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Doping organic semiconductors has become a key technology to increase the performance of organic light-emitting diodes, solar cells, or field-effect transistors (OFETs). However, doping can be used not only to optimize these devices but also to enable new design principles as well. Here, a novel type of OFET is reported—the vertical organic tunnel field-effect transistor. Based on heterogeneously doped drain and source contacts, charge carriers are injected from an n-doped source electrode into the channel by Zener tunneling and are transported toward a p-doped drain electrode. The working mechanism of these transistors is discussed with the help of a tunnel model that takes energetic broadening of transport states in organic semiconductors and roughness of organic layers into account. The proposed device principle opens new ways to optimize OFETs. It is shown that the Zener junction included between the source and drain of the vertical organic tunnel field-effect transistors suppresses short channel effects and improves the saturation of vertical OFETs.
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Efficiency enhancement of organic thin-film phototransistors due to photoassisted charge injection
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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- PAR ID:
- 10594970
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 119
- Issue:
- 7
- ISSN:
- 0003-6951
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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