Boosting charge separation in organic photovoltaics: unveiling dipole moment variations in excited non-fullerene acceptor layers
Akira Yamakata, Kosaku Kato, Takumi Urakami, Sota Tsujimura, Kasumi Murayama, Masahiro Higashi, Hirofumi Sato, Yasuhiro Kobori, Tomokazu Umeyama, Hiroshi Imahori
Abstract
, V-type molecular stacking) induce instantaneous intermolecular CT and CD in the neat ITIC layer. In contrast, J-type stacking does not support such CT and CD. This previously unknown pathway is triggered by the larger dipole moment change on the excited state generated at the lower symmetric V-type molecular stacking of ITIC. This is in sharp contrast with the need of sufficient energy offset for CT and CD at the donor-acceptor heterojunction, leading to the significant voltage loss in conventional OPVs. These results demonstrate that the rational molecular design of NFAs can increase the local dipole moment change on the excited state within the NFA layer. This finding paves the way for a groundbreaking route toward the commercialization of OPVs.