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Sensors 2014, 14(9), 16287-16295;

Achieving a Good Life Time in a Vertical-Organic-Diode Gas Sensor

Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan
Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
Author to whom correspondence should be addressed.
Received: 15 June 2014 / Revised: 7 August 2014 / Accepted: 26 August 2014 / Published: 2 September 2014
(This article belongs to the Special Issue Gas Sensors Based on the Field Effect)
Full-Text   |   PDF [4514 KB, uploaded 2 September 2014]


In this study, we investigate the keys to obtain a sensitive ammonia sensor with high air stability by using a low-cost polythiophene diode with a vertical channel and a porous top electrode. Poly(3-hexylthiophene) (P3HT) and air-stable poly(5,5'-bis(3-dodecyl-2-thienyl)-2,2'-bithiophene) (PQT-12) are both evaluated as the active sensing layer. Two-dimensional current simulation reveals that the proposed device exhibits numerous connected vertical nanometer junctions (VNJ). Due to the de-doping reaction between ammonia molecules and the bulk current flowing through the vertical channel, both PQT-12 and P3HT VNJ-diodes exhibit detection limits of 50-ppb ammonia. The P3HT VNJ-diode, however, becomes unstable after being stored in air for two days. On the contrary, the PQT-12 VNJ-diode keeps an almost unchanged response to 50-ppb ammonia after being stored in air for 25 days. The improved storage lifetime of an organic-semiconductor-based gas sensor in air is successfully demonstrated. View Full-Text
Keywords: ammonia; gas sensor; polythiophene; solid-state sensors ammonia; gas sensor; polythiophene; solid-state sensors
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Dai, M.-Z.; Chen, Y.-H.; Chuang, M.-Y.; Zan, H.-W.; Meng, H.-F. Achieving a Good Life Time in a Vertical-Organic-Diode Gas Sensor. Sensors 2014, 14, 16287-16295.

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