A high-sensitivity near-infrared phototransistor based on an organic bulk heterojunction
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摘要High-gain photodetectors with near-infrared (NIR) sensitivity are critical for biomedical applications such as photoplethysmography and optical coherence tomography where detected optical signals are relatively weak. Current photodetection technologies rely on avalanche photodiodes and photomultipliers to achieve high sensitivity. These devices, however, require a high operation voltage and are not compatible with CMOS based read-out circuits (ROCs). In this work we demonstrate a solution-proceeded NIR phototransistor structure based on a bulk heterojunction (BHJ) of a narrow bandgap polymer, poly(N-alkyl diketopyrrolo-pyrrole dithienylthieno[3,2-b] thiophene) (DPP-DTT), and [6,6]-phenyl-C61-butyric acid methylester (PCBM). The device exhibits ultrahigh responsivity (similar to 5 x 10(5) A W-1) as well as wide tunability (>1 x 10(4)) of photoconductive gain. Using the current-voltage and transient photocurrent measurements we show that the high responsivity is due to the combined effects of fast transport of holes in the polymer matrix and slow detrapping of electrons from the isolated PCBM domains. The wide gain tunability and the efficient suppression of noise current are achieved through the use of the optically tunable gate terminal. We demonstrate that our phototransistor can be used as the detection unit in a photoplethysmography sensor for non-invasive, continuous finger pulse wave monitoring. The high-sensitivity of the phototransistor allows the use of a low-power light source, thus reducing the overall power consumption of the sensor. This, together with the solution processibility and the simple device configuration (which is compatible with conventional ROCs), make the phototransistor a very promising component for the next generation low-cost, mobile biomedical devices for health monitoring and remote diagnostics.
著者Xu HH, Li J, Leung BHK, Poon CCY, Ong BS, Zhang YT, Zhao N
期刊名稱Nanoscale
出版年份2013
月份1
日期1
卷號5
期次23
出版社Royal Society of Chemistry
頁次11850 - 11855
國際標準期刊號2040-3364
電子國際標準期刊號2040-3372
語言英式英語
Web of Science 學科類別Chemistry; Chemistry, Multidisciplinary; CHEMISTRY, MULTIDISCIPLINARY; Materials Science; Materials Science, Multidisciplinary; MATERIALS SCIENCE, MULTIDISCIPLINARY; Nanoscience & Nanotechnology; NANOSCIENCE & NANOTECHNOLOGY; Physics; Physics, Applied; PHYSICS, APPLIED; Science & Technology - Other Topics

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