Probing n-Type Conduction in Eumelanin Using Organic Electrochemical Transistors

Sustainability demands innovative materials and technologies to address environmental and societal needs. In this context, natural biomaterials are gaining significant attention, with eumelanin (EuM) standing out due to its biocompatibility, abundance, and distinct electronic properties. However, the conducting nature of EuM and the main carrier involved in the charge transport have been the subject of a long-standing and inconclusive debate. This work contributes to this discussion by presenting the observation of n-type conduction in EuM films employed as channel material in organic electrochemical transistors (OECTs). The device current is modulated based on strong ionic electronic coupling between electrolyte cations and the π electron system of EuM’s indole units, resulting in charge mobility of μOECT = 0.019 ± 0.016 cm2 V–1 s–1. Our findings provide an innovative contribution to the ongoing debate on the semiconducting properties of EuM and demonstrate a novel electronic device, highlighting the remarkable potential of EuM for sustainable electronics.