Deciphering hot- and multi-exciton dynamics in core–shell QDs by 2D electronic spectroscopies

Righetto, Marcello; Bolzonello, Luca; Volpato, Andrea; Amoruso, Giordano; Panniello, Annamaria; Fanizza, Elisabetta; Striccoli, Marinella; Collini, Elisabetta

doi:10.1039/c8cp02574f

Cited by 30 publications

(50 citation statements)

References 64 publications

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“…The PB signal by σ + probe would originate from SE of excitons from IS to ground state (i.e., Δ m J = + 1), while the PA signal by σ – probe originates from further absorption of the trapped excitons in IS to upper energy state (i.e., Δ m J = –1). This upper state is tentatively assigned to either the bound biexcitonic 29 state or the Γ 1 – state from C -band 17 . Filling of these traps would then cause saturation of the σ – (i.e., counter-circular) PA signal, as observed in Fig.…”

Section: Resultsmentioning

confidence: 97%

Ultrafast long-range spin-funneling in solution-processed Ruddlesden–Popper halide perovskites

et al. 2019

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Room-temperature spin-based electronics is the vision of spintronics. Presently, there are few suitable material systems. Herein, we reveal that solution-processed mixed-phase Ruddlesden–Popper perovskite thin-films transcend the challenges of phonon momentum-scattering that limits spin-transfer in conventional semiconductors. This highly disordered system exhibits a remarkable efficient ultrafast funneling of photoexcited spin-polarized excitons from two-dimensional (2D) to three-dimensional (3D) phases at room temperature. We attribute this efficient exciton relaxation pathway towards the lower energy states to originate from the energy transfer mediated by intermediate states. This process bypasses the omnipresent phonon momentum-scattering in typical semiconductors with stringent band dispersion, which causes the loss of spin information during thermalization. Film engineering using graded 2D/3D perovskites allows unidirectional out-of-plane spin-funneling over a thickness of ~600 nm. Our findings reveal an intriguing family of solution-processed perovskites with extraordinary spin-preserving energy transport properties that could reinvigorate the concepts of spin-information transfer.

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Section: Resultsmentioning

confidence: 97%

Ultrafast long-range spin-funneling in solution-processed Ruddlesden–Popper halide perovskites

et al. 2019

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“…As shown in Figure 1(a), only the red portion of the lowest 1S energy band is covered by the exciting laser profile, and therefore the 2D maps are dominated by a diagonal signal corresponding to the ground state bleaching (GSB) and stimulated emission (SE) of this transition. [24][25][26][27] The population dynamics along t2 have been analyzed through a multi complex-exponential global fitting methodology, 28,29 revealing a three-exponential behavior. The kinetic constants and their amplitude distribution are in agreement with previous reports on the ultrafast dynamics of CdSe QDs, confirming the reliability of the data.…”

Section: Mainmentioning

confidence: 99%

“…31,32 In the regions of the 2D map in the proximity of the diagonal-peak ( Figures 2(b, d)), the oscillating dynamics is dominated by the longitudinal optical (LO) phonon with a beating frequency of about 200 cm -1 , whose presence has been already characterized in several CdSe QDs samples. 24,27,30,33,34 The dephasing dynamics of this phonon mode and its coupling with electronic degrees of freedom has been the focus of several theoretical and experimental investigations, and it is still under scrutiny. [35][36][37][38][39] However, it affects the coherent dynamics on timescales much longer than the one investigated here.…”

Section: )mentioning

confidence: 99%

“…This signal distribution is consistent with what has already been observed in CdSe QDs' solutions. 24,25,30,40,41 Similarly, the diagonal signals are attributed to GSB and SE signals of the 1S and 2S intra-dot transitions, while the cross-peak features originate from the associated state-filling process. 25 Instead, when only 1S is excited, the maps are fully analogous to the ones reported in Figure 2(a) for the S-QD sample, confirming the common origin of the relaxation dynamics for all samples in the ultrafast timescale.…”

Section: Figure 2 2des Measurements On S-qd Sample (A) Evolution Ofmentioning

confidence: 99%

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Room Temperature Inter-Dot Coherent Dynamics in Multilayers Quantum Dot Materials

Collini

Gattuso²,

Kolodny³

et al. 2020

Preprint

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<div><div><div><p>The full blossoming of quantum technologies requires the availability of easy-to-prepare materials where quantum coherences can be effectively initiated, controlled and exploited, preferably at ambient conditions. Solid-state multilayers of colloidally grown quantum dots (QDs) are highly promising for this task because of the possibility of assembling networks of electronically coupled QDs through the modulation of sizes, inter-dot linkers and distances. To usefully probe coherence in these materials, the dynamical characterization of their collective quantum mechanically coupled states is needed. Here we explore by 2D electronic spectroscopy the coherent dynamics of solid-state multilayers of electronically coupled colloidally grown CdSe QDs and complement it by detailed computations. The time evolution of a coherent superposition of states delocalized over more than one QD was captured at ambient conditions. We thus provide important evidence for inter-dot coherences in such solid-state materials, opening up the effective exploitation of these materials towards quantum technologies.</p></div></div></div>

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“…The observed two-step relaxation process and the associated time scales are in agreement with previous works on spherical CdSe NPs. 32 , 33 …”

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Visualizing Ultrafast Electron Transfer Processes in Semiconductor–Metal Hybrid Nanoparticles: Toward Excitonic–Plasmonic Light Harvesting

et al. 2021

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Recently, it was demonstrated that charge separation in hybrid metal–semiconductor nanoparticles (HNPs) can be obtained following photoexcitation of either the semiconductor or of the localized surface plasmon resonance (LSPR) of the metal. This suggests the intriguing possibility of photocatalytic systems benefiting from both plasmon and exciton excitation, the main challenge being to outcompete other ultrafast relaxation processes. Here we study CdSe-Au HNPs using ultrafast spectroscopy with high temporal resolution. We describe the complete pathways of electron transfer for both semiconductor and LSPR excitation. In the former, we distinguish hot and band gap electron transfer processes in the first few hundred fs. Excitation of the LSPR reveals an ultrafast (<30 fs) electron transfer to CdSe, followed by back-transfer from the semiconductor to the metal within 210 fs. This study establishes the requirements for utilization of the combined excitonic–plasmonic contribution in HNPs for diverse photocatalytic applications.

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Deciphering hot- and multi-exciton dynamics in core–shell QDs by 2D electronic spectroscopies

Abstract: 2D electronic spectroscopy maps acquired in different configurations unveil intraband hot carrier cooling and interband multi-exciton recombination dynamics.

Cited by 30 publications

References 64 publications

Ultrafast long-range spin-funneling in solution-processed Ruddlesden–Popper halide perovskites

Ultrafast long-range spin-funneling in solution-processed Ruddlesden–Popper halide perovskites

Room Temperature Inter-Dot Coherent Dynamics in Multilayers Quantum Dot Materials

Visualizing Ultrafast Electron Transfer Processes in Semiconductor–Metal Hybrid Nanoparticles: Toward Excitonic–Plasmonic Light Harvesting

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