Hole dynamics in a photovoltaic donor-acceptor couple revealed by simulated time-resolved X-ray absorption spectroscopy

IF 2.3 2区物理与天体物理 Q3 CHEMISTRY, PHYSICAL

Structural Dynamics-Us Pub Date : 2019-07-01 DOI:10.1063/1.5097653

Khadijeh Khalili, L. Inhester, C. Arnold, R. Welsch, J. W. Andreasen, R. Santra

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引用次数: 10

Abstract

Theoretical and experimental methodologies that can characterize electronic and nuclear dynamics, and the coupling between the two, are needed to understand photoinduced charge transfer in molecular building blocks used in organic photovoltaics. Ongoing developments in ultrafast pump-probe techniques such as time-resolved X-ray absorption spectroscopy, using an X-ray free electron laser in combination with an ultraviolet femtosecond laser, present desirable probes of coupled electronic and nuclear dynamics. In this work, we investigate the charge transfer dynamics of a donor-acceptor pair, which is widely used as a building block in low bandgap block copolymers for organic photovoltaics. We simulate the dynamics of the benzothiadiazole-thiophene molecule upon photoionization with a vacuum ultraviolet (VUV) pulse and study the potential of probing the subsequent charge dynamics using time-resolved X-ray absorption spectroscopy. The photoinduced dynamics are calculated using on-the-fly nonadiabatic molecular dynamics simulations based on Tully's Fewest Switches Surface Hopping approach. We calculate the X-ray absorption spectrum as a function of time after ionization at the Hartree-Fock level. The changes in the time-resolved X-ray absorption spectrum at the sulfur K-edge reveal the ultrafast charge carrier dynamics in the molecule occurring on a femtosecond time scale. These theoretical findings anticipate that ultrafast time-resolved X-ray absorption spectroscopy using an X-ray probe in combination with a VUV pump offers a new approach to investigate the detailed dynamics of organic photovoltaic materials.

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用模拟时间分辨X射线吸收光谱揭示光伏施主-受主对中的空穴动力学

要理解用于有机光伏发电的分子构件中的光诱导电荷转移，需要能够表征电子和核动力学以及两者之间耦合的理论和实验方法。超快泵浦探测技术的持续发展，如时间分辨x射线吸收光谱，使用x射线自由电子激光器与紫外飞秒激光器相结合，提供了理想的耦合电子和核动力学探针。在这项工作中，我们研究了一个供体-受体对的电荷转移动力学，它被广泛用于有机光伏电池的低带隙嵌段共聚物。我们模拟了苯并噻唑-噻吩分子在真空紫外(VUV)脉冲光电离时的动力学，并研究了利用时间分辨x射线吸收光谱探测后续电荷动力学的潜力。利用基于Tully最小开关表面跳变方法的动态非绝热分子动力学模拟计算了光致动力学。我们计算了电离后在Hartree-Fock能级的x射线吸收光谱作为时间的函数。硫k边的时间分辨x射线吸收谱的变化揭示了分子中发生在飞秒时间尺度上的超快载流子动力学。这些理论发现预示着使用x射线探针与VUV泵相结合的超快时间分辨x射线吸收光谱为研究有机光伏材料的详细动力学提供了一种新的方法。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Structural Dynamics-Us CHEMISTRY, PHYSICALPHYSICS, ATOMIC, MOLECU-PHYSICS, ATOMIC, MOLECULAR & CHEMICAL

CiteScore

5.50

自引率

3.60%

发文量

审稿时长

16 weeks

期刊介绍： Structural Dynamics focuses on the recent developments in experimental and theoretical methods and techniques that allow a visualization of the electronic and geometric structural changes in real time of chemical, biological, and condensed-matter systems. The community of scientists and engineers working on structural dynamics in such diverse systems often use similar instrumentation and methods. The journal welcomes articles dealing with fundamental problems of electronic and structural dynamics that are tackled by new methods, such as: Time-resolved X-ray and electron diffraction and scattering, Coherent diffractive imaging, Time-resolved X-ray spectroscopies (absorption, emission, resonant inelastic scattering, etc.), Time-resolved electron energy loss spectroscopy (EELS) and electron microscopy, Time-resolved photoelectron spectroscopies (UPS, XPS, ARPES, etc.), Multidimensional spectroscopies in the infrared, the visible and the ultraviolet, Nonlinear spectroscopies in the VUV, the soft and the hard X-ray domains, Theory and computational methods and algorithms for the analysis and description of structuraldynamics and their associated experimental signals. These new methods are enabled by new instrumentation, such as: X-ray free electron lasers, which provide flux, coherence, and time resolution, New sources of ultrashort electron pulses, New sources of ultrashort vacuum ultraviolet (VUV) to hard X-ray pulses, such as high-harmonic generation (HHG) sources or plasma-based sources, New sources of ultrashort infrared and terahertz (THz) radiation, New detectors for X-rays and electrons, New sample handling and delivery schemes, New computational capabilities.