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.