abstract
Multifunctional light-emitting diodes (LEDs) formed by coating deep-UV-emitting (<300 nm) LED chips with downshifting phosphors are of great interest for applications in indoor farms as both antibacterial (UV radiation) and photosynthetic agent (red light). Challenges include the fabrication of high-brightness downshifting converter films with controlled thickness excited in the deep-UV spectral region. We address it by optimizing the amount of Ba2SiO4: Eu(III) red-emitting phosphor dispersed in poly (methyl) methacrylate (PMMA), yielding luminescent films with tunable thickness. Taking advantage of the intra-4f(6) transitions, the Eu(III) luminescence is used as local probe, pointing out the presence of 8 non-equivalent local sites for the lanthanides. PMMA enables the processing of flexible films and simultaneously acts as a selective filter to deep-UV radiation, controlling the amount of UV radiation for indoor farm applications. Moreover, after the dispersion in PMMA, the Eu(III)-based luminescence remains analogous to that of the isolated phosphor with an absolute emission quantum yield of 0.11 +/- 0.01, confirming that Ba2SiO4:Eu(III)/PMMA films display desirable features to be used as coatings of deep-UV emitting LEDs toward multifunctional devices for indoor farm application. (C) The Author(s) 2019. Published by ECS.
keywords
PHOTOLUMINESCENCE PROPERTIES; LUMINESCENT PROPERTIES; LOCAL-STRUCTURE; LIGHT; PHOSPHORS; DIODES; EU3+; FABRICATION; EMISSION; EFFICACY
subject category
Materials Science; Physics
authors
Bispo, AG; Lima, SAM; Carlos, LD; Ferreira, RAS; Pires, AM
our authors
Maria Rute de Amorim e Sá Ferreira André
Full professorProjects
CICECO - Aveiro Institute of Materials (UID/CTM/50011/2019)
Díodos emissores de luz (LEDs) branca, inovadores, sintonizáveis e sustentáveis (WINLEDs)
acknowledgements
The authors are thankful to the Brazilian agencies FAPESP and CNPq for the financial research support. Airton G. Bispo-Jr is particularly grateful to the Sao Paulo research Foundation (FAPESP) for the award of some scholarships (grant No. 2015/10394-1, 2016/20421-9,and 2017/21995-1). Funding was also provided by CICECO-Aveiro Institute of Materials, FCT Ref. UID/CTM/50011/2019), and WINLEDs (POCI-01-0145-FEDER-030351) financed by national funds through the FCT/MEC and co-financed by FEDER under the PT2020 Partnership through European Regional Development Fund (ERDF) in the frame of Operational Competitiveness and Internationalization Programme (POCI). Andrei Kovalevsky from CICECO-Aveiro Institute of Materials is acknowledged for help in the heat treatments, and Rosario T. Soares from Chemistry department of University of Aveiro for XRD measurements.