- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Spectrally Resolved Ultrafast Exciton Transfer in Mixed Perovskite Quantum Wells
摘要： Solution-processed perovskite quantum wells have been used to fabricate increasingly efficient and stable optoelectronic devices. Little is known about the dynamics of photogenerated excitons in perovskite quantum wells within the first few hundred femtoseconds – a crucial timescale on which energy and charge transfer processes may compete. Here we use ultrafast transient absorption and two-dimensional electronic spectroscopy to clarify the movement of excitons and charges in reduced-dimensional perovskite solids. We report excitonic funneling from strongly to weakly confined perovskite quantum wells within 150 fs, facilitated by strong spectral overlap and orientational alignment among neighboring wells. This energy transfer happens on timescales orders of magnitude faster than charge transfer, which we find to occur instead over 10 - 100s of picoseconds. Simulations of both F?rster-type interwell exciton transfer and free carrier charge transfer are in agreement with these experimental findings, with theoretical exciton transfer calculated to occur in 100s of fs.
关键词： energy transfer,Carrier,metal halide perovskite,two-dimensional electronic spectroscopy,layered perovskite,dynamics
更新于2025-09-23 15:23:52
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Generation of Ultrabroadband Phase-Locked Pulse Pairs in the Ultraviolet by Achromatic SHG
摘要： Two-dimensional electronic spectroscopy (2DES) is a powerful spectroscopic technique for the study of dynamics in coupled multi-chromophore systems, which has been successfully applied in the visible and infrared ranges. Its extension to the UV range (2DUV) is extremely promising for the study of biomolecules but poses several technical challenges: (i) the requirement of phase-locked pulse pairs; (ii) generation of extremely broadband UV pulses; (iii) dispersion management for the UV range. Here we present a setup able to generate ultrabroad phase-locked UV pump pulses with bandwidth from 260 to 310 nm. The UV pump pulse pairs are generated by Achromatic Second Harmonic Generation (ASHG) of a phase-locked, visible pulse pair (Fig. 1(a)). A non-collinear optical parametric amplifier (NOPA) produces 10-μJ, <6-fs-pulses in the 500-640 nm range. Two delayed, phase-locked replicas of the visible pulses are then generated by TWINS [1], a compact ultrastable interferometer consisting of a sequence of β-BBO birefringent wedges that allows varying with extreme accuracy and up to 1 ps the delay between the two replicas. The broadband visible replicas are subsequently chirped in a 45-mm block of SF57 and frequency doubled to the UV range by ASHG [2]. In this scheme, the visible pulse is dispersed by a fused silica (FS) prism and the angular dispersion is converted to a lateral dispersion by a second prism. The resulting collimated beam is focused into a 300-μm β-BBO crystal for SHG. By suitably choosing the prism separation (152 cm) and the focal length (35 mm) we match the propagation direction of each component with its SHG phase-matching angle.
关键词： ultrabroadband UV pulses,UV range,Two-dimensional electronic spectroscopy,Achromatic Second Harmonic Generation,phase-locked pulse pairs
更新于2025-09-12 10:27:22
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Excitonic Effects in Single Layer MoS <sub/>2</sub> Probed by Broadband Two-Dimensional Electronic Spectroscopy
摘要： Atomically thin Transition-metal dichalcogenides (TMDs) have come into the spotlight in optoelectronics thanks to their outstanding physical properties. In single-layer (1L) TMDs strong quantum confinement effects cause a weak screening of Coulomb, so that the excitons created by photo-excitation have large binding energy, up to several hundred meVs. While the steady-state properties of TMDCs have been studied in detail by linear optical techniques, the recent application of time-resolved nonlinear spectroscopy (mainly ultrafast pump-probe) has enabled the study of excited-state dynamics on femtosecond timescales opening up questions about the mechanisms of exciton relaxations and exciton-exciton interactions. Among TMDs, the spectrum of 1L MoS2 is characterized by two peaks of excitonic nature in the visible spectral region (1.9 eV and 2.05 eV), the so-called A and B excitons. They arise from optical transitions between the spin?orbit split top valence band and the bottom conduction band, around K and K’. Here we use two-dimensional electronic spectroscopy (2DES) to track the sub-ps excitonic interactions within 1L MoS2. We report 2DES measurements obtained on a chemical vapor deposition grown 1L MoS2 sample, at 77K, using sub 20-fs broadband pulses. Thanks to its unique combination of high temporal and spectral resolution, 2DES provides a series of excitation/detection correlation energy maps at different delays T, simultaneously covering the A and B excitons.
关键词： excitonic effects,MoS2,Transition-metal dichalcogenides,two-dimensional electronic spectroscopy
更新于2025-09-12 10:27:22
-
Coherent multidimensional spectroscopy of dilute gas-phase nanosystems
摘要： Two-dimensional electronic spectroscopy (2DES) is one of the most powerful spectroscopic techniques with unique sensitivity to couplings, coherence properties and real-time dynamics of a quantum system. While successfully applied to a variety of condensed phase samples, high precision experiments on isolated systems in the gas phase have been so far precluded by insufficient sensitivity. However, such experiments are essential for a precise understanding of fundamental mechanisms and to avoid misinterpretations. Here, we solve this issue by extending 2DES to isolated nanosystems in the gas phase prepared by helium nanodroplet isolation in a molecular beam-type experiment. This approach uniquely provides high flexibility in synthesizing tailored, quantum state-selected model systems of single and many-body character. In a model study of weakly-bound Rb2 and Rb3 molecules we demonstrate the method’s unique capacity to elucidate interactions and dynamics in tailored quantum systems, thereby also bridging the gap to experiments in ultracold quantum science.
关键词： Two-dimensional electronic spectroscopy,helium nanodroplet isolation,gas-phase nanosystems,ultracold quantum science,Rb2 and Rb3 molecules
更新于2025-09-10 09:29:36
-
Simulating Fluorescence Detected Two-Dimensional Electronic Spectroscopy of Multi-Chromophoric Systems
摘要： We present a theory for modeling fluorescence detected two-dimensional electronic spectroscopy of multichromophoric systems. The theory is tested by comparison of the predicted spectra of the light-harvesting complex LH2 with experimental data. A qualitative explanation of the strong cross-peaks as compared to conventional two-dimensional electronic spectra is given. The strong cross-peaks are attributed to the clean ground state signal that is revealed when the annihilation of exciton pairs created on the same LH2 complex cancels oppositely-signed signals from the doubly-excited state. This annihilation process occurs much faster than the non-radiative relaxation. Furthermore, the lineshape difference is attributed to slow dynamics, exciton delocalization within the bands and intraband exciton-exciton annihilation. This is in line with existing theories presented for model systems. We further propose the use of time-resolved fluorescence detected two-dimensional spectroscopy to study state resolved exciton-exciton annihilation.
关键词： fluorescence detected two-dimensional electronic spectroscopy,multichromophoric systems,light-harvesting complex LH2,exciton-exciton annihilation,time-resolved fluorescence detected two-dimensional spectroscopy
更新于2025-09-04 15:30:14
-
[Topics in Current Chemistry Collections] Multidimensional Time-Resolved Spectroscopy || Electronic Couplings in (Bio-) Chemical Processes
摘要： During the last two decades, 2D optical techniques have been extended to the visible range, targeting electronic transitions. Since the report of the very first 2D electronic measurement (Hybl et al. in J Chem Phys 115:6606–6622, [2001]), two-dimensional electronic spectroscopy (2DES) has allowed fundamentally new insights into the structure and dynamics of condensed-phase systems (Ginsberg et al. in Acc Chem Res 42:1352–1363, 2009; Jonas in Annu Rev Phys Chem 54:425–463, 2003), producing experiments that measure correlations among electronic states of an absorbing species within complex systems. 2DES is used to investigate photophysical phenomena involving electronic or vibrational couplings in multi-chromophoric systems [energy transfer in photosynthesis is one great example of how 2DES can disentangle various energy transfer pathways (Brixner et al. in Nature 625–628, 2005; Engel et al. in Nature 446:782–786, 2007; Collini et al. in Nature 463:644–647, 2010)], but also ultrafast photochemical processes in which the tracked molecules change permanently or are heterogeneous (Ruetzel et al. in Proc Natl Acad Sci 111:4764–4769, 2014; Consani et al. in Science 339:1586–1589, 2013). We divide this chapter according to some of the major areas that have been established thanks to 2DES in the following fields: heterogeneity of systems, excitation energy transfer mechanisms, photo-induced coherent oscillations associated with electronic and vibrational couplings, and complex chemical reactions (Fig. 1).
关键词： Energy transfer,Vibronic coupling,Two-dimensional electronic spectroscopy,Photoreactivity,Heterogeneity
更新于2025-09-04 15:30:14