Materials provide efficient, sustainable emission technology news for OLEDs


A new 3D printing material for high-efficiency emitters could lead to a cheaper, more sustainable manufacturing process for OLED devices. The material, called supramolecular ink, demonstrates the ability to convert nearly all absorbed light into visible light during emission.

Although OLEDs are lighter, thinner, more energy-efficient and can provide higher-quality images than other flat-panel technologies, they often contain rare, expensive metals such as iridium. Supramolecular inks made from cheap, earth-abundant elements rather than expensive rare metals could make OLED displays and electronic devices cheaper and greener.

These 2-centimeter-tall 3D printed objects are made from supramolecular inks that emit blue or white light. Courtesy Jenny Nuss/Berkeley Lab & Science.


These 2-centimeter-tall 3D printed objects are made from supramolecular inks that emit blue or white light. Courtesy Jenny Nuss/Berkeley Lab & Science.


“By replacing precious metals with earth-abundant materials, our supramolecular ink technology could be a game-changer for the OLED display industry,” said Peidong Yang, a scientist in the Materials Sciences Division at Lawrence Berkeley National Laboratory (Berkeley Lab) and a professor at the university. UC Berkeley.

Developed by researchers at Berkeley Lab, the supramolecular ink consists of powders containing hafnium and zirconium that can be mixed in solution at room temperature or up to about 176°F to form a semiconductor ink composed of blue- and green-light emitting compounds. .

The ink contains tiny molecular structures that act as building blocks that self-assemble in solution through a process the team calls supramolecular assembly.

“Our method can be compared to the construction of Lego bricks,” said co-first author Cheng Zhu, a doctoral student at the University of California, Berkeley. The supramolecular structure enables stable, high-purity synthesis of the ink at low temperatures.

Single-crystal X-ray diffraction images of blue luminescent supramolecular ink (18C6@K)2HfBr6) reveal the atomic structure of the 1-2 nm unit cell. The structure of tiny molecular


Single crystal X-ray diffraction pattern of blue luminescent supramolecular ink (18C6@K)2Hafnium Bromide6) reveals the atomic structure of the 1 to 2 nm unit cell. The structure of tiny molecular “building blocks” in the ink self-assembles in solution, enabling the material to be synthesized stably and with high purity at low temperatures. Courtesy of Peidong Yang and Cheng Zhu/Berkeley Laboratory and Science Center.


In spectroscopy experiments conducted at the University of California, Berkeley, the supramolecular ink composites were shown to be highly efficient emitters of blue and green light, exhibiting near-unanimous quantum efficiencies. The hafnium powder composite exhibits a blue-emitting photoluminescence quantum yield of approximately 96%, while the zirconium analog exhibits a green-emitting photoluminescence quantum yield of approximately 83%. Researchers added a polymer to create solution-processable inks for printing luminescent films and structures. Highly emissive powders maintain high photoluminescence quantum yields in solution-processable semiconductor inks under ambient conditions.

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To demonstrate the material’s color tunability and luminescence as an OLED emitter, the researchers fabricated thin-film display prototypes with composite inks and demonstrated the material’s suitability for programmable electronic displays. Through other experiments conducted at UC Berkeley, the researchers demonstrated how to use supramolecular inks to achieve luminescent 3D-printed structures with high spatial resolution. The ink’s compatibility with 3D printing technology also makes it useful for designing decorative OLED lighting.

In addition to their potential role as energy-efficient OLED emitters for electronic displays and 3D printing, supramolecular inks can also be used to create high-tech clothing that illuminates individuals in low-light conditions, as well as wearable devices that display messages through supramolecular inks . structure. “The technology can also extend its applications to organic printable films for the manufacture of wearable devices as well as luminous art and sculptures,” Yang said.

A luminous structure in the shape of the Eiffel Tower, 3D printed with supramolecular ink. Each 2-centimetre-tall device is made from supramolecular ink that emits blue or green light when exposed to 254 nanometer ultraviolet light. Courtesy of Peidong Yang and Cheng Zhu/Berkeley Laboratory and Science Center.


A luminous structure in the shape of the Eiffel Tower, 3D printed with supramolecular ink. Each 2-centimetre-tall device is made from supramolecular ink that emits blue or green light when exposed to 254 nanometer ultraviolet light. Courtesy of Peidong Yang and Cheng Zhu/Berkeley Laboratory and Science Center.


Supramolecular inks could also help accelerate the commercialization of ionic halide perovskites in the display industry. Ionic halide perovskites are thin-film solar materials that can be synthesized in low-temperature solutions. Ionic halide perovskites can reduce the cost of the display manufacturing process, but high-performance halide perovskites contain lead.

Supramolecular inks belong to the ionic halide perovskite family and are based on high-performance, lead-free formulations that are safe for the environment and public health. Supramolecular ink compounds are stable and have a long shelf life.

Now, the team has identified the potential of supramolecular inks in OLED films and 3D printed electronics, and has begun exploring the material’s electroluminescent potential. “This involves focused and specialized research into our material’s ability to harness electrically stimulated luminescence,” Zhu said. “This step is critical to understanding the full potential of our material to create efficient light-emitting devices.”

The study was published in science (www.doi.org/10.1126/science.adi4196).



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