N‑type Self-Doping of Fluorinate Conjugated Polyelectrolytes for Polymer Solar Cells: Modulation of Dipole, Morphology, and Conductivity

For the conjugated polyelectrolytes (CPEs) interlayers, many studies focus on the modulation of interfacial dipoles in the polymer solar cells (PSCs) by altering the side polar groups but usually ignore the functions of conjugated backbone engineering (CBE) through the delicate design to improve their functions. Herein, novel alcohol-soluble CPEs by incorporation of fluorinate benzene onto the backbone, namely PFf1B and PFf4B, have been synthesized to modulate the interfacial dipoles and charge mobility. A favorable bidipole composed of ion-induced dipole and F hydrogen bond-induced dipole was discovered to be responsible for the tunable work function of indium tin oxide (ITO) electrode. Moreover, a desirable nanowires morphology of the upper active layer has also been obtained with the help of the self-assembly of fluorinated CPEs. More intriguingly, an unusual n-type doping favored by fluorine-induced electron transfer (FIET) was observed in these CPEs, leading to the improvement in the electron mobility. As a consequence, these fluorinated CPEs were demonstrated with a general application in the PSCs based on various active layers. Note that PFf4B with the highest loading of F atoms can work efficiently in a thickness of up to 31.8 nm, which broke the thickness limitation of most reported CPEs interlayer.