Yueling Su, Lu Zhang, Zicheng Ding,* Yi Zhang, Yin Wu, Yuwei Duan, Qiang Zhang,

Jidong Zhang, Yanchun Han, Zijian Xu, Rui Zhang,* Kui Zhao,

and Shengzhong (Frank) Liu*

ABSTRACT:

The single bulk-heterojunction active layer based on non-fullerene acceptors
(NFAs) has dominated the power conversional efficiencies above 18% in
state-of-the-art organic solar cells (OSCs). However, a deep understanding
of the relationship between charge carrier process and film microstructure
remains unclear for emerging NFA OSCs. Herein, with the superstar PM6:Y6
blend as a model, the charge generation process in active layers is successfully manipulated by designing three different film microstructures, and they
are correlated with the final photovoltaic performance in OSC devices. The
amount of intermediate intra-moiety excited states from the nanoscale Y6
aggregates can be effectively enhanced by controlling the phase separation
domains and film crystallinity in the bicontinuous PM6:Y6 networks. This
robustly improves the hole transfer, and thus promotes charge generation.
As a result, the optimal films show superior device performance, that is, the
high efficiencies of 16.53% and 17.98% for PM6:Y6- and D18:Y6-based single
junction OSCs, respectively. The results presented here give a rational guide
for optimizing the charge carrier process through controlling morphological
microstructures toward high-performance NFA OSCs.

https://doi.org/10.1002/aenm.202103940.