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Title: | Organic Field Effect Transistor Semiconductor Blends for Advanced Electronic Devices Including UV Phototransistors and Single Walled Carbon Nanotube Enhanced Devices |
Other Titles: | OFET Semiconductor Blends for Advanced Electronic Devices |
Authors: | Smithson, Chad |
Advisor: | Zhu, Shiping Wu, Yiliang |
Department: | Chemical Engineering |
Keywords: | SWCNT;Single Walled Carbon Nanotubes;Unsorted Single Walled Carbon Nanotubes;DPP-QT;OFET;Organic Field Effect Transistor;Printed Electronics;Phototransistor;UV Responsive;Organic Sensor;Printed Sensor;BTBT |
Publication Date: | Nov-2015 |
Abstract: | Two major projects involving the use of solution processed blended semiconductors for organic field effect transistors (OFET) were explored. The first incorporated unsorted single walled carbon nanotubes (SWCNTs) into a diketopyrrolopyrrole-quarterthiophene (DPP-QT) semiconductor to enhance the mobility of the OFET. 2 wt % SWCNT was found to be the optimal blend ratio, nearly doubling the device mobility (0.6 to 0.98 cm^2/V·s). Beyond this ratio, the metallic content of the SWCNT’s dropped the on/off ratio below acceptable levels. When source drain metals who’s work function poorly matched that of the DPP-QT semiconductors highest occupied molecular orbital (HOMO) were used, the SWCNT could dramatically reduce the charge injection ratio with best results achieved for Al, dropping the contact resistance from 10^5 to 45 MΩ. The second project explored the addition of small molecule additives into a UV-sensitive semiconductor 2,7-dipentyl[1]benzothieno[3,2-b][1] benzothiophene (C5-BTBT) mixed with a polymethyl methacrylate (PMMA) polymer binder. We generated a C5-BTBT based phototransistor sensitive to UV-A light. The HOMO and lowest unoccupied molecular orbital (LUMO) of C5-BTBT and the various additives were measured and discovered to play a critical role in how the device operates. We discovered if an additive has a LUMO lower in energy than C5-BTBT, it can act as a charge trap for a photogenerated electron. Electron deficient additives were found to retain a trapped electron for an extended period of time, allowing the device to remain in a high current state for an extended period of time (>1 hour). This provides an opportunity for the device to be used as an optical memory system or photoswitch. The best system could detect UV-A with a Pill > 10^5 and a photoresponsivity of 40 A/W at a Pinc of 0.0427 mW/cm^2. |
URI: | http://hdl.handle.net/11375/18154 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Smithson_Chad_S_201509_PhD.pdf | PhD Thesis Chad Steven Smithson | 10.89 MB | Adobe PDF | View/Open |
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