Fig. 4: Finding meta-grid parameters for optimal transmittance of a broadband LED.
From: Nanoparticle meta-grid for enhanced light extraction from light-emitting devices
a–c Optimal transmittance and corresponding nanoparticle array parameters obtained for various heights (distances) of the NP array from the LED-chip surface. The maximal transmittance T (a) achievable for different heights h, and the corresponding optimal radius (b) and corresponding optimal gap (c). In (a), the data for T represent transmittance averaged over a spectral range of 580–700nm and over incident angles ranging between 0° and 26°, at specific h. The yellow dots represent the optimum point of transmission Tmax=96.2%, obtained at an optimal (a) height hopt=33nm; and (b) optimal NP meta-grid parameters: (b) Ropt=13nm and (c) gopt=13nm. d–e Optimizing gap and height for different values of particle radii that allow transmission within 0.5% (d) and within 1% (e) of Tmax. Note that calculations within the spectral window between 580 and 700nm were performed at a step of 1nm, and angles between 0° and 26° were taken at a step of 1°. Beyond the critical angle (~26°) light emitted from the LED-chip undergoes total-internal reflection, thus failing to escape into the epoxy lens. Here, AlGaInP (n=3.49) is the semiconductor material and epoxy (n=1.58) is the encapsulating material
