Directly extracting the density of trap states in electrolyte-gated thin-film transistors

We derive a method for extracting the trap density of states (DOS) in electrolyte-gated thin-film transistors (EG-TFTs) using only transfer measurements. We follow the approach of a well-established scheme for extracting the DOS in thin-film transistors [M. Grünewald et al., Phys. Stat. Sol. B 100, K139 (1980)], combined with the Gouy-Chapman model for electrical double layers. We apply the method to the transfer characteristics of a poly(3-hexylthiophene)-based EG-TFT with water as the electrolyte. The extracted DOS is consistent with results from prior studies on low-voltage organic thin-film transistors, demonstrating the method's validity and potential for broader application.