Análise da dopagem em transistores eletroquímicos orgânicos

Abstract

Organic Electrochemical Transistors (OECTs) have emerged as essential platforms in bioelectronics due to their ion to electron transduction capability via volumetric coupling. However, while significant effort has been dedicated to polymer synthesis, the influence of the electrolyte chemical nature on the doping mechanism remains under explored. This dissertation investigates how the physicochemical properties of anions specifically hydration energy and hydrodynamic radius govern the operating efficiency of poly(3-hexylthiophene) (P3HT)-based OECTs. Devices were fabricated and characterized using five distinct electrolytes (NaCl, NaClO2, NaClO3, NaClO4, and Na2SO4), selected to cover different positions within the Hofmeister Series. Electrical characterization revealed a critical dependence of performance on anion desolvation: the device using NaClO4 (a chaotropic, weakly hydrated anion) exhibited superior performance, with an effective volumetric mobility (𝜇𝐶*) of ≈ 130 F · cm−1V−1s−1 and an 𝐼𝑂𝑁/𝐼𝑂𝐹 𝐹 ratio of 106. In contrast, NaCl (a kosmotropic, strongly hydrated anion) limited the device to low-efficiency surface behavior (𝜇𝐶* ≈ 0.14), with injection barriers evidenced by non-linear contacts. In situ UV-Vis absorption spectroscopy corroborated these findings, demonstrating that the density of polarons formed within the polymer is governed by the anion ability to penetrate the hydrophobic matrix. Therefore electrolyte selection is not trivial but a powerful engineering tool to tune the transition between surface and volumetric operation regimes, validating the Hofmeister Series as a predictive model for optimizing bioelectronic devices.