Low Temperature Processed Organic Tfts with Solution-Processable Al2O3 Gate Insulator Using Hydrogen Peroxide

Abstract

Organic semiconductors are considered as a replacement for amorphous silicon in thin-film transistor (TFT) applications, since they have shown comparable electrical properties and potential advantages for their compatibility with plastic substrates. However, the high operating voltages of these TFTs still need to be reduced for any practical application. Among dielectric materials, aluminum oxide (Al2O3) appears to be promising due to its high dielectric constant, its robustness and its possibility to be prepared on different type of substrates under easy process. However, high quality and high dielectric constant films generally require annealing temperature above 400 oC, which is not suitable for high-throughput and flexible electronic devices. In this study, we fabricated the bottom-gate and top-contact organic TFTs on glass substrate. Al gate electrode was deposited by thermal evaporation while Al2O3 thin films, used as gate insulators, were grown by spin coating. Employing hydrogen peroxide (H2O2) in the solution process helps reduce defects at the interface between channel and G/I through strong oxidation and minimize organic chemical-induced defects, such as pores, pin holes, and organic residues, through decomposing organic chemicals at low temperature. The growth of the Al2O3 thin films with H2O2 was studied with various annealing temperatures from 100 ~ 300 oC and solution concentration of 0.1 ~ 1 M. Pentacene was evaporated through shadow mask at a rate of 0.3 Å/s to form a 70 nm thick active layer. Gold source/drain (S/D) electrodes (100 nm) were patterned using shadow mask on the pentacene layer. The performance of the solution processed Al2O3 based TFT was validated using capacitance-voltage and current-voltage analysis.