Jing's work is accepted in JACS

A range of alkoxythiophene additives with varied alkyl chain length are designed to tune the geometry of state-of-the-art polymer donor PM6 and D18 fibrils. These additives preferentially entangle with the alkyl side chains of polymer donors and regulate their lamellar stackingthat eventually leads to varied fibril diameter. With the fibril diameter, up to ca. 28 nm, the exciton dissociation and charge transport processes become more efficient, leading to a maximum PCE over 20% in D18/L8-BO binary solar cells.