Piezopotential Gated Self-Biased Conducting Polymer-Based Flexible Transistor for Mechanical Energy Harvesting Device

Abstract

A self-biased thin-film transistor (TFT) has been fabricated by using poly(3, 4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) as a conducting channel that works as an efficient mechanical energy harvesting device. The self-biasing of this top-gated TFT has been accomplished through the integration of two voltage sources within the device structure, which are essential for its operation. The LiF/Al and MoO3/Ag electrodes serve as the source and drain, respectively, of this TFT that has a work-function difference of ∼−1.16 eV, which works as the drain bias (VD). The poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) thin film that has been employed as a gate dielectric generates a piezo-potential due to the application of external pressure and works as gate bias (VG) of this TFT. The unique feature of this device is its prolonged electrical power generation in DC form during the application of mechanical force that enables us to measure its mechanical-to-electrical power conversion energy accurately. The extracted power conversion efficiencies of hard and flexible (flat) substrate-based TFTs are 0.4 and 1.9%, respectively. Interestingly, the conversion efficiency of a flexible TFT increases with bending and can reach up to 33% which is unusually high for a mechanical energy harvesting device. In addition, electrical characterization of these devices shows transistor-like behavior with an On-Off ratio and subthreshold swing of 2 × 102 and 5.88 N/decade, respectively, for hard substrate, while on a flexible substrate, these values are 1 × 104 and 1.35 N/decade, respectively. © 2025 American Chemical Society.