September 23, 2016

Flexible optical non-volatile memory

A precisely matched combination of a semiconducting polymer and photoactive molecules allowed the production of a highly efficient optical memory element. It is configured to save and delete information using light and not an electrical circuit as usual. One cell composed of such memory elements can store up to 256 times more information than existing memory elements.

These cells use the advantages offered by organic electronics. They are relatively simple to manufacture, flexible and useful, for example, in the manufacture of wearable electronics, electronic paper and other advanced electronic devices based on the organic semiconducting materials.

Organic nanomaterials are attracting a great deal of interest for use in flexible electronic applications such as logic circuits, displays and solar cells. These technologies have already demonstrated good performances, but flexible organic memories are yet to deliver on all their promise in terms of volatility, operational voltage, write/erase speed, as well as the number of distinct attainable levels.

They report a multilevel non-volatile flexible optical memory thin-film transistor based on a blend of a reference polymer semiconductor, namely poly(3-hexylthiophene), and a photochromic diarylethene, switched with ultraviolet and green light irradiation. A three-terminal device featuring over 256 (8 bit storage) distinct current levels was fabricated, the memory states of which could be switched with 3 ns laser pulses. We also report robustness over 70 write–erase cycles and non-volatility exceeding 500 days. The device was implemented on a flexible polyethylene terephthalate substrate, validating the concept for integration into wearable electronics and smart nanodevices.

The molecules’ fast response to a 3-nanosecond laser pulse matches modern electronics. Another benefit of the DAE molecules is that the number of molecules that are switched in reaction to the light can be precisely controlled—a key requirement for improved data density in multi-level storage.

The devices they have fabricated so far are laboratory prototypes, and thus are relatively large at 1 square millimeter. The researchers are already looking at shrinking and encapsulating the memory. They are also looking at roll-to-roll manufacturing and ink-jet printing.



Nature Nanotechnology - Flexible non-volatile optical memory thin-film transistor device with over 256 distinct levels based on an organic bicomponent blend





13 pages of supplemental material

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