Charge-Transfer Intermediates in the Electrochemical Doping Mechanism of Conjugated Polymers

Abstract

We address the nature of electrochemically induced charged states in conjugated polymers, their evolution as a function of electrochemical potential, and their coupling to their local environment by means of transient absorption and Raman spectroscopies synergistically performed in situ throughout the electrochemical doping process. In particular, we investigate the fundamental mechanism of electrochemical doping in an oligoether-functionalized 3,4propylenedioxythiophene (ProDOT) copolymer. The changes embedded in both linear and transient absorption features allow us to identify a precursor electronic state with charge-transfer (CT) character that precedes polaron formation and bulk electronic conductivity. This state is shown to contribute to the ultrafast quenching of both neutral molecular excitations and polarons. Raman spectra relate the electronic transition of this precursor state predominantly to the C β -C β stretching mode of the thiophene heterocycle. We characterize the coupling of the CT-like state with primary excitons and electrochemically induced charge-separated states, providing insight into the energetic landscape of a heterogeneous polymer-electrolyte system and demonstrating how such coupling depends on environmental parameters, such as polymer structure, electrolyte composition, and environmental polarity.

Enhancing the Ionic Conductivity of Poly(3,4-propylenedioxythiophenes) with Oligoether Side Chains for Use as Conductive Cathode Binders in Lithium-Ion Batteries

“…Electrochemical doping of conjugated polymers generates polarons and bipolarons, the movement of which along or between the polymer chains invariably results in enhanced electronic conductivity. − Hence, the charge-transport properties in these systems are a function of degree of doping. The electronic conductivity further depends on the charge carrier density and mobility, which is again dependent on the degree of doping.…”

Influence of Molecular Weight on the Organic Electrochemical Transistor Performance of Ladder‐Type Conjugated Polymers

“…[ 1 ] In OMIECs, the strong coupling between ions and electrons enables efficient charge storage and signal transduction. [ 2 ] For this reason, OMIECs have found applications in electrochromic displays, [ 3 ] light‐emitting electrochemical cells, [ 4 ] supercapacitors/batteries, [ 5 ] sensors, [ 6 ] thermoelectrics, [ 7 ] and actuators, [ 8 ] to name just a few. When implemented as the active channel materials in organic electrochemical transistors (OECTs), [ 9 ] OMIECs endow these devices with record‐high transconductance, low operational voltage, and high current density.…”

Water-Induced Tuning of the Emission of Polyaniline LEDs within the NIR to Vis Range

“…The diode formed with dry polyaniline doped with p -toluenesulfonic acid (solid pressed pellet, with a thickness of 0.5 ± 0.01 mm and a diameter of 3 mm) emits mostly in NIR with a maximum at 840–885 nm (Figures and a). This corresponds to the excitations of π-electrons and emission due to the charge-transfer (CT) processes in organic materials. ,− Here, CT between PTSA and polyaniline and also between quinoid and aromatic moieties in polyaniline chains is to be considered, including the formation of polarons that are weakly emissive…”