Threshold voltage tuning in gelatin biopolymer-gated high-performance organic field-effect transistors

Natural biopolymers have been of considerable interest in developing flexible, biocompatible and biodegradable organic electronic devices. Herein, we demonstrate gelatin biopolymer gated OFETs utilizing thermally evaporated α-sexithiophene (α-6T) and solution-processable poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C14) as organic semiconductors (OS). The tunability of threshold voltage (VT) for the OFETs as a function of lithium-perchlorate (LP) content (% w/w) in gelatin is also explored. With the increase of LP (0% to 20% w/w) in the gelatin, VT reduces from − 5.7 V to − 1.75 V and − 2.15 V to + 0.1 V for α-6T and PBTTT-C14 based OFETs, respectively. The highest hole mobility in the saturation regime (μS) of α-6T and PBTTT-C14 is estimated as 2.0 cm2V−1s−1 and 0.1 cm2V−1s−1 respectively with the on/off ratio ∼103. It is ascribed to the efficient formation of an electric double layer (EDL) at the dielectric/organic interface. The reduction in the VT upon LP incorporation can be attributed to the additional ionic contribution of ClO4- to the EDL along with the trap density (NT) reduction at dielectric/OS interface. [Display omitted] •High mobility of 2 cm2V−1s−1 for biopolymer-gated organic field-effect transistors.•Low threshold of ≈ 0.1 V realized for flexible and solution-processable transistors.•Threshold voltage tuned while maintaining high mobility upon addition of lithium salt.