Light and organic chemistry could make smarter, flexible devices | June 27, 2016 Issue - Vol. 94 Issue 26 | Chemical & Engineering News
Volume 94 Issue 26 | p. 7 | News of The Week
Issue Date: June 27, 2016 | Web Date: June 24, 2016

Light and organic chemistry could make smarter, flexible devices

A blend of organic materials bolsters bendable data storage devices
Department: Science & Technology
News Channels: Materials SCENE, Organic SCENE
Keywords: molecular electronics, materials, organic, transistor, memory
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A schematic of a new optoelectronic memory device that relies on the photoisomerization of diarylethene molecules (DAE) and semiconducting poly(3-hexylthiophene) (P3HT). The narrow portions of the topmost gold electrodes are about 50 μm wide.
Line structures show the open and closed form of a diarylethene molecule.
 
A schematic of a new optoelectronic memory device that relies on the photoisomerization of diarylethene molecules (DAE) and semiconducting poly(3-hexylthiophene) (P3HT). The narrow portions of the topmost gold electrodes are about 50 μm wide.

Flexible organic memory devices are now storing more information using light and divulging those data with electronic current.

These aren’t the first organic devices to use different physics for writing and reading data, but earlier devices were slower, stored fewer data, and degraded more quickly, say Paolo Samorì and Emanuele Orgiu of the University of Strasbourg. Chemistry has now allowed Samorì, Orgiu, Stefan Hecht of Humboldt University of Berlin, and their colleagues to overcome these limitations to build devices that could enable flexible, data-storing optoelectronic sensors and wearable electronics.

The team developed a blend of light-sensitive diarylethene molecules and poly(3-hexylthiophene), a semiconducting polymer. When excited by ultraviolet light, diarylethene molecules change from an open form to a closed one. This chemistry allows the team to quickly “write” information in the molecular blend with nanosecond-long laser pulses. The diarylethene molecules can be reopened with visible light to erase data.

The ratio of opened to closed molecules influences how the poly(3-hexylthiophene) shuttles electronic charge, measured as a current. Each light pulse changes the current by a distinct interval, creating devices with at least 256 discrete current levels or memory states, many more than previously achieved with similar devices (Nat. Nanotechnol. 2016, DOI: 10.1038/nnano.2016.87).

Furthermore, the new devices can reliably store data for hundreds of days, even when disconnected from a power source, the team says.

 
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