51
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Nan G, Beljonne D, Zhang X, Quarti C. Organic Cations Protect Methylammonium Lead Iodide Perovskites against Small Exciton-Polaron Formation. J Phys Chem Lett 2020; 11:2983-2991. [PMID: 32227856 DOI: 10.1021/acs.jpclett.0c00673] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Working organic-inorganic lead halide perovskite-based devices are notoriously sensitive to surface and interface effects. Using a combination of density functional theory (DFT) and time-dependent DFT methods, we report a comprehensive study of the changes (with respect to the bulk) in geometric and electronic structures going on at the (001) surface of a (tetragonal phase) methylammonium lead iodide perovskite slab, in the dark and upon photoexcitation. The formation of a hydrogen bonding pattern between the -NH3 groups of the organic cations and the iodine atoms of the outer inorganic layout is found to critically contribute to the relative thermodynamic stability of slabs with varying surface compositions and terminations. Most importantly, our results show that the hydrogen bond locking effects induced by the MA groups tend to protect the external two-dimensional lattice against large local structural deformations, i.e., the formation of a small exciton-polaron, at variance with purely inorganic lead halide perovskites.
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Affiliation(s)
- Guangjun Nan
- Department of Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - Xu Zhang
- Department of Physics and Astronomy, California State University Northridge, Northridge, California 91330-8268, United States
| | - Claudio Quarti
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
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52
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Munson KT, Swartzfager JR, Gan J, Asbury JB. Does Dipolar Motion of Organic Cations Affect Polaron Dynamics and Bimolecular Recombination in Halide Perovskites? J Phys Chem Lett 2020; 11:3166-3172. [PMID: 32243757 DOI: 10.1021/acs.jpclett.0c00762] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The role of dipolar motion of organic cations in the A-sites of halide perovskites has been debated in an effort to understand why these materials possess such remarkable properties. Here, we show that the dipolar motion of cations such as methylammonium (MA) or formamidinium (FA) versus cesium (Cs) does not influence large polaron binding energies, delocalization lengths, formation times, or bimolecular recombination lifetimes in lead bromide perovskites containing only one type of A-site cation. We directly probe the transient absorption spectra of large polarons throughout the entire mid-infrared and resolve their dynamics on time scales from sub-100 fs to sub-μs using time-resolved mid-infrared spectroscopy. Our findings suggest that the improved optoelectronic properties reported of halide perovskites with mixed A-site cations may result from synergy among the cations and how their mixture modulates the structure and dynamics of the inorganic lattice rather than from the dipolar properties of the cations themselves.
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Affiliation(s)
- Kyle T Munson
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - John R Swartzfager
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jianing Gan
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - John B Asbury
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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53
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Hopper TR, Gorodetsky A, Jeong A, Krieg F, Bodnarchuk MI, Maimaris M, Chaplain M, Macdonald TJ, Huang X, Lovrincic R, Kovalenko MV, Bakulin AA. Hot Carrier Dynamics in Perovskite Nanocrystal Solids: Role of the Cold Carriers, Nanoconfinement, and the Surface. NANO LETTERS 2020; 20:2271-2278. [PMID: 32142303 DOI: 10.1021/acs.nanolett.9b04491] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Carrier cooling is of widespread interest in the field of semiconductor science. It is linked to carrier-carrier and carrier-phonon coupling and has profound implications for the photovoltaic performance of materials. Recent transient optical studies have shown that a high carrier density in lead-halide perovskites (LHPs) can reduce the cooling rate through a "phonon bottleneck". However, the role of carrier-carrier interactions, and the material properties that control cooling in LHPs, is still disputed. To address these factors, we utilize ultrafast "pump-push-probe" spectroscopy on LHP nanocrystal (NC) films. We find that the addition of cold carriers to LHP NCs increases the cooling rate, competing with the phonon bottleneck. By comparing different NCs and bulk samples, we deduce that the cooling behavior is intrinsic to the LHP composition and independent of the NC size or surface. This can be contrasted with other colloidal nanomaterials, where confinement and trapping considerably influence the cooling dynamics.
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Affiliation(s)
- Thomas R Hopper
- Department of Chemistry, Imperial College London, London W12 0BZ, United Kingdom
| | - Andrei Gorodetsky
- Department of Chemistry, Imperial College London, London W12 0BZ, United Kingdom
| | - Ahhyun Jeong
- Department of Chemistry, Imperial College London, London W12 0BZ, United Kingdom
| | - Franziska Krieg
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
- Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
| | - Maryna I Bodnarchuk
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
- Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
| | - Marios Maimaris
- Department of Chemistry, Imperial College London, London W12 0BZ, United Kingdom
| | - Marine Chaplain
- Department of Chemistry, Imperial College London, London W12 0BZ, United Kingdom
| | - Thomas J Macdonald
- Department of Chemistry, Imperial College London, London W12 0BZ, United Kingdom
| | - Xiaokun Huang
- Institute for High-Frequency Technology, Technische Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
- InnovationLab, Speyerer Strasse 4, 69115 Heidelberg, Germany
- Kirchhoff Institute for Physics, University of Heidelberg, 69120 Heidelberg, Germany
| | - Robert Lovrincic
- Institute for High-Frequency Technology, Technische Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
- InnovationLab, Speyerer Strasse 4, 69115 Heidelberg, Germany
| | - Maksym V Kovalenko
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
- Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
| | - Artem A Bakulin
- Department of Chemistry, Imperial College London, London W12 0BZ, United Kingdom
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54
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Boehme SC, Brinck ST, Maes J, Yazdani N, Zapata F, Chen K, Wood V, Hodgkiss JM, Hens Z, Geiregat P, Infante I. Phonon-Mediated and Weakly Size-Dependent Electron and Hole Cooling in CsPbBr 3 Nanocrystals Revealed by Atomistic Simulations and Ultrafast Spectroscopy. NANO LETTERS 2020; 20:1819-1829. [PMID: 32049539 PMCID: PMC7997624 DOI: 10.1021/acs.nanolett.9b05051] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 02/11/2020] [Indexed: 05/25/2023]
Abstract
We combine state-of-the-art ultrafast photoluminescence and absorption spectroscopy and nonadiabatic molecular dynamics simulations to investigate charge-carrier cooling in CsPbBr3 nanocrystals over a very broad size regime, from 0.8 to 12 nm. Contrary to the prevailing notion that polaron formation slows down charge-carrier cooling in lead-halide perovskites, no suppression of carrier cooling is observed in CsPbBr3 nanocrystals except for a slow cooling (over ∼10 ps) of "warm" electrons in the vicinity (within ∼0.1 eV) of the conduction band edge. At higher excess energies, electrons and holes cool with similar rates, on the order of 1 eV ps-1 carrier-1, increasing weakly with size. Our ab initio simulations suggest that cooling proceeds via fast phonon-mediated intraband transitions driven by strong and size-dependent electron-phonon coupling. The presented experimental and computational methods yield the spectrum of involved phonons and may guide the development of devices utilizing hot charge carriers.
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Affiliation(s)
- Simon C. Boehme
- Department
of Theoretical Chemistry, Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Stephanie ten Brinck
- Department
of Theoretical Chemistry, Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Jorick Maes
- Department
of Chemistry, Faculty of Sciences, Universiteit
Gent, Krijgslaan 281, 9000 Gent, Belgium
| | - Nuri Yazdani
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, GH 8092 Zurich, Switzerland
| | - Felipe Zapata
- Netherlands
eScience Center, Science Park 140 (Matrix I), 1098 XG Amsterdam, The Netherlands
| | - Kai Chen
- The
MacDiarmid Institute for Advanced Materials and Nanotechnology, School
of Chemical and Physical Sciences, Victoria
University of Wellington, 6012 Wellington, New Zealand
| | - Vanessa Wood
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, GH 8092 Zurich, Switzerland
| | - Justin M. Hodgkiss
- The
MacDiarmid Institute for Advanced Materials and Nanotechnology, School
of Chemical and Physical Sciences, Victoria
University of Wellington, 6012 Wellington, New Zealand
| | - Zeger Hens
- Department
of Chemistry, Faculty of Sciences, Universiteit
Gent, Krijgslaan 281, 9000 Gent, Belgium
| | - Pieter Geiregat
- Department
of Chemistry, Faculty of Sciences, Universiteit
Gent, Krijgslaan 281, 9000 Gent, Belgium
| | - Ivan Infante
- Department
of Theoretical Chemistry, Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
- Department
of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
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55
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Dong H, Zhang C, Liu X, Yao J, Zhao YS. Materials chemistry and engineering in metal halide perovskite lasers. Chem Soc Rev 2020; 49:951-982. [PMID: 31960011 DOI: 10.1039/c9cs00598f] [Citation(s) in RCA: 127] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The invention and development of the laser have revolutionized science, technology, and industry. Metal halide perovskites are an emerging class of semiconductors holding promising potential in further advancing the laser technology. In this Review, we provide a comprehensive overview of metal halide perovskite lasers from the viewpoint of materials chemistry and engineering. After an introduction to the materials chemistry and physics of metal halide perovskites, we present diverse optical cavities for perovskite lasers. We then comprehensively discuss various perovskite lasers with particular functionalities, including tunable lasers, multicolor lasers, continuous-wave lasers, single-mode lasers, subwavelength lasers, random lasers, polariton lasers, and laser arrays. Following this a description of the strategies for improving the stability and reducing the toxicity of metal halide perovskite lasers is provided. Finally, future research directions and challenges toward practical technology applications of perovskite lasers are provided to give an outlook on this emerging field.
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Affiliation(s)
- Haiyun Dong
- Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
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56
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Lan Y, Tao X, Kong X, He Y, Zheng X, Sutton M, Kanatzidis MG, Guo H, Cooke DG. Coherent charge-phonon correlations and exciton dynamics in orthorhombic CH3NH3PbI3 measured by ultrafast multi-THz spectroscopy. J Chem Phys 2019; 151:214201. [DOI: 10.1063/1.5127992] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Yang Lan
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Xixi Tao
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Xianghua Kong
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Yihui He
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Xiaohong Zheng
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Mark Sutton
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | | | - Hong Guo
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - David G. Cooke
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
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57
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Joshi PP, Maehrlein SF, Zhu X. Dynamic Screening and Slow Cooling of Hot Carriers in Lead Halide Perovskites. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1803054. [PMID: 30672044 DOI: 10.1002/adma.201803054] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Revised: 10/03/2018] [Indexed: 06/09/2023]
Abstract
Among the exceptional properties of lead halide perovskites (LHPs) is the ultraslow cooling of hot carriers. Carrier densities below the Mott density for large polarons (≤ ≈1018 cm-3 ) are focused on here. As in other semiconductors, a nascent hot electron distribution initially cools down via emission of longitudinal optical (LO) phonons on the 10-14 -10-13 s timescale. What distinguishes LHPs from conventional semiconductors is the exceptionally efficient screening in the former. The dielectric screening in LHPs on the 10-13 s timescale results in an order-of-magnitude reduction in the Coulomb potential upon the formation of a large polaron, likely with ferroelectric-like local ordering. Further LO-phonon emission is inhibited, and this leads to partial retention of hot electron energy on the 10-12 s timescale, more so in hybrid LHPs than in their all-inorganic counterparts. Further cooling of hot polarons occurs on the 10-10 s timescale, and this can be attributed to the slow diffusion of heat out of the large polaron volume due to the low thermal conductivity of LHPs. Like other carrier properties, slow hot carrier cooling in LHPs can be intimately related to efficient screening in a soft, anharmonic, and dynamically disordered lattice.
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Affiliation(s)
| | | | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
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58
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Kaur G, Justice Babu K, Ghorai N, Goswami T, Maiti S, Ghosh HN. Polaron-Mediated Slow Carrier Cooling in a Type-1 3D/0D CsPbBr 3@Cs 4PbBr 6 Core-Shell Perovskite System. J Phys Chem Lett 2019; 10:5302-5311. [PMID: 31442050 DOI: 10.1021/acs.jpclett.9b01552] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Rapid hot carrier cooling is the key loss channel overriding all possible energy loss pathways that limit achievable solar conversion efficiency. Thus, delayed hot carrier cooling in the cell absorber layer can make hot carrier extraction a less cumbersome task, assisting in the realization of hot carrier solar cells. There have been plentitude of reports concerning the slow carrier cooling in perovskite materials, which eventually triggered interest in radical understanding of the native photophysics driving the device design. Here in this finding, a further dramatic dip in the cooling rate has been discerned upon a growing Cs4PbBr6 shell over CsPbBr3 core nanocrystals (NCs), in contrast to the bare CsPbBr3 core NCs. Using transient absorption spectroscopy, we investigated the disparity in the hot carrier thermalization pathways in the CsPbBr3 and CsPbBr3@Cs4PbBr6 core-shell NCs under the same laser fluence, which can be validated as a corollary of polaron formation in the later NCs.
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Affiliation(s)
- Gurpreet Kaur
- Institute of Nano Science and Technology , Mohali , Punjab 160062 , India
| | - K Justice Babu
- Institute of Nano Science and Technology , Mohali , Punjab 160062 , India
| | - Nandan Ghorai
- Institute of Nano Science and Technology , Mohali , Punjab 160062 , India
| | - Tanmay Goswami
- Institute of Nano Science and Technology , Mohali , Punjab 160062 , India
| | - Sourav Maiti
- Institute of Nano Science and Technology , Mohali , Punjab 160062 , India
- Radiation and Photochemistry Division , Bhabha Atomic Research Centre , Mumbai 400085 , India
| | - Hirendra N Ghosh
- Institute of Nano Science and Technology , Mohali , Punjab 160062 , India
- Radiation and Photochemistry Division , Bhabha Atomic Research Centre , Mumbai 400085 , India
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59
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Nguyen XT, Timmer D, Rakita Y, Cahen D, Steinhoff A, Jahnke F, Lienau C, De Sio A. Ultrafast Charge Carrier Relaxation in Inorganic Halide Perovskite Single Crystals Probed by Two-Dimensional Electronic Spectroscopy. J Phys Chem Lett 2019; 10:5414-5421. [PMID: 31449755 DOI: 10.1021/acs.jpclett.9b01936] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Halide perovskites are promising optoelectronic materials. Despite impressive device performance, especially in photovoltaics, the femtosecond dynamics of elementary optical excitations and their interactions are still debated. Here we combine ultrafast two-dimensional electronic spectroscopy (2DES) and semiconductor Bloch equations (SBEs) to probe the room-temperature dynamics of nonequilibrium excitations in CsPbBr3 crystals. Experimentally, we distinguish between excitonic and free-carrier transitions, extracting a ∼30 meV exciton binding energy, in agreement with our SBE calculations and with recent experimental studies. The 2DES dynamics indicate remarkably short, <30 fs carrier relaxation at a ∼3 meV/fs rate, much faster than previously anticipated for this material, but similar to that in direct band gap semiconductors such as GaAs. Dynamic screening of excitons by free carriers also develops on a similarly fast <30 fs time scale, emphasizing the role of carrier-carrier interactions for this material's optical properties. Our results suggest that strong electron-phonon couplings lead to ultrafast relaxation of charge carriers, which, in turn may limit halide perovskites' carrier mobilities.
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Affiliation(s)
- Xuan Trung Nguyen
- Institut für Physik , Carl von Ossietzky Universität , 26129 Oldenburg , Germany
| | - Daniel Timmer
- Institut für Physik , Carl von Ossietzky Universität , 26129 Oldenburg , Germany
| | - Yevgeny Rakita
- Department of Materials & Interfaces , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - David Cahen
- Department of Materials & Interfaces , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - Alexander Steinhoff
- Institut für Theoretische Physik , Universität Bremen , 28359 Bremen , Germany
| | - Frank Jahnke
- Institut für Theoretische Physik , Universität Bremen , 28359 Bremen , Germany
| | - Christoph Lienau
- Institut für Physik , Carl von Ossietzky Universität , 26129 Oldenburg , Germany
| | - Antonietta De Sio
- Institut für Physik , Carl von Ossietzky Universität , 26129 Oldenburg , Germany
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60
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Mondal N, De A, Das S, Paul S, Samanta A. Ultrafast carrier dynamics of metal halide perovskite nanocrystals and perovskite-composites. NANOSCALE 2019; 11:9796-9818. [PMID: 31070653 DOI: 10.1039/c9nr01745c] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Perovskite nanocrystals (NCs), especially those based on cesium lead halides, have emerged in recent years as highly promising materials for efficient solar cells and photonic applications. The key to realization of full potential of these materials lies however in the molecular level understanding of the processes triggered by light. Herein we highlight the knowledge gained from photophysical investigations on these NCs of various sizes and compositions employing primarily the femtosecond pump-probe technique. We show how spectral and temporal characterization of the photo-induced transients provide insight into the mechanism and dynamics of relaxation of hot and thermalized charge carriers through their recombination and trapping. We discuss how the multiple excitons including the charged ones (trions), generated using high pump fluence or photon energy, recombine through the Auger-assisted process. We discussed the harvesting of hot carriers prior to their cooling and band-edge carriers from these perovskite NCs to wide band-gap metal oxides, metal chalcogenide NCs and molecular acceptors. How perovskites can influence the charge carrier dynamics in composites of organic and inorganic semiconductors is also discussed.
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Affiliation(s)
- Navendu Mondal
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India. E-mail:
| | - Apurba De
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India. E-mail:
| | - Somnath Das
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India. E-mail:
| | - Sumanta Paul
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India. E-mail:
| | - Anunay Samanta
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India. E-mail:
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61
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Li Y, Lai R, Luo X, Liu X, Ding T, Lu X, Wu K. On the absence of a phonon bottleneck in strongly confined CsPbBr 3 perovskite nanocrystals. Chem Sci 2019; 10:5983-5989. [PMID: 31360405 PMCID: PMC6566378 DOI: 10.1039/c9sc01339c] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 05/05/2019] [Indexed: 01/22/2023] Open
Abstract
In traditional solar cells, photogenerated energetic carriers (so-called hot carriers) rapidly relax to band edges via emission of phonons, prohibiting the extraction of their excess energy above the band gap. Quantum confined semiconductor nanocrystals, or quantum dots (QDs), were predicted to have long-lived hot carriers enabled by a phonon bottleneck, i.e., the large inter-level spacings in QDs should result in inefficient phonon emissions. Here we study the effect of quantum confinement on hot carrier/exciton lifetime in lead halide perovskite nanocrystals. We synthesized a series of strongly confined CsPbBr3 nanocrystals with edge lengths down to 2.6 nm, the smallest reported to date, and studied their hot exciton relaxation using ultrafast spectroscopy. We observed sub-ps hot exciton lifetimes in all the samples with edge lengths within 2.6-6.2 nm and thus the absence of a phonon bottleneck. Their well-resolved excitonic peaks allowed us to quantify hot carrier/exciton energy loss rates which increased with decreasing NC sizes. This behavior can be well reproduced by a nonadiabatic transition mechanism between excitonic states induced by coupling to surface ligands.
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Affiliation(s)
- Yulu Li
- State Key Laboratory of Molecular Reaction Dynamics , Dynamics Research Center for Energy and Environmental Materials , Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian , 116023 , China . .,Departmental of Chemistry , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen , Fujian 361005 , China
| | - Runchen Lai
- State Key Laboratory of Molecular Reaction Dynamics , Dynamics Research Center for Energy and Environmental Materials , Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian , 116023 , China .
| | - Xiao Luo
- State Key Laboratory of Molecular Reaction Dynamics , Dynamics Research Center for Energy and Environmental Materials , Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian , 116023 , China .
| | - Xue Liu
- State Key Laboratory of Molecular Reaction Dynamics , Dynamics Research Center for Energy and Environmental Materials , Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian , 116023 , China .
| | - Tao Ding
- State Key Laboratory of Molecular Reaction Dynamics , Dynamics Research Center for Energy and Environmental Materials , Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian , 116023 , China .
| | - Xin Lu
- Departmental of Chemistry , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen , Fujian 361005 , China
| | - Kaifeng Wu
- State Key Laboratory of Molecular Reaction Dynamics , Dynamics Research Center for Energy and Environmental Materials , Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian , 116023 , China .
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62
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Lan Y, Dringoli BJ, Valverde-Chávez DA, Ponseca CS, Sutton M, He Y, Kanatzidis MG, Cooke DG. Ultrafast correlated charge and lattice motion in a hybrid metal halide perovskite. SCIENCE ADVANCES 2019; 5:eaaw5558. [PMID: 31172030 PMCID: PMC6544455 DOI: 10.1126/sciadv.aaw5558] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 04/17/2019] [Indexed: 05/26/2023]
Abstract
Hybrid organic-inorganic halide perovskites have shown remarkable optoelectronic properties, exhibiting an impressive tolerance to defects believed to originate from correlated motion of charge carriers and the polar lattice forming large polarons. Few experimental techniques are capable of directly probing these correlations, requiring simultaneous sub-millielectron volt energy and femtosecond temporal resolution after absorption of a photon. Here, we use time-resolved multi-THz spectroscopy, sensitive to the internal excitations of the polaron, to temporally and energetically resolve the coherent coupling of charges to longitudinal optical phonons in single-crystal CH3NH3PbI3 (MAPI). We observe room temperature intraband quantum beats arising from the coherent displacement of charge from the coupled phonon cloud. Our measurements provide strong evidence for the existence of polarons in MAPI at room temperature, suggesting that electron/hole-phonon coupling is a defining aspect of the hybrid metal-halide perovskites contributing to the protection from scattering and enhanced carrier lifetimes that define their usefulness in devices.
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Affiliation(s)
- Yang Lan
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
| | | | | | - Carlito S. Ponseca
- Division of Biomolecular and Organic Electronics, IFM, Linköpings Universitet, Linköping SE- 58183, Sweden
| | - Mark Sutton
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
| | - Yihui He
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | | | - David G. Cooke
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
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63
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Cinquanta E, Meggiolaro D, Motti SG, Gandini M, Alcocer MJP, Akkerman QA, Vozzi C, Manna L, De Angelis F, Petrozza A, Stagira S. Ultrafast THz Probe of Photoinduced Polarons in Lead-Halide Perovskites. PHYSICAL REVIEW LETTERS 2019; 122:166601. [PMID: 31075027 DOI: 10.1103/physrevlett.122.166601] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 03/01/2019] [Indexed: 06/09/2023]
Abstract
We study the nature of photoexcited charge carriers in CsPbBr_{3} nanocrystal thin films by ultrafast optical pump-THz probe spectroscopy. We observe a deviation from a pure Drude dispersion of the THz dielectric response that is ascribed to the polaronic nature of carriers; a transient blueshift of observed phonon frequencies is indicative of the coupling between photogenerated charges and stretching-bending modes of the deformed inorganic sublattice, as confirmed by DFT calculations.
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Affiliation(s)
- Eugenio Cinquanta
- Dipartimento di Fisica, Politecnico di Milano, 20133, Milano, Italy
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, 20133, Milano, Italy
| | - Daniele Meggiolaro
- Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Istituto CNR di Scienze e Tecnologie Molecolari (ISTM-CNR), Via Elce di Sotto 8, 06123, Perugia, Italy
- CompuNet, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Silvia G Motti
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, 20133, Milano, Italy
| | - Marina Gandini
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, 20133, Milano, Italy
| | - Marcelo J P Alcocer
- Dipartimento di Fisica, Politecnico di Milano, 20133, Milano, Italy
- Solid State Physics and NanoLund, Lund University, P.O. Box 118, SE-221 00, Lund, Sweden
| | - Quinten A Akkerman
- Department of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy
- Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, Via Dodecaneso, 31, 16146, Genova, Italy
| | - Caterina Vozzi
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, 20133, Milano, Italy
| | - Liberato Manna
- Department of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy
| | - Filippo De Angelis
- Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Istituto CNR di Scienze e Tecnologie Molecolari (ISTM-CNR), Via Elce di Sotto 8, 06123, Perugia, Italy
- CompuNet, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Via Elce di Sotto 8, I-06123, Perugia, Italy
| | - Annamaria Petrozza
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, 20133, Milano, Italy
| | - Salvatore Stagira
- Dipartimento di Fisica, Politecnico di Milano, 20133, Milano, Italy
- Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, 20133, Milano, Italy
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64
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Suppressed phase separation of mixed-halide perovskites confined in endotaxial matrices. Nat Commun 2019; 10:695. [PMID: 30741944 PMCID: PMC6370784 DOI: 10.1038/s41467-019-08610-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 01/14/2019] [Indexed: 12/24/2022] Open
Abstract
The functionality and performance of a semiconductor is determined by its bandgap. Alloying, as for instance in InxGa1-xN, has been a mainstream strategy for tuning the bandgap. Keeping the semiconductor alloys in the miscibility gap (being homogeneous), however, is non-trivial. This challenge is now being extended to halide perovskites – an emerging class of photovoltaic materials. While the bandgap can be conveniently tuned by mixing different halogen ions, as in CsPb(BrxI1-x)3, the so-called mixed-halide perovskites suffer from severe phase separation under illumination. Here, we discover that such phase separation can be highly suppressed by embedding nanocrystals of mixed-halide perovskites in an endotaxial matrix. The tuned bandgap remains remarkably stable under extremely intensive illumination. The agreement between the experiments and a nucleation model suggests that the size of the nanocrystals and the host-guest interfaces are critical for the photo-stability. The stabilized bandgap will be essential for the development of perovskite-based optoelectronics, such as tandem solar cells and full-color LEDs. The bandgap of mixed-halide perovskites can be continuously tuned by changing the halide ratio, but the crystals have poor photo-stability. Here the authors show that photoinduced phase separation is suppressed when perovskite nanocrystals are embedded in a non-perovskite endotaxial matrix.
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65
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Chen J, Messing ME, Zheng K, Pullerits T. Cation-Dependent Hot Carrier Cooling in Halide Perovskite Nanocrystals. J Am Chem Soc 2019; 141:3532-3540. [DOI: 10.1021/jacs.8b11867] [Citation(s) in RCA: 130] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Junsheng Chen
- Chemical Physics and NanoLund, Lund University, Box 124, 22100 Lund, Sweden
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Maria E. Messing
- Solid State Physics and NanoLund, Lund University, Box 118, 22100 Lund, Sweden
| | - Kaibo Zheng
- Chemical Physics and NanoLund, Lund University, Box 124, 22100 Lund, Sweden
- Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Tonu Pullerits
- Chemical Physics and NanoLund, Lund University, Box 124, 22100 Lund, Sweden
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66
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Yan B, Wan D, Chi X, Li C, Motapothula MR, Hooda S, Yang P, Huang Z, Zeng S, Ramesh AG, Pennycook SJ, Rusydi A, Martin J, Venkatesan T. Anatase TiO 2-A Model System for Large Polaron Transport. ACS APPLIED MATERIALS & INTERFACES 2018; 10:38201-38208. [PMID: 30362340 DOI: 10.1021/acsami.8b11643] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Large polarons have been of significant recent technological interest as they screen and protect electrons from point-scattering centers. Anatase TiO2 is a model system for studying large polarons as they can be studied systematically over a wide range of temperature and carrier density. The electronic and magneto transport properties of reduced anatase TiO2 epitaxial thin films are analyzed considering various polaronic effects. Unexpectedly, with increasing carrier concentration, the mobility increases, which rarely happens in common metallic systems. We find that the screening of the electron-phonon (e-ph) coupling by excess carriers is necessary to explain this unusual dependence. We also find that the magnetoresistance could be decomposed into a linear and a quadratic component, separately characterizing the carrier transport and trapping as a function of temperature, respectively. The various transport behaviors could be organized into a single phase diagram, which clarifies the evolution of large polaron in this material.
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Affiliation(s)
- Bixing Yan
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
| | - Dongyang Wan
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
| | - Xiao Chi
- Singapore Synchrotron Light Source , National University of Singapore , Singapore 117603 , Singapore
| | - Changjian Li
- Department of Material Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | | | - Sonu Hooda
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
| | - Ping Yang
- Singapore Synchrotron Light Source , National University of Singapore , Singapore 117603 , Singapore
| | - Zhen Huang
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
| | - Shengwei Zeng
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
| | - Akash Gadekar Ramesh
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
| | - Stephen John Pennycook
- Department of Material Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Andrivo Rusydi
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
- Singapore Synchrotron Light Source , National University of Singapore , Singapore 117603 , Singapore
| | | | - Thirumalai Venkatesan
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
- Department of Material Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
- NUS Graduate School for Integrative Sciences and Engineering , National University of Singapore , Singapore 117456 , Singapore
- Department of Electrical and Computer Engineering , National University of Singapore , Singapore 117583 , Singapore
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67
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Grechko M, Bretschneider SA, Vietze L, Kim H, Bonn M. Kopplung von hoch- und niederfrequenten Schwingungsmoden in organisch-anorganischen Perowskiten. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201806676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Maksim Grechko
- Abteilung für molekulare Spektroskopie; Max-Planck-Institut für Polymerforschung; Ackermannweg 10 55128 Mainz Deutschland
| | - Simon A. Bretschneider
- Abteilung für molekulare Spektroskopie; Max-Planck-Institut für Polymerforschung; Ackermannweg 10 55128 Mainz Deutschland
| | - Laura Vietze
- Abteilung für molekulare Spektroskopie; Max-Planck-Institut für Polymerforschung; Ackermannweg 10 55128 Mainz Deutschland
| | - Heejae Kim
- Abteilung für molekulare Spektroskopie; Max-Planck-Institut für Polymerforschung; Ackermannweg 10 55128 Mainz Deutschland
| | - Mischa Bonn
- Abteilung für molekulare Spektroskopie; Max-Planck-Institut für Polymerforschung; Ackermannweg 10 55128 Mainz Deutschland
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68
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Grechko M, Bretschneider SA, Vietze L, Kim H, Bonn M. Vibrational Coupling between Organic and Inorganic Sublattices of Hybrid Perovskites. Angew Chem Int Ed Engl 2018; 57:13657-13661. [DOI: 10.1002/anie.201806676] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Maksim Grechko
- Department of Molecular Spectroscopy; Max Planck Institute for Polymer Research; Ackermannweg 10 55128 Mainz Germany
| | - Simon A. Bretschneider
- Department of Molecular Spectroscopy; Max Planck Institute for Polymer Research; Ackermannweg 10 55128 Mainz Germany
| | - Laura Vietze
- Department of Molecular Spectroscopy; Max Planck Institute for Polymer Research; Ackermannweg 10 55128 Mainz Germany
| | - Heejae Kim
- Department of Molecular Spectroscopy; Max Planck Institute for Polymer Research; Ackermannweg 10 55128 Mainz Germany
| | - Mischa Bonn
- Department of Molecular Spectroscopy; Max Planck Institute for Polymer Research; Ackermannweg 10 55128 Mainz Germany
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69
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Hopper T, Gorodetsky A, Frost JM, Müller C, Lovrincic R, Bakulin AA. Ultrafast Intraband Spectroscopy of Hot-Carrier Cooling in Lead-Halide Perovskites. ACS ENERGY LETTERS 2018; 3:2199-2205. [PMID: 30450410 PMCID: PMC6231231 DOI: 10.1021/acsenergylett.8b01227] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 08/21/2018] [Indexed: 05/06/2023]
Abstract
The rapid relaxation of above-band-gap "hot" carriers (HCs) imposes the key efficiency limit in lead-halide perovskite (LHP) solar cells. Recent studies have indicated that HC cooling in these systems may be sensitive to materials composition, as well as the energy and density of excited states. However, the key parameters underpinning the cooling mechanism are currently under debate. Here we use a sequence of ultrafast optical pulses (visible pump-infrared push-infrared probe) to directly compare the intraband cooling dynamics in five common LHPs: FAPbI3, FAPbBr3, MAPbI3, MAPbBr3, and CsPbBr3. We observe ∼100-900 fs cooling times, with slower cooling at higher HC densities. This effect is strongest in the all-inorganic Cs-based system, compared to the hybrid analogues with organic cations. These observations, together with band structure calculations, allow us to quantify the origin of the "hot-phonon bottleneck" in LHPs and assert the thermodynamic contribution of a symmetry-breaking organic cation toward rapid HC cooling.
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Affiliation(s)
- Thomas
R. Hopper
- Department
of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
| | - Andrei Gorodetsky
- Department
of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
| | - Jarvist M. Frost
- Department
of Materials, Imperial College London, London SW7 2AZ, United Kingdom
- Department
of Physics, Imperial College London, London SW7 2AZ, United Kingdom
- Department
of Physics, King’s College London, London WC2R 2LS, United Kingdom
| | - Christian Müller
- Institute
for High-Frequency Technology, Technische
Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
- InnovationLab, Speyerer Strasse 4, 69115 Heidelberg, Germany
| | - Robert Lovrincic
- Institute
for High-Frequency Technology, Technische
Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
- InnovationLab, Speyerer Strasse 4, 69115 Heidelberg, Germany
| | - Artem A. Bakulin
- Department
of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
- E-mail:
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70
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Tan H, Che F, Wei M, Zhao Y, Saidaminov MI, Todorović P, Broberg D, Walters G, Tan F, Zhuang T, Sun B, Liang Z, Yuan H, Fron E, Kim J, Yang Z, Voznyy O, Asta M, Sargent EH. Dipolar cations confer defect tolerance in wide-bandgap metal halide perovskites. Nat Commun 2018; 9:3100. [PMID: 30082722 PMCID: PMC6079062 DOI: 10.1038/s41467-018-05531-8] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 07/08/2018] [Indexed: 11/10/2022] Open
Abstract
Efficient wide-bandgap perovskite solar cells (PSCs) enable high-efficiency tandem photovoltaics when combined with crystalline silicon and other low-bandgap absorbers. However, wide-bandgap PSCs today exhibit performance far inferior to that of sub-1.6-eV bandgap PSCs due to their tendency to form a high density of deep traps. Here, we show that healing the deep traps in wide-bandgap perovskites-in effect, increasing the defect tolerance via cation engineering-enables further performance improvements in PSCs. We achieve a stabilized power conversion efficiency of 20.7% for 1.65-eV bandgap PSCs by incorporating dipolar cations, with a high open-circuit voltage of 1.22 V and a fill factor exceeding 80%. We also obtain a stabilized efficiency of 19.1% for 1.74-eV bandgap PSCs with a high open-circuit voltage of 1.25 V. From density functional theory calculations, we find that the presence and reorientation of the dipolar cation in mixed cation-halide perovskites heals the defects that introduce deep trap states.
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Affiliation(s)
- Hairen Tan
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada.
- National Laboratory of Solid State Microstructures, Collaborative Innovation Centre of Advanced Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, 210093, Nanjing, Jiangsu, China.
| | - Fanglin Che
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Mingyang Wei
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Yicheng Zhao
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Makhsud I Saidaminov
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Petar Todorović
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Danny Broberg
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Grant Walters
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Furui Tan
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
- Key Lab of Photovoltaic Materials, Department of Physics and Electronics, Henan University, 475004, Kaifeng, China
| | - Taotao Zhuang
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Bin Sun
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Zhiqin Liang
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Haifeng Yuan
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
- Department of Chemistry, KU Leuven, Celestijnenlaan 200 F, B-3001, Leuven, Belgium
| | - Eduard Fron
- Department of Chemistry, KU Leuven, Celestijnenlaan 200 F, B-3001, Leuven, Belgium
| | - Junghwan Kim
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Zhenyu Yang
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Oleksandr Voznyy
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
| | - Mark Asta
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Edward H Sargent
- Department of Electrical and Computer Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada.
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