This technology involves cooling a precursor solution of P3HT dissolved in chloroform to -10°C for a brief aging period, followed by direct spin-coating. This allows molecular alignment to be completed in the solution phase before the thin film is formed. The resulting thin film is then used as the semiconductor layer in field-effect transistors.
Spin-coating typically results in nearly amorphous thin films because the solvent evaporates too quickly for an ordered structure to develop. To compensate, additional post-processing steps like thermal or solvent annealing are required, which complicates the process and reduces efficiency.
By leveraging the temperature-dependent solubility of P3HT, this technology enables the chains within the solution to self-assemble into crystals at low temperatures. This allows for the creation of a highly crystalline thin film in a single coating step, eliminating the need for post-processing. Even with a thin film of 25–31 nm, an average field-effect mobility of 4.0×10^-2 cm2/Vs is achieved. This can be applied to large-area mass production of printed organic electronic devices, reducing process steps while increasing mobility by over an order of magnitude.
This invention was developed with support from the Ministry of Science, ICT and Future Planning for the development of high-performance organic electronic devices using the self-assembly of π-electron molecules.
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