Early charge separation events in light-harvesting materials

MPSD Seminar

Datum: 28.07.2016
Uhrzeit: 14:00 - 15:00
Vortragende(r): Carlo Andrea Rozzi
Instituto Nanoscienze Consiglio Nazionale Delle Ricerche (CNR NANO S3), Modena
Ort: CFEL (Bldg. 99)
Raum: Seminar Room V, O1.109
Gastgeber: Angel Rubio

The photoinduced charge-separation events occurring in photovoltaic and light harvesting systems have traditionally been interpreted in terms of the incoherent kinetics of optical excitations and of charge hopping. Although signatures of quantum coherence were recently observed in energy transfer in photosynthetic bacteria andalgae[1] still very little is known about the role of quantum coherence at room temperature in technologically relevant organic photovoltaic materials. Recent experiments found evidence for an ultrafast long-range charge separation in such systems but could not differentiate between coherent and incoherent charge-transfermodels.[2]

By combining TDDFT simulations of the quantum dynamics and high time resolution femtosecond spectroscopy, we provide evidence that the coherent coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer both in covalently bonded molecules[2] and in non-bonded bulk heterojunctions[3]. We have exploited the results of our research to design, syntesize and characterize a novel molecular scaffold for photovoltaic applications[4].

References:
[1] G. S. Engel et al. Nature 446, 782–786 (2007)
[2] S. Gélinas et al., Science 343, 512–516 (2014)
[3] C. A. Rozzi et al., Nat. Commun. 4, 1602 (2013)
[4] S. Falke et al., Science 344, 1001 (2014)
[5] S. Pittalis et al., Adv. Funct. Mater. 25, 2047–2053 (2014)