Enhanced Directional Light Extraction from Patterned Rare‐Earth Phosphor Films

Abstract

even metallic periodic arrays [7-9] to aid the emitted light escape the bulk of the device. Phosphors are the materials most commonly used in solid-state lighting. [10] They usually consist of inorganic matrices doped with rare-earth (RE) cations. RE phosphors offer high thermal and chemical stability and are used as color-converting materials along with blue or UV light-emitting diodes (LEDs) to obtain emissions that cover different ranges of the visible spectrum. This approach has allowed the development of artificial illumination, featuring lower cost and more efficient devices, and rendering better quality lighting for the last two decades. Apart from illumination, the field of use of LED-based devices is wide, from sensors to wireless communication, passing through human-centric lighting or horticulture industry. [11] On this basis, directional and spectral control of the out-coupled light intensity are features of interest for many applications. Such

Enhanced Photoluminescence of Cesium Lead Halide Perovskites by Quasi‐3D Photonic Crystals

“…As expected, the 2D-grating does not significantly alter the decay rates with respect to the values obtained in the flat sample (τ 2 ≈ 6.1 − 6.2 ns in both cases). [11] In the case of the NCs on top of the DBR, the intrinsic decay rate τ 2 decreases to 5.9 ns, still within the experimental dispersion of 0.3 ns measured among different samples (see Figure S10 and Table S3, Supporting Information). However, a clearly faster decay rate is observed for the quasi-3D PhC.…”

“…The 2D-grating on glass substrate shows a PLE with a double peak coinciding with the RW anomalies with a twofold enhancement of PL in good agreement with previous reports. [11] Similarly, the 140 nm SU-8 layer coated DBR exhibited a PLE of 4.5 for frequencies within the photonic bandgap. This significant enhancement in the PL is originated by the thin film of SU-8 on top of the DBR which breaks the periodicity of the structure, creating a planar defect, as seen in the modified reflectance spectra in Figure 5c, leading to an enhancement at the wavelength of this specific defect state.…”

“…Second, the PL of the perovskite NCs coincides within the 650 nm resonance of the quasi-3D PhCs whose field profile is depicted in Figure 4d. Matching the PL with the resonance improves light extraction (see an estimation in the Figure S11, Supporting Information) and also modifies the angular distribution of the PL [11] as seen in Figure 6. Finally, the grating leads to the appearance of photonic modes within the photonic bandgap of the DBR.…”

“…[4] In order to harness and control the emission from the cesium lead halide (CsPbX 3 ) nanocrystals, they are often accompanied by a light managing scheme that enhances the PL [9,10] or provides emission directionality. [11] It is also possible to directly shape the perovskite NCs themselves into photonic architectures such as thin films, [12] 2D gratings, [13] microdisks, [14] nanowires, [15,16] 3D photonic crystals, [17,18] or l micro hemispheres, [19] among others. Even though this material is suitable for many optoelectronic devices, its toxicity and instability against oxidation and humidity limit their potential into potentially commercial applications.…”

Highly Versatile Upconverting Oxyfluoride-Based Nanophosphor Films

“… 44 In order to produce phosphor films, we developed nanocrystal-based pastes by mixing the nanophosphors with an organic binder. 45 , 46 Full details are provided in the Methods and Materials section. Transparent flat films were deposited over quartz substrates by blade coating and heated at different temperatures, following the steps schemed in Figure 1 b.…”