High performance all-polymer solar cells employing systematically tailored donor polymers

•High performance (PCE = 5.35%) achieved for all-PSCs through introduction of electron-withdrawing fluorine atoms to polymer acceptor unit and change the alkyl side chain in polymer donor unit.•Systematical modifications on the chemical structure of the donor polymers in all-PSCs.•Investigation of introduction of electron-withdrawing fluorine atoms to polymer acceptor unit effect on optical property, polymer coplanarity, intermolecular packing and balanced carrier transport.•Investigation of change alkyl side chain in polymer donor unit effect on film morphology and hole transport.

We successfully designed and synthesized a series of BDT-Qx-T based polymers as the donor polymer used in all polymer solar cells (all-PSCs). Their properties were finely tuned by side-chain modification and the introduction of electron-withdrawing fluorine atoms to polymer acceptor unit. Then we systematically investigated the effect of molecular structure on the polymer morphology and photovoltaic properties in all-PSCs. We revealed that the fluorination can optimize polymer energy level and improve the polymer coplanarity, leading to enhanced intermolecular packing and balanced carrier transport. Meanwhile, the substitution of dodecyl for 2-ethylhexyl side chains can result in improved film morphology and hole transport. As a result of the synergistic effect between fluorination and side-chain modification, we achieved a high PCE of 5.35% for the optimized all-PSCs. More importantly, our approach may become a general and effective way to tailor the polymer molecular structure for achieving high performance all-PSCs.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide