Unusually Strong Biexciton Repulsion Detected in Quantum Confined CsPbBr<sub>3</sub> Nanocrystals with Two and Three Pulse Femtosecond Spectroscopy

Dana, Jayanta; Binyamin, Tal; Etgar, Lioz; Ruhman, Sanford

doi:10.1021/acsnano.1c02123

Cited by 27 publications

(38 citation statements)

References 53 publications

(138 reference statements)

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“…However, the value of the BX binding energy in LHP NCs is a subject of current debate. Reported values for the prototypical all-inorganic CsPbBr 3 NCs span the range between strongly attractive to strongly repulsive interaction (ε b ≈ +100 meV 11 to −100 meV; 12 see Supporting Information Table S1 ). Common to all previous experimental works is their reliance on ensemble measurements.…”

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confidence: 99%

Resolving the Controversy in Biexciton Binding Energy of Cesium Lead Halide Perovskite Nanocrystals through Heralded Single-Particle Spectroscopy

et al. 2021

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Understanding exciton−exciton interaction in multiply excited nanocrystals is crucial to their utilization as functional materials. Yet, for lead halide perovskite nanocrystals, which are promising candidates for nanocrystal-based technologies, numerous contradicting values have been reported for the strength and sign of their exciton−exciton interaction. In this work, we unambiguously determine the biexciton binding energy in single cesium lead halide perovskite nanocrystals at room temperature. This is enabled by the recently introduced single-photon avalanche diode array spectrometer, capable of temporally isolating biexciton−exciton emission cascades while retaining spectral resolution. We demonstrate that CsPbBr 3 nanocrystals feature an attractive exciton−exciton interaction, with a mean biexciton binding energy of 10 meV. For CsPbI 3 nanocrystals, we observe a mean biexciton binding energy that is close to zero, and individual nanocrystals show either weakly attractive or weakly repulsive exciton−exciton interaction. We further show that, within ensembles of both materials, single-nanocrystal biexciton binding energies are correlated with the degree of charge-carrier confinement.

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Resolving the Controversy in Biexciton Binding Energy of Cesium Lead Halide Perovskite Nanocrystals through Heralded Single-Particle Spectroscopy

et al. 2021

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“…[24][25][26][27] The interpretation of the transient optical signals that convey the aforementioned relaxation processes in MHP-based materials must be taken with care, especially when pumping far above the bandgap and at high fluences. These conditions can favor a myriad of processes that obfuscate the intraband relaxation, including, but by no means limited to: interband transitions between distinct electronic/spin states, [28][29][30] exciton formation/dissociation, 13,[31][32][33] energy/charge migration, [34][35][36] bandgap renormalization, 21,37 refractive index changes, 21,38 Stark shifting, 39,40 and many-body (Auger) processes. 41 The interpretation is complicated further still by the lack of established analysis procedures for even the most widely used transient absorption (pump-probe, PP) methods.…”

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confidence: 99%

Multi-Pulse Terahertz Spectroscopy: Hot Polaron Photoconductivity Dynamics in Metal-Halide Perovskites

Zheng

Bakulin

2021

Physical Chemistry of Semiconductor Materials and Interfaces XX

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The behavior of hot carriers in metal-halide perovskites (MHPs) present a valuable foundation for understanding the details of carrier-phonon coupling in the materials as well as the prospective development of highly efficient hot carrier and carrier multiplication solar cells. Whilst the carrier population dynamics during cooling have been intensely studied, the evolution of the hot carrier properties, namely the hot carrier mobility, remain largely unexplored. To address this, we introduce a novel ultrafast visible pump -infrared push -terahertz probe spectroscopy (PPP-THz) to monitor the real-time conductivity dynamics of cooling carriers in methylammonium lead iodide. We find a decrease in mobility upon optically depositing energy into the carriers, which is typical of band-transport. Surprisingly, the conductivity recovery dynamics are incommensurate with the intraband relaxation measured by an analogous experiment with an infrared probe (PPP-IR), and exhibit a negligible dependence on the density of hot carriers. These results and the kinetic modelling reveal the importance of highly-localized lattice heating on the mobility of the hot electronic states. This collective polaron-lattice phenomenon may contribute to the unusual photophysics observed in MHPs and should be accounted for in devices that utilize hot carriers.

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“…24−27 The transient optical signals that convey the aforementioned relaxation processes in MHP-based materials must be interpreted with care, especially when pumping far above the bandgap and at high fluences. These conditions can favor a myriad of processes that obfuscate the intraband relaxation, including but by no means limited to interband transitions between distinct electronic/spin states, 28−30 exciton formation/dissociation, 13,31−33 bandgap renormalization, 21,37 refractive index changes, 21,38 Stark shifting, 39,40 and many-body (Auger) processes. 41 The interpretation is complicated further still by the lack of established analysis procedures for even the most widely used transient absorption [pump−probe (PP)] methods.…”

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confidence: 99%

Multipulse Terahertz Spectroscopy Unveils Hot Polaron Photoconductivity Dynamics in Metal-Halide Perovskites

Zheng

Hopper

Gorodetsky

et al. 2021

J. Phys. Chem. Lett.

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Hot carriers in metal-halide perovskites (MHPs) present a foundation for understanding carrier-phonon coupling in the materials as well as the prospective development of high-performance hot carrier photovoltaics. While the carrier population dynamics during cooling have been scrutinized, the evolution of the hot carrier properties, namely mobility, remains largely unexplored. Here we introduce novel ultrafast visible pump–infrared push–terahertz probe spectroscopy to monitor the real-time conductivity dynamics of cooling carriers in methylammonium lead iodide. We find a decrease in mobility upon optically re-exciting the carriers, as expected for band transport. Surprisingly, the conductivity recovery is incommensurate with the hot carrier population dynamics measured by infrared probe and exhibits a negligible dependence on the hot carrier density. Our results reveal the importance of localized lattice heating toward the hot carrier mobility. This collective polaron-lattice phenomenon may contribute to the unusual photophysics of MHPs and should be accounted for in hot carrier devices.

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Unusually Strong Biexciton Repulsion Detected in Quantum Confined CsPbBr₃ Nanocrystals with Two and Three Pulse Femtosecond Spectroscopy

Cited by 27 publications

References 53 publications

Resolving the Controversy in Biexciton Binding Energy of Cesium Lead Halide Perovskite Nanocrystals through Heralded Single-Particle Spectroscopy

Resolving the Controversy in Biexciton Binding Energy of Cesium Lead Halide Perovskite Nanocrystals through Heralded Single-Particle Spectroscopy

Multi-Pulse Terahertz Spectroscopy: Hot Polaron Photoconductivity Dynamics in Metal-Halide Perovskites

Multipulse Terahertz Spectroscopy Unveils Hot Polaron Photoconductivity Dynamics in Metal-Halide Perovskites

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Unusually Strong Biexciton Repulsion Detected in Quantum Confined CsPbBr3 Nanocrystals with Two and Three Pulse Femtosecond Spectroscopy

Cited by 27 publications

References 53 publications

Resolving the Controversy in Biexciton Binding Energy of Cesium Lead Halide Perovskite Nanocrystals through Heralded Single-Particle Spectroscopy

Resolving the Controversy in Biexciton Binding Energy of Cesium Lead Halide Perovskite Nanocrystals through Heralded Single-Particle Spectroscopy

Multi-Pulse Terahertz Spectroscopy: Hot Polaron Photoconductivity Dynamics in Metal-Halide Perovskites

Multipulse Terahertz Spectroscopy Unveils Hot Polaron Photoconductivity Dynamics in Metal-Halide Perovskites

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Unusually Strong Biexciton Repulsion Detected in Quantum Confined CsPbBr₃ Nanocrystals with Two and Three Pulse Femtosecond Spectroscopy