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EP02.05.05 : Thermally Stable Polymer—Fullerene Solar Cells Using Bisazide Crosslinkers

9:45 AM–10:00 AM Apr 4, 2018

PCC North, 200 Level, Room 222 BC

Description
Dominik Landerer1 Christian Sprau1 Daniel Baumann1 Patrick Pingel2 Hartmut Krüger2 Silvia Janietz2 Alexander Colsmann1

1, Karlsruhe Institute of Technology, Karlsruhe, , Germany
2, Fraunhofer Institute for Applied Polymer Research, Potsdam, , Germany


After enhancing the power conversion efficiencies of organic solar cells beyond 10%, their long term stability has become the most urgent challenge in order to eventually integrate organic solar cells into end-user products. Solar devices may have to endure harsh conditions already during the fabrication of tiles or façade elements, typically requiring lamination temperatures up to 120°C, critical for the initial performance of organic solar modules.
In this work, we demonstrate polymer:fullerene bulk-heterojunctions with significantly enhanced thermal stability at 120°C and beyond, by incorporating a novel crosslinkable bisazide that can lock the bulk-heterojunction morphology. The bisazide molecule is easy to synthesize and offers large-scale accessibility.
The solar cells clearly outperform the thermal stability of reference devices without the crosslinking bisazides.
We investigated bulk-heterojunctions comprising a variety of light-harvesting copolymers, combined with the industrially relevant fullerene acceptor PC61BM. Upon thermal annealing, the reference blends without the crosslinking bisazides exhibit only moderate thermal stability and loose more than 70% of their initial performance, mainly originating from crystallization and aggregation of the fullerene. In contrast, polymer:fullerene blends comprising 7wt.% bisazide crosslinkers show effectively no degradation but retain their initial performance: Even after 200 hours of continuous thermal annealing at 120°C, the respective solar cells still exhibit over 90% of their initial performance.

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