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Research Project
Institute of Nanostructures, Nanomodelling and Nanofabrication
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Publications
Células solares ultrafinas de Cu (In,Ga)Se2 : passivação de interfaces
Publication . Curado, M.A.; Cunha, J.M.V.; Alberto, H.V.; Vilão, R.C.; Simões, A.F.A.; Fernandes, P.A.; Teixeira, J.P.; Leitão, J.; Gil, J.M.; Salomé, P.M.P.
RESUMO: A comunidade de Cu(In,Ga)Se2 (CIGS) tem focado grande parte da sua investigação no estudo e melhoramento das propriedades cristalinas do CIGS.A última estratégia utilizada, que tem permitido aumentar o valor de eficiência das células solares, passa pela implementação de elementos alcalinos através de tratamentos pós-deposição (PDT). Para se atingir valores de conversão de eficiência competitivos é necessário melhorar as interfaces do CIGS. Neste estudo, focamo-nos no estudo das propriedades morfológicas, estruturais e optoelectrónicas entre o CIGS e a alumina (Al2O3), que tem o potencial de ser usada como camada passivadora frontal. Pode-se concluir que as propriedades morfológicas e estruturais não são alteradas devido à deposição do Al2O3. O Al2O3 não resiste ao banho químico usado para a deposição do CdS. O Al2O3 apresenta um valor de densidade de defeitos baixos, uma propriedade desejada destas camadas. Este estudo demonstra a potencialidade de se utilizar a Al2O3, para camadas buffer alternativas, que não usem processos químicos durante a sua deposição.
Copper-Arsenic-Sulfide Thin-Films from Local Raw Materials Deposited via RF Co-Sputtering for Photovoltaics
Publication . Centeno, Pedro; Alexandre, Miguel; Neves, Filipe; Fortunato, Elvira; Martins, Rodrigo; Águas, Hugo; Mendes, Manuel Joao
ABSTRACT: 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.
Sub-Bandgap Sensitization of Perovskite Semiconductors via Colloidal Quantum Dots Incorporation
Publication . Ribeiro, Guilherme; Ferreira, G.; Menda, U.D.; Alexandre, Miguel; Brites, Maria João; Barreiros, M. Alexandra; Jana, S.; Águas, Hugo; Martins, Rodrigo; Fernandes, P.A.; Salomé, P.M.P.; Mendes, M.J.
ABSTRACT: By taking advantage of the outstanding intrinsic optoelectronic properties of perovskite-based photovoltaic materials, together with the strong near-infrared (NIR) absorption and electronic confinement in PbS quantum dots (QDs), sub-bandgap photocurrent generation is possible, opening the way for solar cell efficiencies surpassing the classical limits. The present study shows an effective methodology for the inclusion of high densities of colloidal PbS QDs in a MAPbI3 (methylammonium lead iodide) perovskite matrix as a means to enhance the spectral window of photon absorption of the perovskite host film and allow photocurrent production below its bandgap. The QDs were introduced in the perovskite matrix in different sizes and concentrations to study the formation of quantum-confined levels within the host bandgap and the potential formation of a delocalized intermediate mini-band (IB). Pronounced sub-bandgap (in NIR) absorption was optically confirmed with the introduction of QDs in the perovskite. The consequent photocurrent generation was demonstrated via photoconductivity measurements, which indicated IB establishment in the films. Despite verifying the reduced crystallinity of the MAPbI3 matrix with a higher concentration and size of the embedded QDs, the nanostructured films showed pronounced enhancement (above 10-fold) in NIR absorption and consequent photocurrent generation at photon energies below the perovskite bandgap.
Cultural Heritage analysis using Synchrotron Radiation: case studies in Ceramics, Glasses, and Lithologic Materials
Publication . Veiga, JP; Coutinho, ML; Figueiredo, Elin; Silva, Teresa
ABSTRACT: Synchrotron radiaton is a powerful tool for non‐destructve analysis of materials in cultural
heritage research. It has revolutonized our ability to understand the compositon, structure, and
history of cultural heritage objects, leading to significant advances in fields such as archaeology, art
conservation, and materials science. Dedicated beamlines for cultural heritage research are available at synchrotron facilites around the world, such as the European Synchrotron Radiation Facility (ESRF), SOLEIL synchrotron, and ALBA synchrotron, providing specialized support and instrumentation for high‐resolution analysis of cultural heritage objects using various techniques, such as X‐ray absorption spectroscopy, X‐ray fluorescence, X‐ray diffraction, and X‐ray imaging.
Mortars from the Monastery of Santa Maria de Alcobaça, in Portugal: characteristics and functions
Publication . Carvalho, Fernanda; Lima, M.M.R.A.; Silva, Teresa; Nunes, A.; Pagará, A.; Costeira, I.; Leal, Nuno; Simão, J.; Galhano, Carlos; Veiga, JP
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
6817 - DCRRNI ID
Funding Award Number
UIDB/50025/2020