pinMOS memory can be written and read optically or electrically

28 Nov 2019

Researchers in Dresden have developed a new storage tech based on an organic light-emitting diode and an insulator.

Scientists at Dresden's Integrated Center for Applied Physics & Photonic Materials and the city's Center for Advancing Electronics Dresden at TU Dresden have developed a novel storage technology based on the combination of an organic light-emitting diode and an insulator.

This device allows reading stored information optically as well as electrically. Moreover, the information can be added in portions – thus several storage states can be mapped in one device. The results have now been published in Advanced Functional Materials.

Another novelty was related to the measurements in the test series: They were carried out exclusively using the innovative "SweepMe!" measuring software, which was developed by an IAPP/cfaed start-up of the same name.

In 2015, Prof. Stefan Mannsfeld, Chair of Organic Devices at cfaed / IAPP, shared a development idea with Dr. Axel Fischer, Chair of Organic Semiconductors, IAPP, that had kept him busy for a while.

The combination of a conventional OLEDs with an insulator layer would have to result in a storage unit due to the specific physical effects of the materials used, which could be written on and read out using both light and electrical signals: a misappropriated use of the OLED technology so to speak.

Dr. Fischer confirmed that the necessary technologies and experience were already available at the IAPP – and so the investigation of this idea was only a matter of time. Yichu Zheng at Prof. Mannsfeld's chair was a suitable candidate to dedicate her doctoral thesis to this topic.

Storing and reading with light and electricity

The scientists describe a new type of programmable organic capacitive memory, which is a combination of an OLED and a MOS capacitor (metal oxide semiconductor). The storage unit called pinMOS is a non-volatile memcapacitor with high repeatability and reproducibility.

Its special capability is that pinMOS is able to store several states simultaneously, since charges can be added or removed in controllable amounts. Another attractive feature is that this simple diode-based memory can be both electrically and optically written to and read from.

Currently, a lifetime of more than 104 read-write erase cycles is possible, and the memory states can be maintained and differentiated over 24 hours. Experimental results show that the pinMOS memory principle as a reliable capacitive storage medium is promising for future applications in electronic and photonic circuits such as neuromorphic computers or visual storage systems.

The co-authors of the Weierstraß Institute Berlin (WIAS) were able to contribute to the precise interpretation of the functional mechanism by performing drift diffusion simulations.

Measuring with SweepMe!

All measurements within this study were performed with the new laboratory measurement software SweepMe!. This software has been developed by a start-up of the same name, which is also a spin-off from TU Dresden. The physicists Axel Fischer and Felix Kaschura who received their PhDs from TUD founded SweepMe! in 2018 at the IAPP.

The researchers concluded, "This study proved how versatile SweepMe! can be. Whether the measurement of voltage-dependent and time-dependent capacitances, the creation of current-voltage characteristics, the combination of signal generator and oscilloscope or the processing of images from an industrial camera. Everything was implemented with this single software package."