Single-step-fabricated disordered metasurfaces for enhanced light extraction from LEDs

Abstract

While total internal reflection (TIR) lays the foundation for many important applications, foremost fibre optics that revolutionised information technologies, it is undesirable in some other applications such as light-emitting diodes (LEDs), which are a backbone for energy-efficient light sources. In the case of LEDs, TIR prevents photons from escaping the constituent high-index materials. Advances in material science have led to good efficiencies in generating photons from electron–hole pairs, making light extraction the bottleneck of the overall efficiency of LEDs. In recent years, the extraction efficiency has been improved, using nanostructures at the semiconductor/air interface that outcouple trapped photons to the outside continuum. However, the design of geometrical features for light extraction with sizes comparable to or smaller than the optical wavelength always requires sophisticated and time-consuming fabrication, which causes a gap between lab demonstration and industrial-level applications. Inspired by lightning bugs, we propose and realise a disordered metasurface for light extraction throughout the visible spectrum, achieved with single-step fabrication. By applying such a cost-effective light extraction layer, we improve the external quantum efficiency by a factor of 1.65 for commercialised GaN LEDs, demonstrating a substantial potential for global energy-saving and sustainability.

Disordered-nanoparticle–based etalon for ultrafast humidity-responsive colorimetric sensors and anti-counterfeiting displays

“…An interparticle distance of MNPs, a key factor to determine the responsive time, is manipulated by the exchange of the ligand attached to MNPs. Moreover, the ligand exchange results in the disorders of MNPs, i.e., disordered NP system that recently gained a great amount of interest (28)(29)(30)(31)(32). The induced disorders become the origin of the highly absorbing dielectric optical properties of the MNP layer, which enables more vivid and marked coloration in reflection compared to structural coloration based on conventional Fabry-Pérot resonators.…”

Review on Metasurfaces: An Alternative Approach to Advanced Devices and Instruments

“…In addition to the aforementioned research, metasurfaces have shown significant potential in light sources. Applications such as structural light projection [111], enhanced LED light extraction [112], radiation sources of X-ray [113], vacuum ultraviolet light [114], and IR light [115,116] have been demonstrated. The versatile metasurfaces have enabled compact, multifunctional imaging systems.…”

Photoluminescence engineering with nanoantenna phosphors

“…14,15 Among the emerging applications, nanoantenna phosphors, i.e., nanoantennas combined with a phosphor, can produce directionally enhanced output. 16 Nanoantenna phosphors are complementary to the nanoantenna LEDs, [17][18][19] where the nanoantenna is attached directly to LEDs. While nanoantennas with an emitter have been a hot topic in nanophotonics, [20][21][22][23][24][25][26][27][28][29][30][31][32] the combination with practical and thick phosphors has been limited so far.…”