IMEC makes perovskite LEDs 1,000 times brighter than OLED
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Nanoelectronics research institute IMEC has reported a metal-halide perovskite LED stack that is 1,000 times brighter than OLEDs and a candidate laser material.
Organic LEDs are more easily manufactured and assembled as displays than III-V LEDs but have the disadvantage of being about 300 times less bright. IMEC (Leuven, Belgium) has published a paper on a perovskite material that can transcend that limitation and can generate gain in the form of amplified spontaneous emission.
Perovskite-structured materials are those a crystal structure similar to CaTiO3. They also display excellent optoelectrical properties, efficient charge transport – meaning they can sustain high currents – and low-cost processing.
They are already proving their worth in photovoltaic applications. If they can be stacked to form laser diodes at brightnesses comparable with or exceeding conventional III-V laser diodes it promises applications in image projection, environmental sensing and medical diagnostics.
Ultra-Lux
IMEC has shown a transparent perovskite LED (PeLED) material under the auspices of the Ultra-Lux project and reported in Nature Photonics. The researchers used 2.3ns optical pulses at 77K and achieved amplified spontaneous emission. With longer sub-microsecond pulses the researchers achieved current densities of 3kA per square centimeter and irradiance values of 40W per square centimeter.
The research leader on the project is IMEC fellow Professor Paul Heremans. He said: “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. He added: “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 than conventional OLEDs can.”
Robert Gehlhaar, IMEC project manager, said that IMEC has demonstrated that electrical injection contributed 13 percent of the total amount of stimulated emission and that therefore the structure is approaching the threshold for a thin-film injection laser.
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