Improvement of Quantum Dot Light-Emitting Diodes (QD-LED) with Photonic Crystals

Abstract

Quantum dots (QDs) are known as key materials in next-generation displays. They have high quantum efficiency and narrow full width at half maximum (FWHM), which enables fabrication of highly efficient display with wider color gamut than other displays. To increase light extraction and material utilization of QDs in a display, photonic crystals with desired photonic stopband are introduced into light-emitting diodes (LEDs). While the photonic crystal stopband matches excitation peak (i.e. 450 nm from blue LED), green and red emitting QDs in LEDs can be largely improved via excitation photons resonance. Therefore, it is promising to prepared a high intensity QD-LED with low QD usage, reducing cost and tiny amount of cadmium, to produce a more environment-friendly and competitive QD-LED products. However, conventional preparation processes of photonic crystals are time-consuming and difficult to scale-up. For example, photonic crystal thin films are generally prepared by vertically deposition self-assembly or laser interference lithography methods are not suitable to mass production QD-LEDs. In this research, a facile method to prepare photonic QD-LED have been investigated. The inverse photonic crystal with stopband at 450 nm in PDMS was fabricated by centrifuge self-assembly, forced impregnation with titanium butoxide and calcination at 550 oC for 6h. A photonic QD glue was prepared by mixing inverse photonic crystal, quantum dot and PDMS. After vacuum degassing, a photonic QD-LED was fabricated by dispensing the glue and cured at 120 oC for 30 min. The photonic QD-LED has shown a 22% increase in the luminescence intensity than that of general QD-LEDs with conventional scatter particles.