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Understanding the underlying physics of charge transport in organic semiconductors under illumination is important for the development of novel optoelectronic applications. We study the effects of monochromatic light in the visible spectrum on the channel of an organic thin-film transistor based on 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene. When the channel of the transistor was illuminated with red, green, or blue light, more charge carriers were measured than what exciton generation from photon absorption alone could provide, leading to a photon-to-charge-carrier conversion efficiency much larger than 100%. We explain this phenomenon using a model incorporating space-charge limited photocharges and enhanced hole injection from the source electrode due to lowering of the potential barrier by photogenerated electrons.
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Voltage controlled bio-organic inverse phototransistor
Thin films of poly-d-lysine act as polar organic and are also light sensitive. The capacitance-voltage, current-voltage, and transistor behavior were studied to gauge the photoresponse of possible poly-d-lysine thin film devices both with and without methylene blue as an additive. Transistors fabricated from poly-d-lysine act as inverse phototransistors, i.e., the on-state current is greatest in the absence of illumination. The poly-d-lysine thin film capacitance and the transistor current decrease with illumination, both with and without methylene blue as an additive. This suggests that the unbinding of photo exciton is significantly hindered in this system which is supported by the significant charge carrier lifetime for poly-d-lysine films both with and without methylene blue. For the majority carrier, the transistor geometry appears to depend on the gate voltage; in other words, the majority carrier depends on the polarization of the poly-d-lysine films, both with and without methylene blue as an additive.
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- PAR ID:
- 10364061
- Publisher / Repository:
- American Vacuum Society
- Date Published:
- Journal Name:
- Biointerphases
- Volume:
- 17
- Issue:
- 2
- ISSN:
- 1934-8630
- Page Range / eLocation ID:
- Article No. 021003
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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