Quantum Dot Luminescence Microspheres Enable Ultra-Efficient and Bright Micro-LEDs.

Quantum dot (QD)-converted micrometer-scale light-emitting diodes (micro-LEDs) are regarded as an effective solution for achieving high-performance full-color micro-LED displays because of their narrow-band emission, simplified mass transfer, facile drive circuits, and low cost. However, these micro-LEDs suffer from significant blue light leakage and unsatisfactory electroluminescence properties due to the poor light conversion efficiency and stability of the QDs. Herein, the construction of green and red QD luminescence microspheres with the simultaneously high conversion efficiency of blue light and strong photoluminescence stability are proposed. These luminescence microspheres exhibit high external photoluminescence quantum yields exceeding 46% under 450 nm excitation, along with excellent reliability against blue light, heat, and water-oxygen degradation, owing to the waveguide and spatial confinement effects of the microspheres. The microsphere-based green and red micro-LEDs achieve world-record external quantum efficiencies of 40.8% and 22.1%, respectively, and high brightness values of 1.7 × 10 ⁸ and 7.6 × 10 ⁷  cd m ^-2 , respectively. Finally, 0.6 inch red, green, and blue monochrome micro-LED displays are demonstrated by integrating microsphere-converted micro-LED arrays with thin-film transistor backplanes, which show a pixel resolution as high as 1700 PPI and brightness exceeding 10 000 cd m ^-2 .
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