Dresden 2017 – wissenschaftliches Programm
CPP 41.9: Vortrag
Mittwoch, 22. März 2017, 17:30–17:45, ZEU 260
On the Role of Triplet Excitons in Organic Solar Cells — •Andreas Sperlich1, Stefan Väth1, Hannes Kraus1, and Vladimir Dyakonov1,2 — 1Experimental Physics VI, Julius Maximilian University of Würzburg, 97074 Würzburg — 2Bayerisches Zentrum für Angewandte Energieforschung (ZAE Bayern), 97074 Würzburg
A strategy for increasing the conversion efficiency of organic photovoltaics has been to increase VOC by tuning the energy levels of donor and acceptor components. However, this opens up a new loss pathway from an interfacial charge transfer state (CTS) to a donor triplet exciton (TE) state called electron back transfer (EBT), which is detrimental to device performance. To test this hypothesis, we study triplet formation in high performing blends of the fullerene PC70BM with either the polymer PTB7  or the soluble small molecule p-DTS(FBTTh2)2  and determine the impact of the morphology-optimizing additive 1,8-diiodoctane (DIO). Using photoluminescence and spin-sensitive optically and electrically detected magnetic resonance (ODMR, EDMR) measurements we find that TE formation does not only depend on the materials’ energetics, but also on temperature and nano-morphology. Furthermore, we observe TEs in real devices under realistic working conditions even for the most efficient solar cells, which has implications not only for efficiency, but also for devices stability.
 H. Kraus, et al., Sci. Reps. 6, 29158 (2016)
 S. Väth, et al., Adv. Energy Mater., doi: 10.1002/aenm.201602016 (2016)