Structural Alternation Correlated to the Conductivity Enhancement of PEDOT:PSS Films by Secondary Doping

TL;DR

This study investigates how secondary doping with ethylene glycol induces nanoscale structural changes in PEDOT:PSS films, leading to increased conductivity through nano-crystallization of PEDOT molecules.

Contribution

It reveals the nanoscale structural mechanism, specifically nano-crystallization, underlying conductivity enhancement in PEDOT:PSS films due to secondary doping.

Findings

Nano-crystallization of PEDOT molecules occurs near critical doping levels.

Structural uncoupling of PEDOT from PSS correlates with conductivity increase.

Secondary doping induces nanoscale structural changes critical for performance.

Abstract

"Secondary doping" in poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) is quite effective and a frequently used method for the conductivity enhancement. This simple approach, the addition of co-solvents to the PEDOT:PSS solution before film fabrication, is an essential way to derive the high electrical performance of PEDOT:PSS, but the mechanism still remains unclear. In this study, nanoscale structural changes synchronized with the conductivity enhancement via secondary doping in PEDOT:PSS films were investigated. During secondary doping with ethylene glycol near the critical dopant concentration, non-crystalized PEDOT molecules uncoupled from PSS chains and then underwent nano-crystallization. These structural changes might be the key driving force for conductivity enhancement via secondary doping.