posted on 2021-04-08, 11:34authored byGang Ye, Jian Liu, Xinkai Qiu, Sebastian Stäter, Li Qiu, Yuru Liu, Xuwen Yang, Richard Hildner, L. Jan Anton Koster, Ryan C. Chiechi
We demonstrate the
impact of the type and position of pendant groups
on the n-doping of low-band gap donor–acceptor (D–A)
copolymers. Polar glycol ether groups simultaneously increase the
electron affinities of D–A copolymers and improve the host/dopant
miscibility compared to nonpolar alkyl groups, improving the doping
efficiency by a factor of over 40. The bulk mobility of the doped
films increases with the fraction of polar groups, leading to a best
conductivity of 0.08 S cm–1 and power factor (PF)
of 0.24 μW m–1 K–2 in the
doped copolymer with the polar pendant groups on both the D and A
moieties. We used spatially resolved absorption spectroscopy to relate
commensurate morphological changes to the dispersion of dopants and
to the relative local doping efficiency, demonstrating a direct relationship
between the morphology of the polymer phase, the solvation of the
molecular dopant, and the electrical properties of doped films. Our
work offers fundamental new insights into the influence of the physical
properties of pendant chains on the molecular doping process, which
should be generalizable to any molecularly doped polymer films.