Polymorphism in Non-Fullerene Acceptors Based on Indacenodithienothiophene
Journal article, 2021
Organic solar cells incorporating non-fullerene acceptors (NFAs) have reached remarkable power conversion efficiencies of over 18%. Unlike fullerene derivatives, NFAs tend to crystallize from solutions, resulting in bulk heterojunctions that include a crystalline acceptor phase. This must be considered in any morphology-function models. Here, it is confirmed that high-performing solution-processed indacenodithienothiophene-based NFAs, i.e., ITIC and its derivatives ITIC-M, ITIC-2F, and ITIC-Th, exhibit at least two crystalline forms. In addition to highly ordered polymorphs that form at high temperatures, NFAs arrange into a low-temperature metastable phase that is readily promoted via solution processing and leads to the highest device efficiencies. Intriguingly, the low-temperature forms seem to feature a continuous network that favors charge transport despite of a poorly order along the pi-pi stacking direction. As the optical absorption of the structurally more disordered low-temperature phase can surpass that of the more ordered polymorphs while displaying comparable-or even higher-charge transport properties, it is argued that such a packing structure is an important feature for reaching highest device efficiencies, thus, providing guidelines for future materials design and crystal engineering activities.
polimorphism
organic solar cells
organic semiconductors
organic electronics
non-fullerene acceptors
Author
Sara Marina
University of the Basque Country (UPV/EHU)
Alberto D. Scaccabarozzi
Istituto Italiano di Tecnologia
King Abdullah University of Science and Technology (KAUST)
Edgar Gutierrez-Fernandez
University of the Basque Country (UPV/EHU)
Eduardo Solano
ALBA Synchrotron Light Facility
Aditi Khirbat
Georgia Institute of Technology
Laura Ciammaruchi
Spanish National Research Council (CSIC)
Amaia Iturrospe
Spanish National Research Council (CSIC)
Alex Balzer
Georgia Institute of Technology
Liyang Yu
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Elena Gabirondo
University of the Basque Country (UPV/EHU)
Xavier Monnier
Donostia International Physics Center
Spanish National Research Council (CSIC)
Haritz Sardon
University of the Basque Country (UPV/EHU)
Thomas D. Anthopoulos
King Abdullah University of Science and Technology (KAUST)
Mario Caironi
Istituto Italiano di Tecnologia
Mariano Campoy-Quiles
Spanish National Research Council (CSIC)
Christian Müller
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Daniele Cangialosi
Spanish National Research Council (CSIC)
Natalie Stingelin
University of Bordeaux
Georgia Institute of Technology
Jaime Martin
University of the Basque Country (UPV/EHU)
University of A Coruña
Basque Foundation for Science (Ikerbasque)
Advanced Functional Materials
1616-301X (ISSN) 16163028 (eISSN)
Vol. 31 29 2103784Subject Categories (SSIF 2011)
Materials Chemistry
Other Physics Topics
Condensed Matter Physics
DOI
10.1002/adfm.202103784