Will 2D material innovation soothe ‘green gap’ headache?

Technology News |
By eeNews Europe

The technology is claimed to provide a solution for a key technical problem with LEDs used today in lighting and with laser diodes. VerLASE has shown for the first time a novel, commercially feasible way to grow Wurtzite phase II-VI crystal films.

Currently, the primary light emitting technology for much of the visible spectrum is based on gallium nitride and its variants, but these materials tend to natively produce only blue or violet light. To get true green, yellow, and red colors, or mix them for white, the color that is directly emitted must be converted with the help of various phosphors, which can include Quantum Dots (QDs). Such down conversion to longer wavelength colors results in some loss in efficiency and increased thermal effects. Traditional phosphors are also temperature sensitive, causing color shifts, brightness degradation, reduced lifetimes, and other problems. Moreover, they tend to emit over a broader band with suboptimal colors and poorer color saturation, and suffer large variability in the manufacturing process.

VerLASE has instead been working with so-called II-VI materials, ironically well-known light emitters that had been extensively researched in the past before Gallium Nitride took the stage. II-VI materials can directly emit colors in the visible spectrum where Gallium Nitride cannot, efficiently closing the ‘green/yellow’ gap in the industry. They are, in fact, the same materials typically used in many of today’s QDs used as phosphors or color enhancement films in the visible spectrum. The problem with II-VI materials in the past had been very short lifetimes due to extensive defects in the materials stemming from how they were grown, and in the crystalline phase in which they were grown, a so-called Zinc Blende phase. The issued patent reveals how to grow such materials in a hitherto very difficult to attain Wurtzite phase by using certain layered 2D materials as templates. The Wurtzite phase is far more robust and resistant to defect formation than the Zinc Blende phase, enabling practical light emitting devices to be made based on semiconductor Quantum Wells (QWs) of these materials.

“This is a key innovation for several important applications,” suggested Professor Maria Tamargo, Professor of Chemistry at the City College of the City University of New York, and a leading expert on II-VI materials and devices, adding that “VerLASE has shown for the first time a novel, commercially feasible way to grow Wurtzite phase II-VI crystal films, a focus area of research worldwide”

“Using certain layered 2D materials enables us to grow II-VI based QWs for a variety of devices,” said Ajay Jain, VerLASE’s Chief Technical Officer and inventor of the technology, adding his appreciation to a number of collaborators who had helped demonstrate the process.

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