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A high ambient contrast ratio (ACR) is essential for achieving a high dynamic range in advanced display applications, but reported ACR enhancement strategies always result in reduced optical efficiency of light-emitting diode (LED) display devices. In this study, an Fe3O4-magnetic particle-chained pillar array (Fe3O4-MPCP) structure was introduced to improve the ACR of LED display devices with low optical loss. The results indicated that the MPCP structure achieved high ACR at an oblique angle using surface pillar array to suppress ambient light reflections, and its internal magnetic particle chain improved the transmissivity to maintain high device efficiency. Compared with the commercial graphite-coated device at typical viewing angles (i.e., 0 deg and 60 deg), the ACR of the optimal MPCP device increased by 217 and 140%, while the device efficiency increased by 25 and 12%, respectively. Therefore, the proposed method provides a novel approach for significantly improving ACR at all oblique angles while maintaining high device efficiency, which can be easily integrated into various LED display devices and has significant potential in advanced display applications.

Mini full-color light-emitting diodes (mini-fc-LEDs) are a promising solution for display applications, including outdoor, cinema, and wearable devices, owing to their high resolution. However, it is difficult to simultaneously obtain high color uniformity and ambient contrast ratio (ACR). To solve this issue, we report a bilayered packaging structure with an SiO2 scattering layer on the bottom and a graphite extinction layer on the top. The bilayered packaging structure combines the scattering effect of SiO2 nanoparticles and the extinction effect of graphite nanoparticles, wherein the scattering effect improves the color uniformity, and the extinction effect improves the ACR. The color uniformity and ACR of the mini-fc-LEDs were selectively adjusted by changing the nanoparticle concentration and the thickness ratio of the bilayer. Compared to conventional devices, the inhomogeneity of the bilayered devices reduced by 65.9%, the ACR increased by 32.9%, and the figure of merit (FOM, representing the overall performance of the device) increased by 168.8%. We believe that the proposed packaging structure can also be applied to other LEDs such as OLEDs and micro-LEDs.

Inverted packaging structure is a promising alternative for thermal isolation between light-emitting diode (LED) chips and quantum dot (QD) converters with effective heat dissipation. However, serious reflection loss occurs at the lead frame owing to the inverted bonding of LED chips. In this study, the scattering nanoparticles-induced reflection effect has been developed to enhance the optical efficiency of inverted QD-LEDs combined with the centrifugation technique. The strong back-scattered effect of boron nitride (BN) nanoparticles with a thin columnar structure is chosen for reflection enhancement according to the ray-tracing and finite different time-domain simulations. Furthermore, a centrifugation technique is introduced to control the equilibrium geometry of the BN-incorporating reflector (BNR) by changing the centrifugal speed. Results indicate that the luminous flux of inverted QD/BNR-LEDs using the optimized concave BNR structure largely increases by 82.8% compared with reference inverted QD-LEDs. The great enhancement is attributed to the light concentrated effect of the concave geometry and the strong diffusion reflection ability of BN scattering nanoparticles. Consequently, the smart design on reflection properties of inverted QD-LEDs is critical for achieving high optical performances.