level of commensuration in the two lattice spacings. The fundamental point vacancy and nanopore structures in PbI2 monolayers are directly imaged, showing rapid vacancy migration and self-healing. These results provide a detailed insight into the atomic structure of monolayer PbI2, and the impact of the strong van der Waals interaction with graphene, which has importance for future applications in optoelectronics.
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Affiliation(s)
- Sapna Sinha
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Taishan Zhu
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Arthur France-Lanord
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Yuewen Sheng
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Jeffrey C Grossman
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Kyriakos Porfyrakis
- Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Jamie H Warner
- Department of Mechanical Engineering, University of Texas at Austin, 204 Dean Keeton Street, Austin, 78712, USA.
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Achieving highly uniform two-dimensional PbI 2 flakes for photodetectors via space confined physical vapor deposition. Sci Bull (Beijing) 2017; 62:1654-1662. [PMID: 36659385 DOI: 10.1016/j.scib.2017.11.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 10/23/2017] [Accepted: 10/31/2017] [Indexed: 01/21/2023]
Abstract
Two-dimensional (2D) PbI2 flakes have been attracting intensive attention as one potential candidate for the modern optoelectronics. However, suffered from the instability of kinetics-driven growth, the fabricated 2D PbI2 flakes have a wide dimensional distribution even under the same conditions. Herein, a novel facile space confined physical vapor deposition (PVD) process is provided to synthesize uniform triangle PbI2 flakes with high quality. The confined space provides a relatively stable growth environment that renders more control on the growth kinetics, leading to highly uniform triangle PbI2 flakes with the average size of 5 µm and thickness of 17 nm. Moreover, as-fabricated PbI2-based photodetectors show promising stable and flexible optoelectronic performances to 470 nm light, including high responsivity (0.72 A W-1), large on/off ratio up to 900, fast photoresponse speed (rise time of 13.5 ms and decay time of 20 ms) and high detectivity (1.04 × 1010 Jones). The well-controllable growth of the uniform triangle PbI2 flakes and the detailed exploration of their optoelectronic properties are particularly valuable for their further practical applications.
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Iyikanat F, Kandemir A, Ozaydin HD, Senger RT, Sahin H. Hydrogenation-driven phase transition in single-layer TiSe 2. NANOTECHNOLOGY 2017; 28:495709. [PMID: 29048331 DOI: 10.1088/1361-6528/aa94ab] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
First-principles calculations based on density-functional theory are used to investigate the effects of hydrogenation on the structural, vibrational, thermal and electronic properties of the charge density wave (CDW) phase of single-layer TiSe2. It is found that hydrogenation of single-layer TiSe2 is possible through adsorption of a H atom on each Se site. Our total energy and phonon calculations reveal that a structural phase transition occurs from the CDW phase to the T d phase upon full hydrogenation. Fully hydrogenated TiSe2 presents a direct gap semiconducting behavior with a band gap of 119 meV. Full hydrogenation also leads to a significant decrease in the heat capacity of single-layer TiSe2.
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Affiliation(s)
- F Iyikanat
- Department of Physics, Izmir Institute of Technology, 35430, Izmir, Turkey
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Frisenda R, Island JO, Lado JL, Giovanelli E, Gant P, Nagler P, Bange S, Lupton JM, Schüller C, Molina-Mendoza AJ, Aballe L, Foerster M, Korn T, Angel Niño M, de Lara DP, Pérez EM, Fernandéz-Rossier J, Castellanos-Gomez A. Characterization of highly crystalline lead iodide nanosheets prepared by room-temperature solution processing. NANOTECHNOLOGY 2017; 28:455703. [PMID: 29039361 DOI: 10.1088/1361-6528/aa8e5c] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Two-dimensional (2D) semiconducting materials are particularly appealing for many applications. Although theory predicts a large number of 2D materials, experimentally only a few of these materials have been identified and characterized comprehensively in the ultrathin limit. Lead iodide, which belongs to the transition metal halides family and has a direct bandgap in the visible spectrum, has been known for a long time and has been well characterized in its bulk form. Nevertheless, studies of this material in the nanometer thickness regime are rather scarce. In this article we demonstrate an easy way to synthesize ultrathin, highly crystalline flakes of PbI2 by precipitation from a solution in water. We thoroughly characterize the produced thin flakes with different techniques ranging from optical and Raman spectroscopy to temperature-dependent photoluminescence and electron microscopy. We compare the results to ab initio calculations of the band structure of the material. Finally, we fabricate photodetectors based on PbI2 and study their optoelectronic properties.
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Affiliation(s)
- Riccardo Frisenda
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Campus de Cantoblanco, E-28049 Madrid, Spain
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