Enabling high-performance, centimeter-scale organic solar cells through three-dimensional charge transport

Organic solar cells (OSCs) suffer from severe upscaling loss due to the inevitable formation of inhomogeneities and the intrinsically low charge mobilities of organic materials limiting the charge extraction efficiency, especially in the situation where cell width reaches centimeter scale. Here, we report the introduction of a nematic liquid crystal donor, BTR-Cl, into a typical non-fullerene blending system of PM6:BTP-eC9. The participation of BTR-Cl contributes to a significantly improved crystallinity and ordering of the host components and facilitates efficient three-dimensional charge transport in the active layer. Simultaneously improved fill factor and current density are thus achieved in BTR-Cl-doped OSCs, corresponding to a superior efficiency of 18.31%. More importantly, a high efficiency of 16.88% along with a robust fill factor of 73.4% is retained when enlarging the effective device area from 0.034 to 1.01 cm², highlighting the importance of three-dimensional charge transport in reducing the upscaling loss of OSCs.