Charge Transport Dynamics in Doped Organic Polymer: Effect of New Split‐Functional Dopant on an Amorphous Organic Semiconductor

ABSTRACT

Understanding the microscopic mechanisms governing charge transport in electronically doped conjugated polymers is important from both fundamental and device perspectives. Here, we investigate an amorphous semiconducting polymer, PTB7‐Th, as a suitable host to incorporate a specific organic salt system. The electronically disordered polymer, when doped with a split functional dopant that consists of organic cation 4‐(acetylamino)‐2,2,6,6‐tetramethyl‐1‐oxo‐piperidinium (ATOP) and the bulky anion tetrakis[3,5‐bis(trifluoromethyl)phenyl] borate (BARF), undergoes a major enhancement in electrical transport. In addition to enhancing solubility, the BARF counterion effectively minimizes the coulombic interaction between the anion and the charge carrier on the polymer backbone, which facilitates efficient ion‐pair dissociation. A six‐order‐of‐magnitude enhancement in conductivity and a significant improvement in carrier mobility are observed in optimally doped samples. Temperature‐dependent DC conductivity measurements indicate variable‐range hopping transport, with improved hopping parameters upon doping. Additionally, AC measurements reveal faster carrier relaxation, systematic activation energy changes, and minimal ionic migration, highlighting improved electronic transport upon doping. Complementary molecular dynamics simulations capture ion–polaron and ion–ion correlations that rationalize the observed transport enhancement. The results highlight the connection from microscopic interactions to macroscopic enhancement in electrical performances while also identifying the origin of saturation beyond a critical dopant concentration.