Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 45: Organic photovoltaics and electronics

HL 45.10: Talk

Thursday, March 15, 2018, 17:30–17:45, EW 203

Field-Assisted Charge Generation in PffBT4T-2OD:PC71BM Organic Solar Cells — •Andreas Weu¹, Tom Hopper², Artem Bakulin², and Yana Vaynzof¹ — ¹Centre for Advanced Materials, Universität Heidelberg — ²Department of Chemistry, Imperial College London

Although remarkable progress has been made in both synthesis of new organic materials and optimisation of processing procedures for organic solar cells, the principle process of photo-induced charge generation in donor:acceptor systems with low driving energy remains unclear. Here, we present a photophysical study of the high performance material system PffBT4T-2OD:PC71BM, which shows efficiencies ~11% despite having only minimal energy offset. We demonstrate by steady-state and ultra-fast optical techniques that the built-in field within a device structure is required for long-range charge separation, while in neat blend films an energetic barrier prevents exciton dissociation and charge transfer to the fullerene acceptor.[1] Our observations are likely to be applicable to other material systems with low driving energy and highlight the importance of using complete devices for photophysical studies.

[1] Andreas Weu, Thomas R. Hopper, Vincent Lami, Joshua A. Kress, Artem A. Bakulin and Yana Vaynzof, "Field-Assisted Charge Generation in Highly Efficient PffBT4T-2OD:Fullerene Organic Solar Cells", submitted to J. Phys. Chem. Lett.