How bright can the new perovskite light-emitting diode shine?
Research and innovation hub imec in Belgium has created a new type of perovskite LED (PeLED) stack that shines 1 000 times brighter than state-of-the-art organic LEDs (OLEDs). Part of the EU-funded ULTRA-LUX project, the achievement is – as the imec team describes in an ‘Optics.org’ news item – a “pivotal milestone towards a perovskite injection laser, promising exciting applications in image projection, environmental sensing, medical diagnostics, and beyond.” Currently used in applications ranging from television and computers to traffic signals and aviation lighting, LEDs have revolutionised modern lighting and sensing technology. OLEDs – which are widely used to create digital displays in television screens, computer monitors, smartphones and handheld game consoles – utilise organic thin-film polymers as semiconductors. However, these have limited peak brightness. Remember how difficult it is to read your smartphone screen when you are out in the sun? This is where perovskites come in. A calcium titanium oxide mineral with a cubic crystal structure, perovskite has unusual physical properties that could find use in applications beyond solar cells – currently its most prominent application. Over the last decade, its excellent optoelectrical properties, low-cost processability and efficient charge transport have led to perovskite being recognised as a promising candidate for LED applications.
PeLED in the spotlight
However, as the news item explains, perovskites may be able to resist significantly high current densities, but laser operation with the emission of high-intensity coherent light has not yet been achieved. “In the 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”, remarks imec senior fellow Prof. Paul Heremans, who is a corresponding author of the study published in ‘Nature Photonics’. “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 (3 kA cm-2) than conventional OLEDs can,” Prof. Heremans adds. So what has been achieved with this new architecture? imec Project Manager Robert Gehlhaar, also a corresponding author on the study, explains: “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 per cent to the total amount of stimulated emission and thus approaches the threshold to achieve a thin-film injection laser. Reaching this landmark milestone towards high-power thin-film laser diodes is paving the way to exciting new applications of thin-film perovskite lasers.” The ULTRA-LUX (Ultra-Bright Thin-Film Light Emitting Devices and Lasers) projects ends in September 2024. For more information, please see: ULTRA-LUX project
Keywords
ULTRA-LUX, perovskite, light-emitting diode, LED, organic LED, perovskite LED, laser
