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 alpha-sexithiophene (alpha-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 (V-T) 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, V-T reduces from - 5.7 V to - 1.75 V and - 2.15 V to + 0.1 V for alpha-6T and PBTTT-C14 based OFETs, respectively. The highest hole mobility in the saturation regime (mu(S)) of alpha-6T and PBTTT-C14 is estimated as 2.0 cm(2)V(- 1)s(-1) and 0.1 cm(2)V(- 1)s(-1) respectively with the on/off ratio similar to 10(3). It is ascribed to the efficient formation of an electric double layer (EDL) at the dielectric/organic interface. The reduction in the V-T upon LP incorporation can be attributed to the additional ionic contribution of ClO4- to the EDL along with the trap density (N-T) reduction at dielectric/OS interface.