Hot Carriers in Halide Perovskites: How Hot Truly?

Lim, Jia Wei Melvin; Giovanni, David; Righetto, Marcello; Feng, Minjun; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze Chien

doi:10.1021/acs.jpclett.0c00504

Cited by 54 publications

(85 citation statements)

References 46 publications

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“…Note that the extracted carrier temperature also depends on the choice of the region of interest. [27] However, our method shows robustness in the EPC calculation in spite of different reported fitting choices (details in Note S4, Supporting Information). Figure 1c shows the electron temperature dynamics in MAPbBr 3 at three pump excitation powers corresponding to carrier densities; 2.0, 5.0, and 8.5 × 10 18 cm -3 .…”

Section: Extraction Of Hot-carriermentioning

confidence: 99%

Uncovering the Electron‐Phonon Interplay and Dynamical Energy‐Dissipation Mechanisms of Hot Carriers in Hybrid Lead Halide Perovskites

Chan

Fan

Wang

et al. 2021

Advanced Energy Materials

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The discovery of slow hot carrier cooling in hybrid organic–inorganic lead halide perovskites (HOIPs) has provided exciting prospects for efficient solar cells that can overcome the Shockley–Queisser limit. Questions still loom over how electron‐phonon interactions differ from traditional polar semiconductors. Herein, the electron‐phonon coupling (EPC) strength of common perovskite films (MAPbBr3, MAPbI3, CsPbI3, and FAPbBr3) is obtained using transient absorption spectroscopy by analyzing the hot carrier cooling thermodynamics via a simplified two‐temperature model. Density function theory calculations are numerically performed at relevant electron‐temperatures to confirm experiments. Further, the variation of carrier‐temperature over a large range of carrier‐densities in HOIPs is analyzed, and an “S‐shaped” dependence of the initial carrier‐temperature to carrier‐density is reported. The phenomenon is attributed to the dominance of the large polaron screening and the destabilization effect which causes an increasing‐decreasing fluctuation in temperature at low excitation powers; and a hot‐phonon bottleneck which effectively increases the carrier temperature at higher carrier‐densities. The turning point in the relationship is indicative of the critical Mott density related to the nonmetal‐metal transition. The EPC analysis provides a novel perspective to quantify the energy transfer in HOIPs, electron‐lattice subsystem, and the complicated screening‐bottleneck interplay is comprehensively described, resolving the existing experimental contradictions.

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Section: Extraction Of Hot-carriermentioning

confidence: 99%

Uncovering the Electron‐Phonon Interplay and Dynamical Energy‐Dissipation Mechanisms of Hot Carriers in Hybrid Lead Halide Perovskites

Chan

Fan

Wang

et al. 2021

Advanced Energy Materials

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show abstract

“…S3), indicating the broadening from the GSB peak width does not substantially affect the extracted T c . Furthermore, we have extracted T c by fitting the whole TA spectra using the model described in (10,28) that considers Fermi-Dirac distribution of the carriers, broadening of the exciton and free carrier transitions, and bandgap renormalization effects ( fig. S4 and note S1B).…”

Section: Sample Characterizationsmentioning

confidence: 99%

Protecting hot carriers by tuning hybrid perovskite structures with alkali cations

et al. 2020

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Successful implementation of hot carrier solar cells requires preserving high carrier temperature as carriers migrate through the active layer. Here, we demonstrated that addition of alkali cations in hybrid organic-inorganic lead halide perovskites led to substantially elevated carrier temperature, reduced threshold for phonon bottleneck, and enhanced hot carrier transport. The synergetic effects from the Rb, Cs, and K cations result in ~900 K increase in the effective carrier temperature at a carrier density around 1018 cm−3 with an excitation 1.45 eV above the bandgap. In the doped thin films, the protected hot carriers migrate 100 s of nanometers longer than the undoped sample as imaged by ultrafast microscopy. We attributed these improvements to the relaxation of lattice strain and passivation of halide vacancies by alkali cations based on x-ray structural characterizations and first principles calculations.

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“…Since the effective mass of holes is similar to that of electrons 30 , we assume that the occupation probability of holes in the valence band is symmetric to that of electrons in the conduction band. Compared to fits of the entire TA bleach region [31][32] , Eqn. 3 only uses four fitting parameters, namely Rb, ∆Ebgr, Ef and Te, owing to the intrinsic independence of the broadening function.…”

Section: Transient Absorption Spectra -Analysis Of the High-energy Tail Of The Photobleachmentioning

confidence: 99%

Ultrafast photo-induced enhancement of electron-phonon coupling in metal-halide perovskites

Laquai¹,

Wang²,

Gao³

et al. 2021

Preprint

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In metal-halide perovskites (MHPs), the nature of organic cations affects both, the perovskite’s structure and its optoelectronic properties. Using ultrafast pump-probe spectroscopy, we demonstrate that in state-of-the-art mixed-cation MHPs ultrafast photo-induced bandgap narrowing occurs, and linearly depends on the excited carrier density in the range from 1016 cm− 3 to above 1018 cm− 3. Furthermore, time-domain terahertz (td-THz) photoconductivity measurements reveal that the majority of carriers are localized and that the localization increases with the carrier density. Both observations, the bandgap narrowing and carrier localization, can be rationalized by ultrafast (sub-2ps) photo-induced enhancement of electron-phonon coupling, originating from dynamic disorder, as clearly evidenced by the presence of a Debye relaxation component in the terahertz photoconductivity spectra. The observation of photo-induced enhancement of electron-phonon coupling and dynamic disorder not only provides specific insight into the polaron-strain distribution of excited states in MHPs, but also adds to the development of a concise picture of the ultrafast physics of this important class of semiconductors.

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Hot Carriers in Halide Perovskites: How Hot Truly?

Cited by 54 publications

References 46 publications

Uncovering the Electron‐Phonon Interplay and Dynamical Energy‐Dissipation Mechanisms of Hot Carriers in Hybrid Lead Halide Perovskites

Uncovering the Electron‐Phonon Interplay and Dynamical Energy‐Dissipation Mechanisms of Hot Carriers in Hybrid Lead Halide Perovskites

Protecting hot carriers by tuning hybrid perovskite structures with alkali cations

Ultrafast photo-induced enhancement of electron-phonon coupling in metal-halide perovskites

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