Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 62: Poster II: Photovoltaics and Organic Semiconductors
HL 62.12: Poster
Donnerstag, 25. März 2010, 18:00–20:00, Poster D2
Charge Transfer States in Polymer:Fullerene Solar Cells — •Michael Binder1, Daniel Rauh2, Carsten Deibel1, and Vladimir Dyakonov1,2 — 1Julius-Maximilians-University of Würzburg, Institute of Physics, Experimental Physics VI, D-97074 Würzburg — 2Bavarian Centre for Applied Energy Research e.V. (ZAE Bayern), D-97074 Würzburg
In the field of organic photovoltaic power conversion efficiencies as high as 6% have been achieved. One of the key factors is a high exciton dissociation yield. It is crucial to understand the processes involved in charge carrier separation such as the relaxation of the exciton to the so called charge transfer state (CTS). A possibility to investigate those states is to measure the external quantum efficiency (EQE) of solar cells in the near-infrared region as shown by Vandewal et al [1]. With additional EQE measurement of diodes consisting only of the pure acceptor or donor we confirm that the CTS are solely found in donor/acceptor blend systems. The energies we determined from the charge transfer-tails can be directly linked to the open circuit voltage of the solar cell. We investigated the CTS for polythiophene:fullerene blends with varying electron acceptor strength. Furthermore we discuss their energy and magnitude in view of solar cell preparation conditions and the impact on the device performance.
[1] K. Vandewal et al. Adv. Funct. Mater. 2008,18, 2064--2070