Effective mobility in amorphous organic transistors: Influence of the width of the density of states

• High mobility P3HT/PS OTFTs have been fabricated and measured between 130 and 350 K.
• The mobility dependence on gate bias is found to be very sensitive to temperature.
• An advanced numerical OTFT model was used to simulate the I–V characteristics.
• Good agreement was obtained over the whole range with a unique parameter set.
• The P3HT/PS (1:5) Gaussian DOS width was found close to 45 meV.

The temperature dependence of poly(3-hexylthiophene-2,5-diyl) (P3HT)/polystyrene (PS) blend organic transistor current/voltage (I–V) characteristics has been experimentally and theoretically studied. The planar transistors, realized by drop casting the P3HT/PS ink, exhibit high mobilities (over 5 × 10−3 cm2 V−1 s−1) and good overall characteristics. A transistor model accounting for transport mechanisms in disordered organic materials was used to fit the measured characteristics. Using a single set of parameters, the measured effective mobility versus gate bias, either increasing or decreasing with the gate bias depending on temperature, is well reproduced over a wide temperature range (130–343 K). A Gaussian density of states width of 0.045 eV was determined for this P3HT/PS blend. The transistor I–V characteristics are very well described considering disordered material properties within a self-consistent transistor model.

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