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- Copper-Arsenic-Sulfide Thin-Films from Local Raw Materials Deposited via RF Co-Sputtering for PhotovoltaicsPublication . Centeno, Pedro; Alexandre, Miguel; Neves, Filipe; Fortunato, Elvira; Martins, Rodrigo; Águas, Hugo; Mendes, Manuel JoaoABSTRACT: he inexorable increase of energy demand and the efficiency bottleneck of monocrystalline silicon solar cell technology is promoting the research and development of alternative photovoltaic materials. Copper-arsenic-sulfide (CAS) compounds are still rather unexplored in the literature, yet they have been regarded as promising candidates for use as p-type absorber in solar cells, owing to their broad raw material availability, suitable bandgap and high absorption coefficient. Here, a comprehensive study is presented on the structural and optoelectronic properties of CAS thin-films deposited via radio-frequency magnetron co-sputtering, using a commercial Cu target together with a Cu-As-S target with material obtained from local resources, specifically from mines in the Portuguese region of the Iberian Pyrite Belt. Raman and X-ray diffraction analysis confirm that the use of two targets results in films with pronounced stoichiometry gradients, suggesting a transition from amorphous CAS compounds to crystalline djurleite (Cu31S16), with the increasing proximity to the Cu target. Resistivity values from 4.7 m ohm center dot cm to 17.4 ohm center dot cm are obtained, being the lowest resistive films, those with pronounced sub-bandgap free-carrier absorption. The bandgap values range from 2.20 to 2.65 eV, indicating promising application as wide-bandgap semiconductors in third-generation (e.g., multi-junction) photovoltaic devices.
- Avaliação de efeitos de nanopartículas de TI02 e nanoDiamante em organismos aquáticosPublication . Diniz, M. S.; Lourenço, Joana; Crocco, Hellena; Peres, Isabel; Castro, Luísa; Ferreira, Isabel; Barquinha, Pedro; Silva, Luís; Mendonça, E.; Picado, Ana; Fortunato, Elvira
- Bioacumulação e efeitos da exposição a nanopartículas de TiO2 em Corbicula flumineaPublication . Lourenço, Joana; Diniz, M. S.; Peres, Isabel; Castro, Luísa; Ferreira, Isabel; Barquinha, Pedro; Fortunato, Elvira; Picado, Ana
- Prediction of sunlight-driven CO2 conversion: producing methane from photovoltaics, and full system design for single-house applicationPublication . Vieira, F.; Sarmento, B.; Machado, Ana; Facão, Jorge; Carvalho, Maria João; Mendes, Manuel Joao; Fortunato, Elvira; Martins, RodrigoABSTRACT: CO2 capture and utilization (CCU) technologies are being immensely researched as means to close the anthropogenic carbon cycle. One approach known as artificial photosynthesis uses solar energy from photovoltaics (PV), carbon dioxide and water to generate hydrocarbon fuels, being methane (CH4) a preferential target due to the already in place infrastructures for its storage, distribution and consumption. Here, a model is developed to simulate a direct (1-step) solar methane production approach, which is studied in two scenarios: first, we compare it against a more conventional 2-step methane production route, and second, we apply it to address the energetic needs of concept buildings with usual space and domestic hot water heating requirements. The analysed 2-step process consists in the PV-powered synthesis of an intermediate fuel - syngas - followed by its conversion to CH4 via a Fischer -Tropsch (methanation) process. It was found that the 1-step route could be adequate to a domestic, small scale use, potentially providing energy for a single-family house, whilst the 2-step can be used in both small and large scale applications, from domestic to industrial uses. In terms of overall solar-to-CH4 energy efficiency, the 2-step method reaches 13.26% against the 9.18% reached by the 1-step method. Next, the application of the direct solar methane technology is analysed for domestic buildings, in different European locations, equipped with a combination of solar thermal collectors (STCs) and PV panels, in which the heating needs that cannot be fulfilled by the STCs are satisfied by the combustion of methane synthesized by the PV-powered electrolyzers. Various combinations of situations for a whole year were studied and it was found that this auxiliary system can produce, per m(2) of PV area, in the worst case scenario 23.6 g/day (0.328 kWh/day) of methane in Stockholm, and in the best case scenario 47.4 g/day (0.658 kWh/day) in Lisbon.
- Glutathione-S-transferase activity and histological changes following exposure to TIO2 nanoparticles on juvenile Carassius auratusPublication . Diniz, M. S.; Crocco, H.; Pereira, J.; Peres, Isabel; Castro, Luísa; Mendonça, E.; Ferreira, L.; Barquinha, P.; Silva, R.J.C.; Fortunato, Elvira; Picado, Ana
- Estratégias fotónicas para fotovoltaico : novos avanços para além da óticaPublication . Mendes, Manuel Joao; Sanchez-Sobrado, O.; Haque, S.; Centeno, Pedro; Alexandre, Miguel; Ribeiro, Guilherme; Boane, J.; Mateus, T.; Mouquinho, Ana; Menda, U.D.; Águas, H.; Fortunato, Elvira; Martins, RodrigoRESUMO: Estruturas fotónicas com tamanhos comparáveis aos comprimentos de onda da luz solar são as soluções preferenciais para melhorar a eficiência de dispositivos fotovoltaicos através de aprisionamento de luz. As micro-estruturas fotónicas aqui desenvolvidas operam no regime de ótica de ondas, pelo que foram construídos modelos eletromagnéticos que permitiram encontrar os parâmetros ótimos para aplicação no contacto frontal de diferentes tipos de tecnologias, nomeadamente em células de filme fino baseadas em silício ou perovskite. Desta forma, foram obtidas diferentes arquiteturas fotónicas de células, demonstrando melhoras de até 50% na eficiência relativamente a células de referência planas. Os resultados mostram que as vantagens da aplicação de estruturas fotónicas não estão só limitadas a ganhos óticos de melhora da absorção, mas também possibilitam outros benefícios importantes tais como: ganhos elétricos devido à melhora dos contactos transparentes, e melhor desempenho em condições ambientais devido a um encapsulamento avançado dos dispositivos que confere até propriedades de auto-limpeza dos mesmos.
- Ultrafast low-temperature crystallization of solar cell graded formamidinium-cesium mixed-cation lead mixed-halide perovskites using a reproducible microwave-based processPublication . Brites, Maria João; Barreiros, M. Alexandra; Corregidor, V.; Alves, L. C.; Pinto, Joana V.; Mendes, Manuel Joao; Fortunato, Elvira; Martins, Rodrigo; Mascarenhas, JoãoABSTRACT: The control of morphology and crystallinity of solution-processed perovskite thin-films for solar cells is the key for further enhancement of the devices’ power conversion efficiency and stability. Improving crystallinity and increasing grain size of perovskite films is a proven way to boost the devices’ performance and operational robustness, nevertheless this has only been achieved with high-temperature processes. Here, we present an unprecedented low-temperature (<80 °C) and ultrafast microwave (MW) annealing process to yield uniform, compact, and crystalline FA0.83Cs0.17Pb(I(1–x)Brx)3 perovskite films with full coverage and micrometer-scale grains. We demonstrate that the nominal composition FA0.83Cs0.17PbI1.8Br1.2 perovskite films annealed at 100 W MW power present the same band gap, similar morphology, and crystallinity of conventionally annealed films, with the advantage of being produced at a lower temperature (below 80 °C vs 185 °C) and during a very short period of time (∼2.5 min versus 60 min). These results open new avenues to fabricate band gap tunable perovskite films at low temperatures, which is of utmost importance for Mechanically flexible perovskite cells and monolithic perovskite based tandem cells applications.
- Ultrafast low-temperature crystallization of solar cell graded formamidinium-cesium mixed-cation lead mixed-halide perovskites using a reproducible microwave-based process [Poster]Publication . Brites, Maria João; Barreiros, M. Alexandra; Corregidor, V.; Alves, L. C.; Pinto, Joana V.; Mendes, Manuel Joao; Fortunato, Elvira; Martins, Rodrigo; Mascarenhas, João
- LocalEnergy: Local Resources for Multifunctional Tetrahedrite-based Energy: Harvesting ApplicationsPublication . Neves, Filipe; Correia, J.B.; Esperto, Luís; Mascarenhas, João; Figueira, Isabel; de Oliveira, Daniel Pipa Soares; Salgueiro, Rute; Silva, Teresa; Santos, Beatriz; Lopes, E.B.; Gonçalves, António Pereira; Centeno, Pedro; Fortunato, Elvira; Martins, Rodrigo; Águas, Hugo; Mendes, Manuel Joao
- Investigation of single phase Cu2ZnSnxSb1-xS4 compounds processed by mechanochemical synthesisPublication . Neves, Filipe; Stark, A.; Schell, N.; Mendes, Manuel Joao; Aguas, H.; Fortunato, Elvira; Martins, Rodrigo; Correia, J.B.; Joyce, AABSTRACT: The copper zinc tin sulfide (CZTS) compound is a promising candidate as an alternative absorber material for thin-film solar cells. In this study, we investigate the direct formation of Cu1.92ZnSnx(Sb1-x)S-4 compounds [CZT(A)S], with x = 1, 0.85, 0.70, and 0.50, via a mechanochemical synthesis (MCS) approach, starting from powders of the corresponding metals, zinc sulfide, and sulfur. The thermal stability of the CZT(A)S compounds was evaluated in detail by in situ synchrotron high-energy x-ray diffraction measurements up to 700 degrees C. The CZT(A)S compounds prepared via MCS revealed a sphalerite-type crystal structure with strong structural stability over the studied temperature range. The contribution of the MCS to the formation of such a structure at room temperature is analyzed in detail. Additionally, this study provides insights into the MCS of CZTS-based compounds: the possibility of a large-scale substitution of Sn by Sb and the production of single phase CZT(A)S with a Cupoor/Zn-poor composition. A slight increase in the band gap from 1.45 to 1.49-1.51 eV was observed with the incorporation of Sb, indicating that these novel compounds can be further explored for thin-film solar cells.