FOCUS BUSINESS AND RESEARCH NEWS
Perovskite LED lasers ‘1000x brighter than OLED’
B
elgian research institute Imec has developed a perovskite LED (PeLED) stack that emits light a thousand times brighter than
state-of-the-art OLEDs. This result, published in Nature
Photonics in January, represents a milestone towards developing a perovskite injection laser, which promises exciting applications in image projection, environmental sensing, medical diagnostics, and beyond. Perovskites offer excellent
optoelectrical properties, low-cost processability and efficient charge transport. They have emerged in the past 10 years as interesting candidates for light emission
applications, such as LEDs, with limited brightness. However, while perovskites can withstand very high current densities, laser operation with the emission of high- intensity coherent light has not yet been reached. As part of the European Research Council-funded Ultra-Lux project, Imec showed for the first time a PeLED architecture with low optical losses, and pumped these PeLEDs to current densities that support the stimulated emission of light. “This novel architecture of transport
layers, transparent electrodes and perovskite as the semiconductor active material, can operate at electrical current densities tens of thousands of times higher (3kA/cm2
) than conventional OLEDs can,”
said Professor Paul Heremans, an Imec Senior Fellow and principal investigator of the project. With this architecture, Imec enhanced amplified spontaneous emission, with an electrical assist of the conventional optical pumping. “By doing so, Imec demonstrated that electrical injection contributes 13% to the total amount of stimulated emission and thus approaches the threshold to achieve a thin film injection laser”, said Robert Gehlhaar, Imec project manager. “Reaching this landmark milestone
towards high-power thin-film laser diodes is paving the way to exciting new applications of thin-film perovskite lasers.”
Transfer printing method to speed up manufacture of OLEDs
A
team at the Korea Advanced Institute of Science and Technology (Kaist) has developed a micro-vacuum
assisted selective transfer printing (µVAST) technology that could help overcome the challenges associated with manufacturing OLEDs. Transfer printing technology is used during the manufacture of OLEDs, for rearranging microLED dies from a growth substrate onto the final substrate with a desired layout and precise alignment. However, previous transfer methods still have many challenges such as the need for additional adhesives, misalignment, low transfer yield, and chip damage. Kaist’s key technology relies on a
laser-induced etching (LIE) method for forming 20µm-sized micro-hole arrays with a high aspect ratio on glass substrates at fabrication speed of up to 7,000 holes per second. The LIE- drilled glass is connected to the vacuum channels, controlling the micro-vacuum force at desired hole arrays to selectively pick up and release the microLEDs. The micro-vacuum assisted
transfer printing accomplishes a higher adhesion switchability compared with previous transfer methods, enabling the assembly of micro-sized semiconductors with various heterogeneous materials, sizes, shapes, and thicknesses onto arbitrary substrates with high transfer yields.
www.electrooptics.com
February2024 Electro Optics
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