Solution-processed organic micro crystal transistor based on tetraceno[2,3-b]thiophene from a monoketone precursor

Abstract

The synthesis, thermal and photophysical properties, and solution-processed organic field effect transistors fabricated from a soluble tetraceno[2,3-b]thiophene precursor 1. Compound 1 was synthesised in 9.8% through 6 steps. The TGA profiles showed that a 9.1% weight loss occurred at ca. 130 °C, corresponding to an expulsion of a carbonyl group. The photogeneration of tetraceno[2,3-b]thiophene from 1 in the solution state could be fitted into a first-order rate law with a rate constant (k) of 2.05 × 10⁻²s⁻¹ in a yield of 55.6% (±0.9%) under a 1.25 mW cm⁻² UV lamp. The platelet micro crystals of 1, formed either by heat or by light, were confirmed by XRD to be identical to a simulated one from reported X-ray crystallographic data. The field effect mobility across a single crystal was measured to be 4.75 × 10⁻¹ cm² V⁻¹s⁻¹ with on/off ratio 10⁵. The high purity of single crystals formed both by heat and by light are supported by an EPR analysis. This is the first report of a solution-processed single-crystal OFET of linear acenes without bulky substituent groups. In another experiment, the devices made directly from an amorphous thin film of 1, prepared by spin-coating, exhibited a charge mobility 3.0 × 10⁻⁴ cm² V⁻¹s⁻¹ with on/off ratio 10³.