Photoluminescent image of the California Golden Bears logo emitted by five-element ZrSnTeHfPt single crystals under UV lamp excitation. Image: Maria Folgueras and Peidong Yang/Berkeley Lab.
Photoluminescent image of the California Golden Bears logo emitted by five-element ZrSnTeHfPt single crystals under UV lamp excitation. Image: Maria Folgueras and Peidong Yang/Berkeley Lab.

Semiconductors are the heart of almost every electronic device. Without semiconductors, our computers would not be able to process and retain data, and LED (light-emitting diode) lightbulbs would lose their ability to shine.

But semiconductor manufacturing requires a lot of energy. Synthesizing semiconductor materials from sand (silicon oxide) consumes a significant amount of heat-intensive energy, at scorching temperatures of around 2700°F. And the process of purifying and assembling all the raw materials that go into making a semiconductor can take weeks if not months.

A new semiconducting material called ‘multielement ink’ could make that process significantly less heat-intensive and more sustainable. Developed by researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, multielement ink is the first ‘high-entropy’ semiconductor that can be processed at low temperatures. The researchers report this breakthrough in a paper in Nature.

“The traditional way of making semiconductor devices is energy-intensive and one of the major sources of carbon emissions,” said Peidong Yang, a faculty senior scientist in Berkeley Lab’s Materials Sciences Division, a professor of chemistry and materials science and engineering at UC Berkeley and senior author of the paper. “Our new method of making semiconductors could pave the way for a more sustainable semiconductor industry.”

The advance takes advantage of two unique families of semiconducting materials: hard alloys made of high-entropy semiconductors; and a soft, flexible material made of crystalline halide perovskites.

High-entropy alloys are solids made of five or more different metallic elements that self-assemble in near-equal proportions into a single system. For many years, researchers have wanted to use high-entropy alloys to develop semiconducting materials that self-assemble with minimal energy inputs.

“But high-entropy semiconductors have not been studied to nearly the same extent,” said Yuxin Jiang, a graduate student researcher in Yang’s groups at Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Department of Chemistry, and co-first author of the paper. “Our work could help to significantly fill in that gap of understanding.”

Although conventional high-entropy alloys require far less energy than silicon to process for manufacturing, they still demand very high temperatures of over 1000°C (1832°F). Scaling up high-entropy materials for industrial-scale manufacturing is challenging because of this enormous energy input.

To overcome this hurdle, Yang and team leveraged the unique qualities of a well-studied solar material that has intrigued researchers for many years: halide perovskites.

Perovskites are easily processed from solution at low temperatures – from room temperature to around 300°F. These lower processing temperatures could one day dramatically reduce energy costs for semiconductor manufacturers.

For the new study, Yang and his team took advantage of this lower-energy requirement to synthesize high-entropy halide persovskite single crystals from a solution under room-temperature or low-temperature (80°C or 176°F) conditions. Because of their ionic bonding nature, halide perovskite crystal structures require significantly lower energy to form, compared with other material systems.

Experiments at Berkeley Lab’s Advanced Light Source confirmed that the resulting octahedral and cuboctahedral crystals are high-entropy halide perovskite single crystals: one set made of five elements (SnTeReIrPt or ZrSnTeHfPt), and another set made of six elements (SnTeReOsIrPt or ZrSnTeHfRePt). The crystals are approximately 30–100µm in diameter.

This low-temperature/room-temperature technique produces single-crystal semiconductors within hours of mixing a solution and precipitating, far faster than conventional semiconductor fabrication techniques.

“Intuitively, making these semiconductors is like stacking octahedral-shaped molecular ‘LEGOs’ into larger octahedral single crystals,” said Yang. “Imagining each of these individual molecular LEGOs will emit at different wavelengths, one can in principle design a semiconductor material that would emit an arbitrary color by selecting different molecular octahedral LEGOs.” The authors demonstrated this concept by printing a California Golden Bears logo.

Stability at ambient temperature has long been a problem for advancing commercial-ready halide perovskites. But in a benchtop experiment for the new study, the high-entropy, multielement ink halide perovskite surprised the research team with an impressive ambient-air stability of at least six months.

According to Yang, the multielement ink has a number of potential applications, particularly as a color-tunable LED or other solid-state lighting device, or as a thermoelectric for waste heat recovery. In addition, the material could potentially serve as a programmable component in an optical computing device that uses light to transfer or store data.

“Our high-entropy halide-perovskite semiconductor crystals, with their room-temperature and low-temperature methods, can be incorporated into an electronic device without destroying the other necessary layers, thus allowing for easier design of electronic devices and for more widespread use of high-entropy materials in electronic devices,” said Maria Folgueras, a former graduate student fellow in Yang’s groups at Berkeley Lab and UC Berkeley and co-first author of the paper.

“One can imagine that each of these octahedral LEGOs could carry some type of ‘genetic’ information, just like DNA base pairs carry our genetic information,” Yang said. “It would be quite fascinating if one day we could code and decode these molecular LEGO semiconductors for information-science applications.”

The researchers plan to continue designing sustainable semiconductor materials for solid-state lighting and display applications.

This story is adapted from material from Lawrence Berkeley National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.