Signatures of Coherent Phonon Transport in Ultralow Thermal Conductivity Two-Dimensional Ruddlesden–Popper Phase Perovskites

Christodoulides, Alexander D.; Guo, Peijun; Dai, Liyi; Hoffman, Justin M.; Li, Xiaotong; Zuo, Xiaobing; Rosenmann, Daniel; Brumberg, Alexandra; Kanatzidis, Mercouri G.; Schaller, Richard D.; Malen, Jonathan A.

doi:10.1021/acsnano.0c03595

Cited by 28 publications

(48 citation statements)

References 59 publications

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“…[31] Concerning vibrations across the bilayer structure, cross-plane coherent acoustic phonons have been also reported. [34,35] The organic layer determines the distortions of the inorganic layer, and thereby influences the optical and vibrational properties of the 2DLPs. [8,28,29,36] Vibrational bands related to the organic moieties that appear at higher frequencies can also impact the band edge emission process.…”

Section: Introductionmentioning

confidence: 99%

Correlating Symmetries of Low‐Frequency Vibrations and Self‐Trapped Excitons in Layered Perovskites for Light Emission with Different Colors

Lin

Dhanabalan

Biffi

et al. 2022

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self-trapping of excitons occurs due to local lattice deformations that are induced by the Coulomb-field of the electronhole pair itself. [13] Such STE formation is favored in distorted octahedra lattices, and was first observed in 2DLPs with (110)-oriented octahedra lattices, which have intrinsically a strongly corrugated structure. [14,15] With the use of specific organic cations that induce static distortions in the octahedra lattice, STE formation and broadband emission can also be observed from 2DLPs with the more typical (001) crystallographic orientation, [8,11,16] where out-of-plane distortions were identified as a critical structural property. [10] Recent theoretical studies elucidated that Jahn-Teller like lattice deformations lead to the effective formation of STEs, and confirmed that out-of-plane distortions result in more efficient STE emission. [17] The local lattice deformation related to the STE requires energy, and several works have investigated the energy barrier for STE formation in different layered perovskite systems. [5,7,13,18,19] It is common understanding that phonons are involved in the formation of STEs and their emission dynamics in 2DLPs, however the detailed mechanism is not clear. [20][21][22][23][24] In 3D perovskites, the electron-phonon coupling can be assigned to strong longitudinal-optical (LO) phonons and has been quantified by The soft hybrid organic-inorganic structure of two-dimensional layered perovskites (2DLPs) enables broadband emission at room temperature from a single material, which makes 2DLPs promising sources for solid-state white lighting, yet with low efficiency. The underlying photophysics involves self-trapping of excitons favored by distortions of the inorganic lattice and coupling to phonons, where the mechanism is still under debate. 2DLPs with different organic moieties and emission ranging from self-trapped exciton (STE)-dominated white light to blue band-edge photoluminescence are investigated. Detailed insights into the directional symmetries of phonon modes are gained using angle-resolved polarized Raman spectroscopy and are correlated to the temperature-dependence of the STE emission. It is demonstrated that weak STE bands at low-temperature are linked to in-plane phonons, and efficient room-temperature STE emission to more complex coupling to several phonon modes with out-of-plane components. Thereby, a unique view is provided into the lattice deformations and recombination dynamics that are key to designing more efficient materials.

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Section: Introductionmentioning

confidence: 99%

Correlating Symmetries of Low‐Frequency Vibrations and Self‐Trapped Excitons in Layered Perovskites for Light Emission with Different Colors

Lin

Dhanabalan

Biffi

et al. 2022

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“…At the same time, this material exhibited anisotropic thermal conductivity, which is not unexpected considering the fact that it is all-inorganic, while it has been shown that the orientational effects of bulky organic spacer cations significantly affect out-of-plane thermal conductivity and that complex interactions involving inorganic components and organic spacers can lead to comparable phonon group velocities in both directions for an organic–inorganic 2D MHPs such as BA 2 PbI 4 . In addition, it was shown that for quasi-2D BA 2 MA n ‑1 Pb n I 3 n +1 single crystals, very low κ values (below 0.1 W m –1 K –1 ) could be obtained for RP perovskite single crystals with n = 3–6 . While the thermal conductivities of these films were higher than in single crystals due to random orientation of the polycrystalline grains, higher n value quasi-2D single crystals are particularly promising due to reduced group velocities of coherent phonons as a consequence of band flattening in the phonon dispersion leading to reduced thermal conductivity .…”

Section: Thermoelectric Properties Of Metal Halide Perovskitesmentioning

confidence: 70%

“…As an example, Giri et al reported thermal conductivities of different 2D MHPs through experiments and simulations, where iso-BA 2 PbI 4 exhibited a theoretical thermal conductivity as low as 0.1 W m –1 K –1 . Thermal conductivities which are significantly lower than that of 3D perovskites have been reported to date for several 2D and quasi-2D MHPs, ,,, but it should be noted that there could be significant differences between the samples with same composition but different film preparation methods, and between thin films and single crystals.…”

Section: Thermoelectric Properties Of Metal Halide Perovskitesmentioning

confidence: 80%

“…The anisotropy of electrical properties in 2D and quasi-2D MHPs can be significant, while the anisotropy of thermal properties is not fully clear yet. Nevertheless, existing studies have shown that there is a difference in thermal conductivity between single crystals and thin films of the MHPs, as well as for quasi-2D MHP films with the same composition but with different preferential crystallographic orientations . However, very weak anisotropy has been reported for 2D perovskites with BA spacer cation .…”

Section: Experimental Methods and Challenges In Characterizing Thermo...mentioning

confidence: 99%

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Metal Halide Perovskites as Emerging Thermoelectric Materials

Ren

Djurišić

et al. 2021

ACS Energy Lett.

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In addition to the broadly anticipated use of metal halide perovskites in photovoltaics and light-emitting devices, they also hold a great promise as cost-effective thermoelectrics, as they may offer an ultra-low thermal conductivity combined with a high Seebeck coefficient. This Review summarizes the recent advances in theoretical analysis and experimental studies of the thermoelectric properties of these materials, with a particular focus on organic–inorganic (hybrid) halide perovskites and low-dimensional analogues. After a short introduction of figures of merits of thermoelectric materials, we consider measurement methods used to characterize thermoelectric materials and outline some difficulties in applying those methods to perovskites, since accurate measurements are essential for further progress of this emerging research area. We then outline in detail the current progress achieved in metal halide perovskite thermoelectrics and offer a detailed discussion of possible strategies to resolve the discrepancy between their high theoretically predicted ZT values (1–2 at room temperature) and still rather low (below 0.2) experimental values.

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“…Importantly, the VPVP provides direct information on the local temperature, which opens a possibility of spatiotemporal thermal imaging at both near-equilibrium and far-fromequilibrium conditions, the latter made possible by direct impulsive thermal stimulation of the targeted material with higher-energy MIR pulses than used in this work. We anticipate that the demonstrated VPVP technique can be employed for investigating thermal transport in disordered materials such as organic or polymeric semiconducting films, 49 metal-organic frameworks, 50 covalent organic frameworks, 51 biological materials, 52 and low-dimensional halide perovskites, [53][54][55][56] some of which may not be amenable to high-vacuum deposition of metallic transducers atop.…”

Section: Discussionmentioning

confidence: 99%

Time-resolved vibrational-pump visible-probe spectroscopy for thermal conductivity measurement of metal-halide perovskites

Dai

et al. 2022

Review of Scientific Instruments

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Understanding thermal transport at the microscale to the nanoscale is crucially important for a wide range of technologies ranging from device thermal management and protection systems to thermal-energy regulation and harvesting. In the past decades, non-contact optical methods, such as time-domain and frequency-domain thermoreflectance, have emerged as extremely powerful and versatile thermal metrological techniques for the measurement of material thermal conductivities. Here, we report the measurement of thermal conductivity of thin films of CH3NH3PbI3 (MAPbI3), a prototypical metal-halide perovskite, by developing a time-resolved optical technique called vibrational-pump visible-probe (VPVP) spectroscopy. The VPVP technique relies on the direct thermal excitation of MAPbI3 by femtosecond mid-infrared optical pump pulses that are wavelength-tuned to a vibrational mode of the material, after which the time dependent optical transmittance across the visible range is probed in the ns to the μs time window using a broadband pulsed laser. Using the VPVP method, we determine the thermal conductivities of MAPbI3 thin films deposited on different substrates. The transducer-free VPVP method reported here is expected to permit spectrally resolving and spatiotemporally imaging of the dynamic lattice temperature variations in organic, polymeric, and hybrid organic–inorganic semiconductors.

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Signatures of Coherent Phonon Transport in Ultralow Thermal Conductivity Two-Dimensional Ruddlesden–Popper Phase Perovskites

Cited by 28 publications

References 59 publications

Correlating Symmetries of Low‐Frequency Vibrations and Self‐Trapped Excitons in Layered Perovskites for Light Emission with Different Colors

Correlating Symmetries of Low‐Frequency Vibrations and Self‐Trapped Excitons in Layered Perovskites for Light Emission with Different Colors

Metal Halide Perovskites as Emerging Thermoelectric Materials

Time-resolved vibrational-pump visible-probe spectroscopy for thermal conductivity measurement of metal-halide perovskites

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