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O: Fachverband Oberflächenphysik

O 24: Organic Electronics and Photovoltaics I (jointly with CPP, DS, HL)

O 24.2: Vortrag

Montag, 11. März 2013, 17:30–17:45, H32

Direct Observation of Charge Separation in Perylene Monoimide Solid State Dye-Sensitized Solar Cells — •Ian Howard¹, Michael Meister¹, Björn Baumeier¹, Henrike Wonnenberger¹, Neil Pschirer², Rüdiger Sens², Ingmar Brüder², Klaus Müllen¹, Denis Andrienko¹, and Frédéric Laquai¹ — ¹Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany — ²BASF SE

Combining Vis-NIR broadband pump-probe transient absorption spectroscopy with precise measurement of the time-resolved photoinduced Stark effect we demonstrate that it is possible to track not only the rate of charge injection but also the motion of carriers after injection on the critical nanosecond timescale in Solid State Dye Sensitized Solar Cells. In terms of solar cell efficiency our findings have two major impacts. Firstly, we directly observe that the *reductive quenching* pathway previously suggested (wherein a photoexcited dye donates a hole to the hole transport material before then injecting an electron, now from the dye anion state, into the TiO2) is important for obtaining high device efficiencies, especially for NIR absorbing dyes which exhibit a reduced driving force for electron injection directly from the dye exciton. Secondly, we find that many charges return to the interface after following injection, likely due to Coulombic and image charge effects. Screening the charges better, for example by reducing the dielectric contrast or increasing the dye length, should decrease the interfacial charge density and thereby parasitic recombination.