title: Achieving a good life time in a vertical-organic-diode gas sensor.
abstract: 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.
authors.affiliation: Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan. whiffet_tw@hotmail.com.
authors.forename: Ming-Zhi
authors.initials: MZ
authors.lastname: Dai
authors.affiliation: Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan. patrickyoyo0624@hotmail.com.
authors.forename: Yen-Ho
authors.initials: YH
authors.lastname: Chen
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan. a524524524@livemail.tw.
authors.forename: Ming-Yen
authors.initials: MY
authors.lastname: Chuang
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan. hsiaowen@mail.nctu.edu.tw.
authors.forename: Hsiao-Wen
authors.initials: HW
authors.lastname: Zan
authors.affiliation: Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan. meng@mail.nctu.edu.tw.
authors.forename: Hsin-Fei
authors.initials: HF
authors.lastname: Meng
mesh_terms: D000641:Ammonia / Q000032:analysis*; D003217:Conductometry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005740:Gases / Q000032:analysis*; D016566:Organoselenium Compounds / Q000737:chemistry*; D012666:Semiconductors; D013876:Thiophenes / Q000737:chemistry*; D014159:Transducers
chemical_list: D005740:Gases; D016566:Organoselenium Compounds; D013876:Thiophenes; C526212:poly(3-hexyl)selenophene; D000641:Ammonia