Direct Observation of Electron–Phonon Coupling and Slow Vibrational Relaxation in Organic–Inorganic Hybrid Perovskites

Straus, Daniel B.; Parra, Sebastian Hurtado; Iotov, Natasha; Gebhardt, Julian; Rappe, Andrew M.; Subotnik, Joseph E.; Kikkawa, James M.; Kagan, Cherie R.

doi:10.1021/jacs.6b08175

Cited by 218 publications

(434 citation statements)

References 41 publications

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“…99.7% of the excitonic photoluminescence (PL) is emitted out of the lowest-lying excited state at 15 K. However, 0.3% of the PL is emitted out of discrete higher energy resonances that also appear at similar energies in the absorption spectrum, each separated by ~40 meV from the lowest-lying resonance and from one another. 5 The existence of hot PL violates Kasha's rule, which states carriers relax to the lowest-lying excited state before fluorescing. 7 PL from these higher-energy resonances competes with relaxation to the lowestlying excited state, and the kinetics combined with the regular spacing of the resonances led us to hypothesize that we observed a phonon progression.…”

Section: Toc Graphicmentioning

confidence: 99%

Tailoring Hot Exciton Dynamics in 2D Hybrid Perovskites through Cation Modification

et al. 2020

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We report a family of two-dimensional hybrid perovskites (2DHPs) based on phenethylammonium lead iodide ((PEA)2PbI4) that show complex structure in their lowtemperature excitonic absorption and photoluminescence (PL) spectra as well as hot exciton PL.We replace the 2-position (ortho) H on the phenyl group of the PEA cation with F, Cl, or Br to systematically increase the cation's cross-sectional area and mass and study changes in the excitonic structure. These single atom substitutions substantially change the observable number of and spacing between discrete resonances in the excitonic absorption and PL spectra and drastically increase the amount of hot exciton PL that violates Kasha's rule by over an order of magnitude. To fit the progressively larger cations, the inorganic framework distorts and is strained, reducing the Pb-I-Pb bond angles and increasing the 2DHP band gap. Correlation between the 2DHP structure and steady-state and time-resolved spectra suggests the complex structure of resonances arises from one or two manifolds of states, depending on the 2DHP Pb-I-Pb bond angle (as)symmetry, and the resonances within a manifold are regularly spaced with an energy separation that decreases as the mass of the cation increases. The uniform separation between resonances and the dynamics that show excitons can only relax to the next-lowest state are consistent with a vibronic progression caused by a vibrational mode on the cation. These

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Section: Toc Graphicmentioning

confidence: 99%

Tailoring Hot Exciton Dynamics in 2D Hybrid Perovskites through Cation Modification

et al. 2020

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“…[12,37] It was demonstrated that electron-phonon coupling in (C 4 H 9 NH 3 ) 2 PbI 4 is dominated by homopolar optical phonons through deformation potential, while the contribution from acoustic phonon and longitudinal optical phonons (Fröhlich coupling) are negligible. [12,37] It was demonstrated that electron-phonon coupling in (C 4 H 9 NH 3 ) 2 PbI 4 is dominated by homopolar optical phonons through deformation potential, while the contribution from acoustic phonon and longitudinal optical phonons (Fröhlich coupling) are negligible.…”

Section: Doi: 101002/adom201700373mentioning

confidence: 99%

Van Der Waals Hybrid Perovskite of High Optical Quality by Chemical Vapor Deposition

Chen

Wang

Sun

et al. 2017

Advanced Optical Materials

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Among different structures, two extreme cases are of special interest: (1) when m goes to infinity, a complete 3D structure is formed due to the absence of larger alkyl amine ligands, e.g., CH 3 NH 3 PbI 3 ; [4] (2) when m goes to 1, smaller alkyl groups are absent and a complete 2D structure is formed where each single layer of lead halide octahedrons is separated by large alkyl groups, i.e., (RNH 3 ) 2 PbX 4 . [5] A finite m value which exceeds unity will lead to multilayers of lead halide octahedrons in each individual inorganic slab, e.g., (C 4 H 9 NH 3 ) 2 (CH 3 NH 3 ) 3 Pb 4 I 13 . [8] At present, most of the successful devices are based on 3D perovskites, e.g., CH 3 NH 3 PbX 3 , whose long carrier recombination lifetime, long diffusion length, and high carrier mobility make them promising for photovoltaic applications. [3] In comparison, 2D perovskites will not only inherit most of the aforementioned advantages of 3D perovskites but also possess the superiorities of other 2D materials (transitional metal dichalcogenides (TMDCs) and graphene), e.g., high in-plane carrier mobility [9] and easiness in exfoliation or transfer. [10,11] These advantages make them competitive candidates for high-speed transistors, heterostructures, or planar photodetectors. Figure 1b showed the polyhedron model of a typical 2D perovskite (C 4 H 9 NH 3 ) 2 PbI 4 where each layer of inorganic octahedrons (drawn grey) is sandwiched between two layers of organic butylamine ligands. As illustrated in Figure 1c, this unique AB stacking of organic-inorganic layers provides a natural quantum well structure where charge carriers are localized within inorganic layers due to the insulating organic ligands. The dielectric confinement and quantum confinement effect both enhance the charge carrier localization such that exciton binding energy amounts to several hundred meV, leading to observable excitonic effect even at room temperature. [10,[12][13][14] In addition, when integrated with 3D perovskites, 2D perovskites serve as protection layers and enhances the moisture stability of the system. [8] These promising properties have attracted intensive investigations into (RNH 3 ) 2 PbX 4 with various organic ligands (R ranging from C 4 H 9  to C 12 H 25  and other aromatic compounds) [13,[15][16][17] and halide elements (usually Br and I). [15,17] The great potential of (RNH 3 ) 2 PbX 4 is being rapidly revealed, as witnessed by its recent success in solar cells, light-emitting diodes (LEDs), and photodetectors. [8,9,18,19] 2D hybrid perovksite (RNH 3 ) 2 PbX 4 materials not only serve as ideal platforms to study fundamental physics such as polariton dynamics but also show promise for optoelectronic and electro-optic applications. However, for the preparation of high optical quality crystals, mechanical exfoliation has to be applied in the past. In this work, the vapor phase growth of single crystalline (C 4 H 9 NH 3 ) 2 PbI 4 flakes with high optical quality is reported. Individual single crystalline domains show lateral size about 5-10 µm w...

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“…Thesame decay behaviors also confirm the absence of Auger combination process at the present experiment condition. We ascribe the first ultrafast component to the cooling of the hot STE states, [28][29][30][31] identified by the blue shifting of the excited state absorption of (C 8 NH 12 ) 4 BiBr 7 ·H 2 Oa ts hort decay times ( Figure S10d). It is notable that the STE absorption of (C 8 NH 12 ) 4 Bi 0.57 Sb 0.43 Br 7 ·H 2 Oi sm uch broader than that of (C 8 NH 12 ) 4 BiBr 7 ·H 2 O, indicating new STEs are generated.…”

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confidence: 94%

Air‐Stable, Lead‐Free Zero‐Dimensional Mixed Bismuth‐Antimony Perovskite Single Crystals with Ultra‐broadband Emission

et al. 2019

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Lead-free zero-dimensional (0D) organic-inorganic metal halide perovskites have recently attracted increasing attention for their excellent photoluminescence properties and chemical stability.Here,wereport the synthesis and characterization of an air-stable 0D mixed metal halide perovskite (C 8 NH 12 ) 4 Bi 0.57 Sb 0.43 Br 7 ·H 2 O, in whichi ndividual [BiBr 6 ] 3À and [SbBr 6 ] 3À octahedral units are completely isolated and surrounded by the large organic cation C 8 H 12 N + .U pon photoexcitation, the bulk crystals exhibit ultra-broadband emission ranging from 400 to 850 nm, which originates from both free excitons and self-trapped excitons.T his is the first example of 0D perovskites with broadband emission spanning the entire visible spectrum. In addition, (C 8 NH 12 ) 4 Bi 0.57 Sb 0.43 Br 7 ·H 2 Oe xhibits excellent humidity and light stability.T hese findings present an ew direction towards the design of environmentally-friendly,h igh-performance 0D perovskite light emitters.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Direct Observation of Electron–Phonon Coupling and Slow Vibrational Relaxation in Organic–Inorganic Hybrid Perovskites

Cited by 218 publications

References 41 publications

Tailoring Hot Exciton Dynamics in 2D Hybrid Perovskites through Cation Modification

Tailoring Hot Exciton Dynamics in 2D Hybrid Perovskites through Cation Modification

Van Der Waals Hybrid Perovskite of High Optical Quality by Chemical Vapor Deposition

Air‐Stable, Lead‐Free Zero‐Dimensional Mixed Bismuth‐Antimony Perovskite Single Crystals with Ultra‐broadband Emission

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