Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 61: Organic Electronics and Photovoltaics I (jointly with CPP, DS, and HL)
O 61.11: Talk
Thursday, March 14, 2013, 12:30–12:45, H34
Electroabsorption spectroscopy on organic pin solar cells — •Ellen Siebert-Henze, Vadim G. Lyssenko, Janine Fischer, Karl Leo, and Moritz Riede — Institut für Angewandte Photophysik, George-Bähr-Str. 1, Dresden, Germany
The built-in voltage has a significant impact on the solar cell performance, but its origins are controversially discussed. In our work we determine the built-in voltage of small molecule organic solar cells based on the pin concept by electroabsorption spectroscopy (EA).
EA detects the change in absorption caused by an electrical field (Stark effect). A change in DC bias on the device results in a variation of the Stark signal. It is probed adding an AC voltage on top of the DC bias enabling the detection using a lock-in amplifier. Thus, the information about the built-in voltage can be evaluated.
As a model system, flat heterojunction solar cells containing C60 as acceptor and MeO-TPD as donor material are investigated. The doping concentration of both the hole and the electron transport layer is modified and it is shown that there is an influence of the consequential change of their work functions on the built-in voltage. Both the short-circuit current as well as the fill factor increase for larger built-in voltages.