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Monahan NR, Williams KW, Kumar B, et al. Direct Observation of Entropy-Driven Electron-Hole Pair Separation at an Organic Semiconductor Interface. Phys Rev Lett. 2015;114(24):247003doi: 10.1103/PhysRevLett.114.247003.
Monahan, N. R., Williams, K. W., Kumar, B., Nuckolls, C., & Zhu, X. Y. (2015). Direct Observation of Entropy-Driven Electron-Hole Pair Separation at an Organic Semiconductor Interface. Physical review letters, 114(24), 247003. https://doi.org/10.1103/PhysRevLett.114.247003
Monahan, Nicholas R, et al. "Direct Observation of Entropy-Driven Electron-Hole Pair Separation at an Organic Semiconductor Interface." Physical review letters vol. 114,24 (2015): 247003. doi: https://doi.org/10.1103/PhysRevLett.114.247003
Monahan NR, Williams KW, Kumar B, Nuckolls C, Zhu XY. Direct Observation of Entropy-Driven Electron-Hole Pair Separation at an Organic Semiconductor Interface. Phys Rev Lett. 2015 Jun 19;114(24):247003. doi: 10.1103/PhysRevLett.114.247003. Epub 2015 Jun 16. PMID: 26196998.
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Phys Rev Lett. 2015 Jun 19;114(24):247003. doi: 10.1103/PhysRevLett.114.247003. Epub 2015 Jun 16.

Direct Observation of Entropy-Driven Electron-Hole Pair Separation at an Organic Semiconductor Interface.

Physical review letters

Nicholas R Monahan, Kristopher W Williams, Bharat Kumar, Colin Nuckolls, X-Y Zhu

Affiliations

  1. Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA.

PMID: 26196998 DOI: 10.1103/PhysRevLett.114.247003

Abstract

How an electron-hole pair escapes the Coulomb potential at a donor-acceptor interface has been a key issue in organic photovoltaic research. Recent evidence suggests that long-distance charge separation can occur on ultrafast time scales, yet the underlying mechanism remains unclear. Here we use charge transfer excitons (CTEs) across an organic semiconductor-vacuum interface as a model and show that nascent hot CTEs can spontaneously climb up the Coulomb potential within 100 fs. This process is driven by entropic gain due to the rapid rise in density of states with increasing electron-hole separation. In contrast, the lowest CTE cannot delocalize, but undergoes self-trapping and recombination.

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