Visualizing morphological principles for efficient photocurrent generation in organic non-fullerene acceptor blends

02 juillet 2020 par Super Administrateur
Voici un article Frenchy dans Energy Environmental Science qui est issue d’un travail de collaboration entre l'Université de Heidelberg, CINaM, IM2NP et Fraunhofer ISE.

The efficiency of organic solar cells with donor polymers and non-fullerene acceptors depends on a complex morphology. Similar chemical and electronic structures impede generating in-depth insights in morphological details. We visualise molecular arrangements and the nanomorphology in PBDB-T:ITIC blends by correlating transmission electron micrographs and material distribution maps. Material phases are identified by machine learning on hyperspectral data from electron spectroscopic imaging. We observe a specific polymorph of ITIC after thermal annealing. During annealing, enhanced by the presence of additives, PBDB-T acts as nucleation site for ITIC due to strong p–p-interactions of the electron withdrawing groups of both molecules. This leads to efficient charge transport paths in ITIC phases with direct p–p-contact to PBDB-T at the interface. We conclude that p–p-stacking between donor and acceptor molecules facilitates charge carrier generation within mixed interface regions.

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