Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 47: Organic Electronics and Photovoltaics: OPV I (jointly with CPP, HL, O)

TT 47.2: Vortrag

Dienstag, 17. März 2015, 14:30–14:45, C 130

Calculation of exciton dissociation rates in ordered and disordered 2D model organic photovoltaic interfaces — •Hector Vazquez¹ and Alessandro Troisi² — ¹Inst. of Physics, Academy of Sciences of the Czech Rep., CZ — ²Dept. of Chemistry and Centre of Scientific Computing, University of Warwick, UK

The efficient generation of free charges from incident light in organic photovoltaic cells has been studied extensively but is not yet well understood. In order to separate, electron and hole have to overcome the Coulomb attraction and several mechanisms have been proposed. In particular, 'hot' excitons having excess energy have received a lot of attention but no consensus yet exists [1].

In this talk, I will introduce a method to calculate exciton dissociation rates [2] and will describe its application to 2-Dimensional model organic photovoltaic interfaces. The method uses Green's functions within a widely applicable model Hamiltonian of donor/acceptor interfaces with and without disorder. Initial states are Frenkel excitons while final states are Charge-Transfer (CT) states. I will present results for the generation rates of CT states where I will highlight the importance of disorder and the delocalization of the excitonic wavefunctions. Excitons dissociate into 'hot' CT states with partially separated charges, where electron and hole are located far from the interface.

1) A. A. Bakulin et al., Science 335, 1340 (2012), A. E. Jailaubekov et al., Nat. Mater. 12 66 (2013), G. Grancini et al., Nat. Mater. 12 29 (2013), K. Vandewal et al., Nat. Mater. 13 63 (2013).

2) H. Vazquez, A. Troisi, Phys. Rev. B 88, 205304 (2013).