Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 58: Focus Session: Structure and Transport in Organic Photovoltaics III (jointly with CPP)

HL 58.1: Vortrag

Mittwoch, 28. März 2012, 15:00–15:15, ER 270

(contribution withdrawn) Many-body perturbation theory calculations for organic photovoltaics — •Carina Faber, Claudio Attaccalite, and Xavier Blase — Institut Néel, CNRS, Grenoble, France

We evaluate the performance of ab initio GW calculations for ionization energies (IEs) and for HOMO-LUMO gaps of thirteen gas phase molecules of interest for organic electronic and photovoltaics, including e.g. pentacene and free-base porphyrins. Our calculations are based on an efficient Gaussian-basis implementation of GW with explicit treatment of the dynamical screening through contour deformation techniques. We show that we significantly improve the IEs and gaps as compared to DFT Kohn-Sham results. Moreover, we study within the GW and Bethe-Salpeter approach the low lying singlet charge-transfer excitations in molecular donor/ acceptor complexes associating benzene, naphtalene and anthracene derivatives with the TCNE acceptor. Our calculations demonstrate that such techniques can reproduce the experimental data with a mean absolute error of 0.1-0.15 eV for the present set of dimers, which is in excellent agreement with the best time-dependent density functional studies with optimized range-separated functionals. The present results pave the way for the study of photoinduced charge-transfer processes in photovoltaic devices with a parameter-free ab initio approach showing equivalent accuracy for finite and extended systems. Finally, we show in the case of C60 that the magnitude of the electron-phonon coupling, an important quantity that governs the mobility of carriers in organic systems, is much better described within GW as compared to standard DFT calculations.