OFET Sensors with Poly 3-hexylthiophene and Pentacene as Channel Materials for Ionizing Radiation

Abstract

Pentacene and poly 3-hexylthiophene (P3HT) are the most promising p-type organic semiconducting materials for fabrication of organic field effect transistors (OFETs). OFETs with aforesaid organic semiconducting materials have been demonstrated as total dose detectors for ionizing radiation, wherein the changes in the electrical characteristic parameters, such as, increase in the OFF current, increase in the ON current, change in the current ratio, shift in the threshold voltage, change in the subthreshold swing, etc., were used as a measure of ionizing radiation dose. Upon exposure to ionizing radiation P3HT based OFET sensor has shown an OFF current sensitivity of 4.4 nA/Gy while pentacene based OFET sensor has shown an OFF current sensitivity of 26.7 nA/Gy for a total of 50 Gy dose of ionizing radiation. Change in the conductivity of the thin-films of pentacene and P3HT were observed and compared using electrostatic force microscopy (EFM) imaging before and after exposure to ionizing radiation. Effects of ionizing radiation on the energy band structures of the organic semiconducting materials, pentacene and P3HT, have been studied using UV-visible spectroscopy. Moreover, analysis of UV-visible spectra of the thin-films suggested the generation of energy states in larger quantity in case of pentacene thin-film as compared to P3HT thin-film upon exposure to the same dose of ionizing radiation. These results confirm the higher sensitivity observed in pentacene OFET sensor as compared to P3HT OFET sensor in terms of the change in electrical parameters.

A Thermoelectric Polymer Field-Effect Transistor via Iodine-Doped P3HT

“…Polymers appear very attractive as active layers in OFETs due to inherent advantages such as low cost [1,2] and being lightweight [3,4], flexible, [5,6], biocompatible [7], scalable [8,9], and processable at relatively low temperatures [10]. They have also been demonstrated as the active layer for a variety of applications including sensors [11,12] and displays [13,14]. Yet, when compared to other classic semiconductor devices, polymer devices are plagued by low mobility, low output current, and a small on/off ratio.…”

A Thermoelectric Polymer Field-effect Transistor via Iodine-doped P3HT

“…They have demonstrated a propensity for being low cost 1,2 , lightweight 3,4 , flexible, 5,6 , biocompatible 7 , scalable 8,9 , and processable at low temperatures. 10 They have also been demonstrated as the active layer for a variety of applications including sensors 11,12 and displays. 13,14 Yet, when compared to other organics such as evaporated small molecule active layers, polymer devices are plagued by low mobility, output current, and onoff ratios.…”