Researchers at the CEA-Leti institute (a MicroLED Association member institute) developed green and red-emitting thin-film perovskite color conversion layers (CCLs) using pulsed laser deposition (PLD), that can be used in microLED microdisplays.
The researchers say that while QDs provide a good solution for color conversion microLED displays, they suffer from low absorption, which means that require a thicness of 3-10 micron, which is a challnge for very small microLEDs, required for microdisplays.
The new technology, uses inorganic halide perovskites (CsPbBr₃ for green, CsPbI₂Br for red) to offer direct bandgap, high absorption (~10⁵ cm⁻¹), narrow emission (FWHM 17nm at 516nm green, 31nm at 640nm red), and tunable composition. Deposited via PLD on 200mm wafers at room temperature, they outperform InP QDs in purity and offer high uniformity. Theoretical microLEDs with these CCLs plus filters cover 90% of Rec. 2020 gamut (CIE: green 0.100,0.785; red 0.704,0.296; blue 0.140,0.048), with green needing minor wavelength shift via composition engineering.
At 450nm, absorption reaches 4.6×10⁴ cm⁻¹ (CsPbBr₃) and 6.4×10⁴ cm⁻¹ (CsPbI₂Br) – up to 20x higher than InP QDs - enabling 90% blue light absorption at just 500nm (green) or 360nm (red) thicknesses. This supports <1μm pixel pitches with and easy patterning.
In first experiments, CsPbBr₃ films maintain stable emission wavelength and FWHM from 0.06 to 715 W/cm² (375nm laser) - exceeding AR/MR needs (~1 W/cm² for 100k nits) by three orders of magnitude, proving to have high potential for low QD degradation under flux or moisture. Further testing is required to determine stability for longer time periods.
Anyone that wishes to contact the researchers at CEA Leti can reach out to the lead researcher, Dr. François Templier, at ftemplier@cea.fr.
