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.
organic electronics
polimorphism
non-fullerene acceptors
organic solar cells
organic semiconductors
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
Institute of Material Science of Barcelona (ICMAB)
Amaia Iturrospe
Centro de Física de Materiales (CSIC-UPV/EHU)
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
Centro de Física de Materiales (CSIC-UPV/EHU)
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
Institute of Material Science of Barcelona (ICMAB)
Christian Müller
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Daniele Cangialosi
Centro de Física de Materiales (CSIC-UPV/EHU)
Natalie Stingelin
Georgia Institute of Technology
University of Bordeaux
Jaime Martin
Basque Foundation for Science (Ikerbasque)
University of A Coruña
University of the Basque Country (UPV/EHU)
Advanced Functional Materials
1616-301X (ISSN) 16163028 (eISSN)
Vol. 31 29 2103784Subject Categories
Materials Chemistry
Other Physics Topics
Condensed Matter Physics
DOI
10.1002/adfm.202103784