Berlin 2015 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 7: Organic photovoltaics and electronics - mostly properties of the absorber (jointly with CPP,DS)
DS 7.7: Vortrag
Montag, 16. März 2015, 18:30–18:45, EW 202
Mobility Relaxation in PTB7:PC70BM on nanosecond timescale — •Andreas Fritze1, Andreas Sperlich1, Carsten Deibel2, and Vladimir Dyakonov1,3 — 1Experimental Physics VI, Julius Maximilian University of Würzburg, 97074 Würzburg — 2Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz — 3ZAE Bayern, 97074 Würzburg
For photovoltaics, charge carrier lifetime is an essential parameter due to its influence on short circuit current, and thus on power conversion efficiency. In organic photovoltaics, for several material systems, charge carrier lifetime exceeds predictions from recombination models by orders of magnitude. In literature, this phenomenon is discussed in the context of reduced langevin recombination, for instance the high-efficiency bulk heterojunction polymer fullerene solar cell PTB7:PC70BM, it is shown that recombination is also reduced. However, the physical processes responsible for these low recombination rates, such as mobility relaxation, energetic traps, and morphological traps, are hard to observe separately. Here, we present simultaneous transient absorption (TA) and transient microwave conductivity (TRMC) measurements on PTB7:PC70BM films. From the experimental data we calculate time dependent mobility, since TA is sensitive to charge carrier density and TRMC is sensitive to conductivity. A relaxation of mobility on these time scales is measured the first time separately. Thus, we can distinguish mobility relaxation from other recombination influencing processes in PTB7:PC70BM.