Extraction of the sub-bandgap density-of-states in polymer thin-film transistors with the multi-frequency capacitance-voltage spectroscopy

Abstract

The multi-frequency capacitance-voltage (C-V) spectroscopy is proposed for extracting the sub-bandgap density-of-states (DOS) of polymer semiconductors and demonstrated in three different thiophene-based organic thin-film transistors including poly(3-hexylthiophene), poly(3,3′′′-didodecylquaterthiophene), and poly(didodecylquaterthiophene-alt-didodecylbithiazole). The density of exponential tail and exponential deep states are extracted to be in the range of 3.0 × 1018 ∼ 1.5 × 1019 cm−3 eV−1 and 3.0 × 1016 ∼ 3.0 × 1017 cm−3 eV−1, respectively. The extracted DOS correspond to the polymer semiconductor-dependence of the measured crystallinity and mobility. In addition, the extracted DOS values are verified by comparing the measured I-V characteristics with the simulated results through a technology computer-aided design tool.