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Transparent nature-based luminescent solar concentrator with NIR emission and integrated thermal sensing
Publication . Correia, Sandra F. H.; P. Falcão, Bruno; Figueiredo, Gonçalo; Vaz, Bárbara M. C.; Contieri, Letícia S.; Mesquita, Leonardo M. de Souza; Almeida, Juliana; Fradinho, Joana C.; Pinto, Diana C. G. A.; Fu, Lianshe; André, Paulo S.; Ventura, Sónia P. M.; Ferreira, Rute A. S.; Sencadas, Vitor; UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; LAQV@REQUIMTE; RSC - Royal Society of Chemistry
The engineering of luminescent solar concentrators (LSCs) offers a way to turn windows into energy-generating units while maintaining transparency. Through UV/blue down-shifting materials to the red/near-infrared (NIR) spectral region, the performance of building integrated photovoltaics is maximized without compromising indoor light quality. The most efficient solutions are based on quantum dots, which raise environmental concerns. To address this, natural renewable materials, like bacteriochlorophyll (BChl) from phototrophic bacteria were used to fabricate an LSC prototype dispersed in a styrene-ethylene-butylene-styrene (SEBS) matrix. The LSCs emit in the red/NIR region with an emission quantum yield of ∼7%, demonstrating external photon efficiency and electrical device efficiency values of ∼1.0% and ∼0.04%, respectively. The thermal dependence of the BChl/SEBS emission is used to set two independent thermometric parameters based on the emission and the electrical power generated by the LSC edge-mounted photovoltaic cells with relative sensitivity values up to ∼2% °C−1, which is a remarkable performance. This prototype was scaled up for an active area of 0.1 m2, representing the first large-area LSC using nature-based red/NIR emission centers.
Multi-Eavesdropper Detection Through PHY-Aware Cell-Free AP Selection
Publication . Martins, João; Conceição, Filipe; Gomes, Marco; Silva, Vitor; Dinis, Rui; Faculdade de Ciências e Tecnologia (FCT); Institute of Electrical and Electronics Engineers (IEEE)
The ability to provide reliable data rates across several coverage areas establishes massive multiple-input multiple-output (m-MIMO) cell-free (CF) systems as a pivotal technology for future sixth-generation (6G) systems. CF networks do, however, introduce additional security and network integrity vulnerabilities. For that, to complement the traditional cryptographic algorithms, physical layer security (PLS) can be an effective strategy for acquiring essential wireless network information in order to develop authentication methods against impersonation attacks. To prevent these spoofing attacks, we propose leveraging the wireless channel and the access point selection (APS) allocation schemes as authentication mechanisms. Our approach begins with a threshold-based analysis of spectral efficiency (SE) losses across different APS schemes. We then propose an algorithm capable of estimating the number of eavesdroppers executing active attacks while identifying the targeted user equipment (UE). Finally, we test the robustness of our detection scheme by examining how SE loss and achievable secrecy SE change when a single attacker is positioned at various locations relative to the targeted UE. Results demonstrate that monitoring these parameters provides critical insights into network performance and the impact of active eavesdropping. These findings highlight the potential of integrating PLS with upper-layer authentication protocols to significantly enhance wireless network security.
Enhancing the efficiency of luminescent solar concentrators via soft colloidal lithography negative templating
Publication . Guerrero-Felix, J. G.; Correia, S. F. H.; Alexandre, M.; Gonzalez-Gomez, C. D.; Sencadas, V.; Fu, L.; Ruiz-Reina, E.; André, Paulo Sérgio B.; Moraila-Martinez, C. L.; Mendes, M. J.; Ferreira, R. A. S.; Fernandez-Rodriguez, M. A.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; Elsevier
Building-integrated photovoltaics (BIPV) offers a sustainable pathway by seamlessly incorporating PV cells into architectural elements like façades and windows. In this study, we investigate the potential of luminescent down-shifting solar concentrators in combination with a nanophotonic light-trapping scheme to improve the optical-guiding capabilities and thereby enhance the energy conversion efficiency. We propose a novel cost-effective method to fabricate the photonic structures via soft colloidal lithography negative templating of thin films of TiO2 nanoparticles, successfully scaling the production to 11x11 cm2 glass windows. Through simulations and optical-electrical characterization, we demonstrate substantial improvements in energy harvesting for different angles of solar irradiation. We found increases in power output ranging from 57% for angles of incidence below 45° to above 100% for 60° thanks to the nanostructured TiO2 nanoparticles coatings added to a bottom down-shifting layer. This shows that such integrated approach can enhance both the efficiency and aesthetic appeal of solar solutions in urban environments, advancing the design of energy-efficient, sustainable buildings. Our methodology ensures consistent solar energy capture all year-round, for the relevant range of sunlight incidence angles, while preserving the transparency and multifunctionality of building elements.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso de avaliação no âmbito do Programa Plurianual de Financiamento de Unidades de I&D (2017/2018) - Financiamento Programático
Número da atribuição
UIDP/50008/2020