Regensburg 2010 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: Organic Electronics and Photovoltaics II
CPP 20.4: Vortrag
Dienstag, 23. März 2010, 14:30–14:45, H37
The Relationship between the Electric Field Induced Dissociation of Charge Transfer (CT) Excitons and the Photocurrent in Novel Hybrid Small Molecular/Polymeric Solar Cells — •Sahika Inal1, Alan Sellinger2, and Dieter Neher1 — 1Universität Potsdam, Institut für Physik und Astronomie, 14476 Potsdam-Golm — 2Institute of Materials Research & Engineering, Singapore 117602
Complete dissociation of coulombically bound interfacial states is an ultimate step accounting for photovoltaic performance. Recent work has proposed that the emission of CT-exciton, i.e. an exciplex, is a competing process to the generation of free charges [Appl. Phys. Lett. 2007, 90, 092117]. Here, we investigated the photophysical processes in a bulk heterojunction system using a soluble poly(p-phenylenevinylene) donor and a novel small molecular electron acceptor based on Vinazene (2-vinyl-4,5-dicyanoimidazole). Recent work has shown that this blend exhibits a featureless emission, prominent at long wavelengths of the spectrum, which was attributed to a CT-exciton [J. Chem. Phys. 2009, 130, 094703]. We monitored the field induced dissociation of these CT-excitons by means of steady state and time resolved PL spectroscopy. Shortened decay times and reduced PL emission in blend film evidence the dissociation of the emissive intermolecular pair by the external electric field. Analyzing the dependence of the photocurrent and external quantum efficiency on the external field, the fate of the separated exciplex pairs is tackled. It is suggested that the formation of free carriers involves channels other than CT-excitons in such blends.