Herein we demonstrate that the patterning of thin nanophosphor films leads to the control of the red emitted light from nanophosphors doped with Eu3+. Briefly, rare-earth (RE) phosphors are the material most used in the generation of artificial light along with UV and blue light emitting diodes (LEDs). Phosphors behave as color-converting materials, they absorb part of or the entire light emitted by the LEDs to obtain emission the visible range. Thus, the management of the extraction of the light from these photoluminescent films is a key point in order to obtain more efficient or tuned color-converting layers. To do so, photonic architectures offer alternative paths without the chemical modification of the synthesis routes and the comprising of the internal efficiency. [1,2] The use of transparent films is a requirement to carry out this approach in the scale of the hundreds of nanometers. Furthermore, RE nanoparticles not only avoid the typical multiple scattering of microsized phosphor but their use also allows the use of straightforward wet-methods for the deposition. In this talk, we show the first monolithic patterned structure based on downshifting phosphors with square arrays of nanoholes with different lattice parameters (400, 500 and 600 nm). [3] Soft-lithography is employed to transfer square array of nanocylinders from PDMS cast to nanophosphor films. As a result, the emission is enhanced at selected wavelengths and directions. In particular, a two-fold enhancement is found for the red emission at normal emission direction for the larger studied lattice parameter. Our results open a route towards the development of color-converting layers with tunable emission.

References:

[1] Geng, D., Cabello-Olmo, E., Lozano, G., & Míguez, H. (2019). Tamm plasmons directionally enhance rare-earth nanophosphor emission. ACS Photonics, 6(3), 634-641.

[2] Geng, D., Cabello-Olmo, E., Lozano, G., & Míguez, H. (2018). Photonic structuring improves the colour purity of rare-earth nanophosphors. Materials horizons, 5(4), 661-667.

[3] Cabello‐Olmo, E., Molet, P., Mihi, A., Lozano, G., & Míguez, H. (2021). Enhanced Directional Light Extraction from Patterned Rare‐Earth Phosphor Films. Advanced Optical Materials, 9(2), 2001611.