Elucidating Batch-to-Batch Variation Caused by Homocoupled Side Products in Solution-Processable Organic Solar Cells

Tim Vangerven, Pieter Verstappen, Nilesh Patil, Jan D'Haen, Ilaria Cardinaletti, Johannes Benduhn, Niko Van Den Brande, Maxime Defour, Vincent Lemaur, David Beljonne, Roberto Lazzaroni, Benoit Champagne, Koen Vandewal, Jens W. Andreasen, Peter Adriaensens, Dag W. Breiby, Bruno Van Mele, Dirk Vanderzande, Wouter Maes, Jean Manca

Research output: Contribution to journalArticlepeer-review


Conjugated polymers and small molecules based on alternating electron-donating (D) and electron-accepting (A) building blocks have led to state-of-the-art organic solar cell materials governing efficiencies beyond 10%. Unfortunately, the connection of D and A building blocks via cross-coupling reactions does not always proceed as planned, which can result in the generation of side products containing D-D or A-A homocoupling motifs. Previous studies have reported a reduced performance in polymer and small molecule solar cells when such defect structures are present. A general consensus on the impact of homocouplings on device performance is, however, still lacking as is a profound understanding of the underlying causes of the device deterioration. For differentiating the combined effect of molecular weight and homocouplings in polymer solar cells, a systematic study on a small molecule system (DTS(FBBTh2)2) is presented. The impact of homocouplings on nanomorphology, thermal, and electro-optical properties is investigated. It is demonstrated that small quantities of homocouplings (<10%) already lead to suboptimal device performance, as this strongly impacts the molecular packing and electronic properties of the photoactive layer. These results highlight the importance of material purity and pinpoint homocoupling defects as one of the most probable reasons for batch-to-batch variations.

Original languageEnglish
Pages (from-to)9088-9098
Number of pages11
JournalChemistry of Materials
Issue number24
Publication statusPublished - 27 Dec 2016


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