Understanding Batch-to-Batch Variations of Push-Pull Type Conjugated Polymers for Organic Photovoltaics

Wouter Maes^a, Omar Beckers^a, Koen Vandewal^a, Pieter Verstappen^a

^aHasselt University, Institute for Materials Research (IMO-IMOMEC), Wetenschapspark, 1, Diepenbeek, Belgium

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#OPV19. Organic Photovoltaics: recent breakthroughs, advanced characterization and modelling

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Jörg Ackermann and Uli Würfel

Invited Speaker, Wouter Maes, presentation 028
DOI: https://doi.org/10.29363/nanoge.nfm.2019.028
Publication date: 18th July 2019

Donor-acceptor or push-pull type conjugated polymers have become a dominating class of active materials in the field of organic electronics. Their adjustable light-harvesting, charge transfer and charge transport characteristics have been beneficially applied in organic photovoltaics, photodetectors and thin-film transistors. The conventional synthetic approach towards these push-pull polymers is based on Suzuki or (mostly) Stille cross-coupling of complementary functionalized heterocyclic precursors. In the ideal world, this should give rise to a perfect alternation of the employed building blocks throughout the polymer backbone and this alternation of electron rich (donor/push) and electron deficient (acceptor/pull) moieties leads to a substantial decrease of the bandgap. In recent years, however, it has become increasingly clear that the ‘real’ structure of the resulting alternating copolymers is often quite different from the projected one. Structural imperfections can for instance result from homocoupling of two identical building blocks. Furthermore, the end groups of these donor-acceptor copolymers are often also not those expected or targeted. In this contribution, recent results from our group will be presented, providing insights on the impact of homocoupling ‘defects’ on the device characteristics of organic solar cells. Additionally, different types of end groups were identified via MALDI-TOF mass spectrometry.

References:

[1] Pirotte, G.; Verstappen, P.; Vanderzande, D.; Maes, W. On the ‘True’ Structure of Push-Pull Type Low Bandgap Polymers for Organic Electronics. Adv. Electron. Mater. 2018, 1700481.

[2] Vangerven, T.; Verstappen, P.; Patil, N.; D’Haen, J.; Cardinaletti, I.; Benduhn, J.; Van den Brande, N.; Defour, M.; Lemaur, V.; Beljonne, D.; Lazzaroni, R.; Champagne, B.; Vandewal, K.; Andreasen, J. W.; Adriaensens, P.; Breiby, D. W.; Van Mele, B.; Vanderzande, D.; Maes, W.; Manca, J. Elucidating Batch-to-batch Variation Caused by Homocoupled Side Products in Solution Processable Organic Solar Cells. Chem. Mater. 2016, 28, 9088–9098.

[3] Vangerven, T.; Verstappen, P.; Drijkoningen, J.; Dierckx, W.; Himmelberger, S.; Salleo, A.; Vanderzande, D.; Maes, W.; Manca, J. V. Molar Mass versus Polymer Solar Cell Performance: Highlighting the Role of Homocouplings. Chem. Mater. 2015, 27, 3726–3732.

Acknowledgements:

The authors thank Hasselt University and the Research Foundation – Flanders (FWO Vlaanderen) for continuous financial support.

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