Flexoelectric Response of PEDOT:PSS Films at Different PSS Contents

Faced with the growing global energy demand, the search for alternative and sustainable solutions is increasing. This quest for new technologies requires an in-depth investigation of material properties, particularly the study of multiphysics couplings that are still under intense investigation. Flexoelectricity, defined as the coupling between a mechanical strain gradient and electrical polarization in dielectrics and semiconductors, is of particular interest due to its potential for mechanical-to-electrical energy conversion. To date, few studies have investigated the flexoelectric response of polymers. This article aims to address this gap by examining the influence of the PSS to PEDOT ratio in the semiconducting PEDOT:PSS blend on its dielectric and flexoelectric properties. To this end, we fabricated devices with a trilayer cantilever structure (top electrode/polymer/bottom electrode) and analyzed the impact of various PSS to PEDOT mass ratios (ranging from 2.5, 6 and 20) on the thermal, morphological, mechanical and dielectric properties of the material. Additionally, we studied the effect of incorporating a small fraction of xylitol as a secondary dopant into the PEDOT:PSS blend. This addition significantly enhanced the flexoelectric coefficient of PEDOT:PSS (1:2.5) from 1.3 to 11 μC/m. Regarding flexoelectric energy conversion efficiency, which depends on the dielectric, mechanical and flexoelectric properties, the PEDOT:PSS (1:6) composition offered the best compromise. Finally, we examined the influence of postrinsing treatment of the polymer film with ethanol and methanol on the flexoelectric coefficient. This treatment, combined with the addition of xylitol, led to a large improvement in the flexoelectric coefficient of PEDOT:PSS (1:6) from 6.21 to 11.41 μC/m.