Tuning Molecular Interaction in Polymer Solar Cells via a Multifunctional Discotic Component to Enhance Photovoltaic Response

Abstract

A donor–acceptor (D–A)‐type discotic organic material (TP‐2‐PIE), having a self‐organization ability, is selected to be the third component blending with poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b’]dithiophene‐co‐3‐fluorothieno [3,4‐b]‐thiophene‐2‐carboxylate] (PTB7‐Th): [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) in ternary bulk‐heterojunction polymer solar cells. The complementary absorption and energy transfer between TP‐2‐PIE and PTB7‐Th contributes to the enhancement in photocurrent generation, improving the short‐circuit current. In addition, TP‐2‐PIE alters the molecular interaction leading to an enhanced phase separation, which promotes carrier transport with a good balance and minimizes the density of trap states simultaneously. In this way, the overall photovoltaic performances are markedly enhanced at an optimal condition of 10 wt% TP‐2‐PIE in donors with a 12.6% efficiency increase. Current understanding on the functionality of this third component in ternary solar cells may be able to guide future device development.