Light Emission from CsPbBr<sub>3</sub> Metal Halide Perovskite Nanocrystals Arises from Dual Emitting States with Distinct Lattice Couplings

Strandell, Dallas P.; Kambhampati, Patanjali

doi:10.1021/acs.nanolett.3c03975

Cited by 6 publications

(6 citation statements)

References 47 publications

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“…The MHP NC were synthesized by two different methods. The 15 nm NC were synthesized by a variation of the initial Kovalenko method, which we have previously described in detail for the synthesis and the spectroscopy. ,− ,,,− The other sizes of MHP NC were synthesized by a more recent method by Kovalenko . The CdSe NC was commercially obtained from NN-Laboratories.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Hot Excitons Cool in Metal Halide Perovskite Nanocrystals as Fast as CdSe Nanocrystals

Strandell,

Zenatti,

Nagpal

et al. 2023

ACS Nano

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The idea of phonon bottlenecks has long been pursued in nanoscale materials for their application in hot exciton devices, such as photovoltaics. Decades ago, it was shown that there is no quantum phonon bottleneck in strongly confined quantum dots due to their physics of quantum confinement. More recently, it was proposed that there are hot phonon bottlenecks in metal halide perovskites due to their physics. Recent work has called into question these bottlenecks in metal halide perovskites. Here, we compare hot exciton cooling in a range of sizes of CsPbBr3 nanocrystals from weakly to strongly confined. These results are compared to strongly confined CdSe quantum dots of two sizes and degrees of quantum confinement. CdSe is a model system as a ruler for measuring hot exciton cooling being fast, by virtue of its efficient Auger-assisted processes. By virtue of 3 ps time resolution, the hot exciton photoluminescence can now be directly observed, which is the most direct measure of the presence of hot excitons and their lifetimes. The hot exciton photoluminescence decays on nearly the same 2 ps time scale on both the weakly confined perovskite and the larger CdSe quantum dots, much faster than the 10 ps cooling predicted by transient absorption experiments. The smaller CdSe quantum dot has still faster cooling, as expected from quantum size effects. The quantum dots of perovskites show extremely fast hot exciton cooling, decaying faster than detection limits of <1 ps, even faster than the CdSe system, suggesting the efficiency of Auger processes in these metal halide perovskite nanocrystals and especially in their quantum dot form. These results across a range of sizes of nanocrystals reveal extremely fast hot exciton cooling at high exciton density, independent of composition, but dependent upon size. Hence these metal halide perovskite nanocrystals seem to cool heavily following quantum dot physics.

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Section: Experimental Methodsmentioning

confidence: 99%

“…The CdSe NC was commercially obtained from NN-Laboratories. The t-PL measurements were performed on an optically triggered streak camera detection system (Axis Photonique) that has a measured instrument response function of better than 3 ps. ,,, The details are in the SI.…”

Section: Experimental Methodsmentioning

confidence: 99%

Hot Excitons Cool in Metal Halide Perovskite Nanocrystals as Fast as CdSe Nanocrystals

Strandell,

Zenatti,

Nagpal

et al. 2023

ACS Nano

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“…While SE contributes with the same sign as the bleach (negative OD), it is red shifted both by XX and by Stokes shifting due to lattice relaxation. 45 In the case of x()…”

Section: X Vs Xxmentioning

confidence: 99%

Spectator exciton effects in nanocrystals III: Unveiling the stimulated emission cross section in quantum confined CsPbBr3 nanocrystals

De,

Bhunia,

Cai

et al. 2024

Preprint

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Quantifying stimulated emission in semiconductor nanocrystals (NCs) remains challenging due to masking of its effects on pump-probe spectra by excited state absorption and ground state bleaching signals. Absence of this defining photo-physical parameter in turn impedes assignment of band edge electronic structure in many of these important fluorophores. Here we employ a generally applicable 3-pulse ultrafast spectroscopic method coined the “Spectator Exciton” (SX) approach to measure stimulated-emission efficiency in quantum confined inorganic perovskite CsPbBr3 NCs, band edge electronic structure of which is the subject of lively ongoing debate. Our results show that in 5-6 nm CsPbBr3 NCs, a single exciton bleaches more than half of the intense band edge absorption band, while the cross section for stimulated emission from the same state is nearly 6 times weaker. Discussion of these findings in light of several recent electronic structure models for this material proves them unable of simultaneously explaining both measures. proving the importance of this new input to resolving this debate. Along with femtosecond time resolved photoluminescence measurements on the same sample, SX results also verifies that biexciton interaction energy is intensely attractive with a magnitude of ~80 meV. In light of this observation, our previous suggestion that bi-exciton interaction is repulsive is reassigned to hot phonon induced slowdown of carrier relaxation leading to direct Auger recombination from an excited state. The mechanism behind the extreme slowing of carrier cooling after several stages of exciton recombination remains to be determined.

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“…However, the photogenerated electrons and holes partly lose their energy by so-called phonon emission via carrier–phonon coupling at an ultrafast time scale, , thereby limiting the actual utilization efficiency of charge carriers. More importantly, the consequent lattice heating effects can alter the intrinsic optical characteristics of the material and complicate their transient spectral responses, − making it challenging to resolve and quantify the electronic and thermal contributions in time-resolved signals, not to mention their temporal evolutions.…”

Section: Introductionmentioning

confidence: 99%

Disentangling Thermal from Electronic Contributions in the Spectral Response of Photoexcited Perovskite Materials

Wang,

Nughays,

Rossi

et al. 2024

J. Am. Chem. Soc.

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Disentangling electronic and thermal effects in photoexcited perovskite materials is crucial for photovoltaic and optoelectronic applications but remains a challenge due to their intertwined nature in both the time and energy domains. In this study, we employed temperature-dependent variable-angle spectroscopic ellipsometry, density functional theory calculations, and broadband transient absorption spectroscopy spanning the visible to mid-to-deep-ultraviolet (UV) ranges on MAPbBr 3 thin films. The use of deep-UV detection opens a new spectral window that enables the exploration of high-energy excitations at various symmetry points within the Brillouin zone, facilitating an understanding of the ultrafast responses of the UV bands and the underlying mechanisms governing them. Our investigation reveals that the photoinduced spectral features remarkably resemble those generated by pure lattice heating, and we disentangle the relative thermal and electronic contributions and their evolutions at different delay times using combinations of decay-associated spectra and temperature-induced differential absorption. The results demonstrate that the photoinduced transients possess a significant thermal origin and cannot be attributed solely to electronic effects. Following photoexcitation, as carriers (electrons and holes) transfer their energy to the lattice, the thermal contribution increases from ∼15% at 1 ps to ∼55% at 500 ps and subsequently decreases to ∼35−50% at 1 ns. These findings elucidate the intricate energy exchange between charge carriers and the lattice in photoexcited perovskite materials and provide insights into the limited utilization efficiency of photogenerated charge carriers.

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Light Emission from CsPbBr₃ Metal Halide Perovskite Nanocrystals Arises from Dual Emitting States with Distinct Lattice Couplings

Cited by 6 publications

References 47 publications

Hot Excitons Cool in Metal Halide Perovskite Nanocrystals as Fast as CdSe Nanocrystals

Hot Excitons Cool in Metal Halide Perovskite Nanocrystals as Fast as CdSe Nanocrystals

Spectator exciton effects in nanocrystals III: Unveiling the stimulated emission cross section in quantum confined CsPbBr3 nanocrystals

Disentangling Thermal from Electronic Contributions in the Spectral Response of Photoexcited Perovskite Materials

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Light Emission from CsPbBr3 Metal Halide Perovskite Nanocrystals Arises from Dual Emitting States with Distinct Lattice Couplings

Cited by 6 publications

References 47 publications

Hot Excitons Cool in Metal Halide Perovskite Nanocrystals as Fast as CdSe Nanocrystals

Hot Excitons Cool in Metal Halide Perovskite Nanocrystals as Fast as CdSe Nanocrystals

Spectator exciton effects in nanocrystals III: Unveiling the stimulated emission cross section in quantum confined CsPbBr3 nanocrystals

Disentangling Thermal from Electronic Contributions in the Spectral Response of Photoexcited Perovskite Materials

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Product

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Light Emission from CsPbBr₃ Metal Halide Perovskite Nanocrystals Arises from Dual Emitting States with Distinct Lattice Couplings