High-Performance Solution-Processed Low-Voltage Polymer Thin-Film Transistors With Low-<inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula>/High-<inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> Bilayer Gate Dielectric

Abstract

Solution-processed low-voltage organic thin-film transistors (OTFTs) were fabricated using the high-mobility donor–acceptor copolymer semiconductor indacenodithiophene-co-benzothiadiazole (IDTBT) and large permittivity (high- $k$ ) relaxor ferroelectric polymer poly (vinylidene fluoride-trifluoroethylene-chlorofloroethylene). It is shown that, with the face-on molecule packing in as-deposited IDTBT films, the close interfacing between the backbone and the dielectric layer causes significant mobility degradation of the fabricated OTFTs due to dipole effects. By inserting a thin, low-polar dielectric layer between the high- $k$ one and the channel, the dipole field can be effectively screened and the devices present a high mobility similar to that of previously reported high-voltage IDTBT OTFTs. With the bilayer gate dielectric and the IDTBT semiconductor, low-voltage OTFTs are achieved with the average mobility of 1.4 cm $^{\mathrm {\mathbf {2}}}/\text{V}\,\cdot $ s and ON/OFF-current ratio larger than $10^{6}$ , which is among the best reported performance so far for solution processed low-voltage OTFTs.