Plasmonic and Dielectric Metasurfaces for Solid State Lighting

Abstract

The coupling of layers of light emitting materials to nanostructured surfaces and metasurfaces provides an unique opportunity to tailor the emission, and opens new venues for the design of phosphors in solid-state-lighting. A significant enhancement of the photoluminescence, both spectrally and spatially, have been demonstrated in recent year using metallic metasurfaces.[1] In contrast, the effect of optical absorption by metals on the conversion efficiency is less studied. Here, we investigate the conversion efficiencies for emitter layers deposited on metasurfaces consisting of the periodic arrays of plasmonic and dielectric nanoparticles using an integrating sphere. [2]Total photoluminescence intensity measured in the integrating sphere (see Figure (a)) is larger for the emitting layer on the silver (Ag) nanoparticle array than the same layer on the titanium dioxide (TiO2) array and on unpatterned flat substrate, manifesting a larger pump or absorption enhancement for the Ag nanoparticle array. The conversion efficiencies are 0.95 and 0.38 for the TiO2 and Ag arrays, respectively (Figure (b)). The excitation wavelength of λ = 532 nm is well below the bandgap of TiO2 and the nanoparticles are virtually transparent, which leads to a conversion efficiency of almost one. For the Ag array, the conversion efficiency is lower due to the intrinsic losses of Ag. The results show that absorption at the excitation wavelengths by the emitter has a critical impact on the conversion efficiency.The evaluation technique used in this work to quantify the optical absorption by the array, leads to a working recipe to design resonant systems that can be exploited in solid-state-lighting applications.[1] G. Lozano et al., Light: Sci. Appl. 2 (2013) e66[2] S. Murai et al., ECS J. Solid State Sci. Technol. 9 (2020) 011614 Figure 1