Fully printed organic thin film transistors (OTFT) based flexible humidity sensors

Abstract

A flexible fully printed organic thin film transistor (OTFT) was successfully fabricated and employed as a humidity sensor. The bottom gated OTFT, with width to length ratio (w/l) ratio of 26, was printed on a flexible poly ethylene terephthalate (PET) substrate. Conductive gate and dielectric layers were printed using gravure printing technique. Source and drain electrodes were deposited by means of screen printing. An active layer of pentacene, a humidity sensitive material, was deposited using inkjet printing. The current-voltage characteristics of the fully printed device were studied from 25% RH to 90% RH. A percentage change of 2000 % at 90% RH, in the drain current (I D ), was registered when compared to the I D at 25% RH. The response of the fully printed sensor towards relative humidity was studied and is reported in this paper.