22 September 2005 Detection of a trace amount of impurity in smectic liquid-crystalline semiconductor
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An effective method for detecting a trace amount of chemical impurity, e.g., a few ppm or less, that degrades the charge carrier transport properties in smectic liquid crystalline (SmLC) semiconductors was investigated with a model system i.e., a 2-phenylnaphthalene derivative of 2-(dodecyloxy)-6-(4-octylphenyl)naphthalene (8-PNP-O12) and a terthiophene derivative of 2,5-bis(5-hexylthiophene-2-yl)thiophene (6-TTP-6). A transient photocurrent measurement could detect a chemical impurity of a few ppm or less that conventional analytical methods such as high-performance liquid chromatography (HPLC) and gas chromatography (GC) failed to detect: the slow transit induced by drift of ionized impurity molecules allowed us to detect it, which was clearly distinguished from the fast transit induced by the electronic conduction in the host SmLC semiconductor. This systematic study provided a semiquantitative basis for evaluating the contamination of chemical impurity.
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Hyonsoo Ahn, Akira Ohno, Jun-ichi Hanna, "Detection of a trace amount of impurity in smectic liquid-crystalline semiconductor", Proc. SPIE 5940, Organic Field-Effect Transistors IV, 594014 (22 September 2005); doi: 10.1117/12.614656; https://doi.org/10.1117/12.614656

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