Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Organic Semiconductors

CPP 8.25: Poster

Monday, March 14, 2011, 17:30–19:30, P2

External and internal quantum efficiency determination of small molecule organic tandem solar cells — •Ronny Timmreck, André Merten, David Wynands, Jan Meiss, Wolfgang Tress, Karl Leo, and Moritz Riede — Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden, Germany

Measuring external quantum efficiency (EQE) is an important method for characterizing solar cells. In addition to its relevance for the spectral mismatch correction of solar cells, it yields deep insight into different physical processes in solar cells because many different measurement parameters can be varied independently. Hence, especially for organic solar cells it is an important technique to get a better understanding of the underlying physics.

We perform systematic studies of the EQE of single and tandem heterojunction organic solar cells by varying the wavelength and intensity of the bias illumination. Furthermore, the bias voltage that is applied to the solar cell during measurement is varied such that for every working point of the solar cell IV-characteristics an EQE spectrum can be obtained. Both requires the use of lock-in techniques for detecting the current response of the solar cell to the chopped monochromatic light on top of the bias illumination.

Our results show a strong influence of the bias voltage on the EQE-spectrum implying that optimization of organic solar cells should be done considering EQE at maximum power point and not short-circuit. With our measurements, it is furthermore possible to independently determine the IV-characteristics of the subcells of a tandem solar cell.