Single‐Solution Doping Enabling Dominant Integer Charge Transfer for Synergistically Improved Carrier Concentration and Mobility in Donor–Acceptor Polymers

Abstract

AbstractChemical doping of donor–acceptor (D–A) polymers is essential for their usage in highly efficient optoelectronic devices. The crucial challenge remains to synergistically improve the carrier concentration and mobility of these polymers via a single solution doping method. Here, a D–A polymer, Pg32T‐OTz is designed and synthesized, containing a weak‐acceptor–strong‐donor backbone with nonpolar (alkoxy) and polar (ethylene glycol) side chains. Pure integer charge transfer (ICT) is shown to occur in 2,3,5,6‐tetrafluoro‐tetracyanoquinodimethane (F4TCNQ)‐doped D–A polymer at a low doping level. It is shown that the ordered edge‐on orientations of ICT structures overcome the Coulomb interactions and endow a long‐range hole delocalization, while few charge transfer complex states form in amorphous regions and bridge the crystalline ICT structures at high doping level, creating a network that sustains efficient charge transport. As a result, simultaneously high carrier concentration and high mobility are realized for F4TCNQ‐doped Pg32T‐OTz and thus a high electrical conductivity up to 550 S cm−1 is approached, which is the highest value among any doped polymers via a single‐solution doping process. This work demonstrates that the modulation of the acceptor strength combined with side‐chain engineering is an effective molecular design strategy to promote both the doping efficiency and carrier transport property of D–A polymers.