"Understanding the Impact of Oligomeric Polystyrene Side Chain Arrangement on the All-Polymer Solar Cell Performance"

Tadanori Kurosawa: Xiaodan Gu, Kevin L. Gu, Yan Zhou, Hongping Yan, Cheng Wang, Ging-Ji Nathan Wang, Michael F. Toney, and Zhenan Bao; Advanced Energy Materials, 09/14/17.

Additional Authors: Xiaodan Gu, Kevin L. Gu, Yan Zhou, Hongping Yan, Cheng Wang, Ging-Ji Nathan Wang, Michael F. Toney, and Zhenan Bao

Abstract:

The introduction of oligomeric polystyrene (PS) side chains into the con-
jugated backbone is proven to enhance the processability and electronic prop-
erties of semiconducting polymers. Here, two series of donor and acceptor
polymers are prepared with different molar percentages of PS side chains
to elucidate the effect of their substitution arrangement on the all-polymer
solar cell performance. The observed device performance is lower when the
PS side chains are substituted on the donor polymer and higher when on the
acceptor polymer, indicating a clear arrangement effect of the PS side chain.
The incorporation of PS side chains to the acceptor polymer contributes to
the decrease in phase separation domain size in the blend films. However,
the reduced domain size was still an order of magnitude larger than the
typical exciton diffusion length. A detailed morphological study together with
the estimation of solubility parameter of the pristine PS, donor, and acceptor
polymers reveals that the relative value of solubility parameter of each com-
ponent dominantly contributes to the purity of the phase separated domain,
which strongly impacts the amount of generated photocurrent and overall
solar cell performance. This study provides an understanding of the design
strategies to improve the all-polymer solar cells.