Direct Imaging and Probing of the p鈭抧 Junction in a Planar Polymer Light-Emitting Electrochemical Cell
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文摘
A vast array of semiconductor applications relies on the ability to dope the materials by the controlled introduction of impurities in order to achieve desired charge carrier concentration and conduction type. In this way, various functional metal/semiconductor or semiconductor/semiconductor junctions can be constructed for device applications. Conjugated polymers are organic semiconductors that can be electrochemically doped to form a dynamic p鈭抧 junction. The electronic structure and even the existence of such a polymer p鈭抧 junction had been the subject of intense scrutiny and debate. In this work, the formation of the world鈥檚 largest frozen polymer p鈭抧 junction and its light-emission are visualized. With a pair of micromanipulated probes, we mapped the potential distribution of the p鈭抧 junction under bias across the entire interelectrode gap of over 10 mm. Site-selective current鈭抳oltage measurements reveal that the polymer junction is a graded p鈭抧 junction, with a much more conductive p region than n region.