Tuning Properties of Conjugated Polyelectrolytes for Opto-Electronic Devices

Conjugated polyelectrolytes (CPEs) are materials that comprise a conjugated polymer backbone with pendant ionic groups and counter ions. Their pendant ionic side chains make CPEs soluble in polar solvents including water, methanol, dimethylformamide, and dimethylsulfoxide, which presents the opportunity to move away from environmentally unfriendly halogenated solvents toward more green, sustainable solvents. CPEs have been used in sensing of small ions as well as biomolecules, proteins, and DNA, as interfacial interlayers in OLEDs, organic photovoltaics (OPVs), perovskite solar cells, organic photodetectors, and OFETs, and as active layers in OLEDs, polymer light-emitting electrochemical cells (PLECs), OPVs, dye sensitized solar cells (DSSCs), thermoelectrics, pseudocapacitors, and organic electrochemical transistors (OECTs). Among reported CPEs, some can be doped in the presence of a proton source, and thus, have a neutral pH ~ 7. This doping process has been referred to as “self-dope” in the literature because a proton source comes from a solvent used to dissolve the CPE as opposed to the traditional doping method by adding a dopant molecule. These self-doped CPEs can be used as a conductive buffer layer in OLEDs, OPVs, and organic photodetectors (OPDs) to replace poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). In this talk, I will discuss the development of CPEs and how chemical structures and processing protocols can be used to tune the optical, electronic, and ionic charge transport, mechanical property and therefore device performance such as OECTs and OPDs.