Temperature Dependence of Sensing Characteristics for OTFT-Based Hydrogen Sensor

Abstract

An organic thin-film transistor (OTFT)-based hydrogen sensor with palladium (Pd) source/drain (S/D) electrodes as the sensing medium is fabricated, and the effects of operating temperature on its sensing performance are investigated. The sensor exhibits a current decrease upon exposure to hydrogen, and a rapid and reversible H2 response upon the introduction and removal of hydrogen is observed. Heating the sensor changes its electrical characteristics and thus its hydrogen sensitivity. It is found that the effects of temperature on the hydrogen solubility and sticking coefficient of the Pd electrodes are important factors determining the sensitivity at a high temperature of 90 °C, but the temperature dependences of carrier mobility and threshold voltage of the OTFT become dominant at lower temperatures of 60 °C and 30 °C. Moreover, shorter response time is realized at higher operating temperature because higher temperature accelerates the diffusion of H atoms in the Pd electrode. However, the recovery time does not show the same trend due to a reconstruction of the pentacene layer at high operating temperature.