One material with two functions could lead to faster memory
Researchers use perovskite to develop a memory device readable through
both electrical and optical methods

Date:
August 23, 2021
Source:
Kyushu University
Summary:
Researchers have developed a new light-emitting memory device by
integrating a resistive random-access memory with a light-emitting
electrochemical cell that are both based on perovskite. The
results are promising for faster data storage and reading in
future electronic devices and open a new avenue of applications
for perovskite optoelectronics.



FULL STORY ==========================================================================
In a step toward a future of higher performance memory devices,
researchers from National Taiwan Normal University and Kyushu University
have developed a new device that needs only a single semiconductor known
as perovskite to simultaneously store and visually transmit data.


==========================================================================
By integrating a light-emitting electrochemical cell with a resistive
random- access memory that are both based on perovskite, the team achieved parallel and synchronous reading of data both electrically and optically
in a 'light- emitting memory.' At the most fundamental level, digital
data is stored as a basic unit of information known as a bit, which is
often represented as either a one or a zero. Thus, the pursuit of better
data storage comes down to finding more efficient ways to store and read
these ones and zeros.

While flash memory has become extremely popular, researchers have been searching for alternatives that could further improve speed and simplify fabrication.

One candidate is nonvolatile resistive random-access memory, or
RRAM. Instead of storing charge in transistors like in flash memory,
resistive memory uses materials that can switch between states of high
and low resistance to represent ones and zeros.

"However, the electrical measurements needed to check the resistance and
read zeros and ones from RRAM can limit the overall speed," explains
Chun-Chieh Chang, professor at National Taiwan Normal University and
one of the corresponding authors of the study published in Nature Communications.



========================================================================== "Recently, to overcome this issue, RRAMs have been combined with LEDs
to develop something called light-emitting memories. In this case,
the data can also be read by checking if the LED is on or off. This
additional optical reading also opens new routes for carrying large
amounts of information." However, previous versions of light-emitting
memories required the integration of two separate devices with differing materials, complicating fabrication.

To overcome this, the researchers turned to perovskite, a type of material
with a crystalline structure through which ions can migrate to give it
unique physical, optical, and even electrical properties. By controlling
the ion migration, perovskite researchers have been constructing new
materials with unique properties.

"Using just one perovskite layer between contacts, we could fabricate a
device that works both as a RRAM and a light-emitting electrochemical
cell," explains National Taiwan Normal University's Ya-Ju Lee, who
also led the study. "By taking advantage of the fast, electrically
switchable ionic motion that enables this dual functionality in a single
layer of perovskite, we were able to connect two devices together
and develop an all-inorganic perovskite light- emitting memory."
Using perovskite consisting of cesium lead bromide (CsPbBr3), the team demonstrated that data can be electrically written, erased, and read in
one of the perovskite devices acting as an RRAM. Simultaneously, the
second perovskite device can optically transmit whether data is being
written or erased through light emission by working as a light-emitting electrochemical cell with a high transmission speed.

Furthermore, the researchers used perovskite quantum dots of two different sizes for the two devices in the light-emitting memory to achieve
different emission colors depending on whether the memory was being
written or erased, providing a real-time indicator of the ones and zeros.

Kaoru Tamada, a distinguished professor at Kyushu University's Institute
for Materials Chemistry and Engineering who was also involved in the
project, sees many opportunities for this new technology going forward.

"This demonstration significantly broadens the scope of applications of
the developed all-perovskite light-emitting memory and can serve as a
new paradigm of synergistic combination between electronic and photonic
degrees of freedom in perovskite materials," says Tamada.

"From multicast mesh network to data encryption
systems, these findings have the potential for
numerous applications in next-generation technologies." ========================================================================== Story Source: Materials provided by Kyushu_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Meng-Cheng Yen, Chia-Jung Lee, Kang-Hsiang Liu, Yi Peng, Junfu
Leng, Tzu-
Hsuan Chang, Chun-Chieh Chang, Kaoru Tamada, Ya-Ju
Lee. All-inorganic perovskite quantum dot light-emitting
memories. Nature Communications, 2021; 12 (1) DOI:
10.1038/s41467-021-24762-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210823085623.htm

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