Low-voltage Operation Solution-processed Thin Film Transistors with Various Dielectrics

This paper investigates the effect of gate dielectric structures on the low-voltage operation of solution-processed Diketopyrrolopyrrole-thienothiophene copolymer (DPP-DTT) organic thin-film transistors. Devices were fabricated using 300 nm SiO₂, 100 nm SiO₂, and 32 nm Al₂O₃ gate dielectrics. ODTS and ODPA self-assembled monolayers were introduced on the SiO₂ and Al₂O₃ surfaces, respectively, to improve the semiconductor/dielectric interface. The device with 300 nm SiO₂ operated at 100 V, showing an on/off current ratio of 1.93 × 10⁵ and a mobility of 0.54 cm² V⁻¹ s⁻¹. Reducing the SiO₂ thickness to 100 nm lowered the operating voltage to 50 V and increased the mobility to 1.4 cm² V⁻¹ s⁻¹. Notably, the 32 nm Al₂O₃-based device operated at only 5 V with an on/off ratio of 1.86 × 10⁴. These results demonstrate that gate dielectric engineering is effective for low-power organic thin-film transistors.