Performance of organic thin-film transistors

An investigation of the performance of organic and polymeric thin-film transistors (OTFTs) made of several organic semiconducting and insulating materials in the last two decades is presented, in an attempt to capture the state-of-the-art experimental values for effective mobility, threshold voltage, on/off ratio, and subthreshold slope in OTFTs made of different materials by different fabrication approaches. The analysis of published data demonstrates that the effective mobility decreases when the product of the semiconducting film thickness (tO) and gate capacitance per unit area (CI) increases. The decrease is given by a power-law function with parameters for several organic semiconductors, and examples are provided on how the deduced trend can be used in the practical design of organic circuits. The second observation is that the polarity of the OTFTs’ threshold voltage VT is random, but the spread in magnitudes of ∣VT∣ decreases, when CI increases. This trend, together with the third observation that the subthreshold slope tends to decrease when CI increases, is weak and no strong correlation between subthreshold slope and on/off ratio in the published data was found.