Publications

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Book Chapter
Vicente, António T., Andreia Araújo, Diana Gaspar, Lídia Santos, Ana C. Marques, Manuel J. Mendes, LuÍs Pereira, Elvira Fortunato, and Rodrigo Martins. "{Optoelectronics and Bio Devices on Paper Powered by Solar Cells}." Nanostructured Solar Cells. InTech, 2017. Abstract

The employment of printing techniques as cost-effective methods to fabricate low cost, flexible, disposable and sustainable solar cells is intimately dependent on the substrate properties and the adequate electronic devices to be powered by them. Among such devices, there is currently a growing interest in the development of user-oriented and multipurpose systems for intelligent packaging or on-site medical diagnostics, which would greatly benefit from printable solar cells as their energy source for autonomous operation. This chapter first describes and analyzes different types of cellulose-based substrates for flexible and cost effective optoelectronic and bio devices to be powered by printed solar cells. Cellulose is one of the most promising platforms for green recyclable electronics and it is fully compatible with large-scale printing techniques, although some critical requirements must be addressed. Paper substrates exist in many forms. From common office paper, to packaging cardboard used in the food industry, or nanoscale engineered cellulose (e.g. bacterial cellulose). However, it is the structure and content of paper that determines its end use. Secondly, proof-of-concept of optoelectronic and bio devices pro-duced by inkjet printing are described and show the usefulness of solar cells as a power source or as a chemical reaction initiator for sensors.

Mendes, Manuel J., Olalla Sanchez-Sobrado, Sirazul Haque, Tiago Mateus, Hugo Águas, Elvira Fortunato, and Rodrigo Martins. "{Wave-optical front structures on silicon and perovskite thin-film solar cells}." Solar Cells and Light Management. Elsevier, 2020. 315-354. Abstract
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Conference Paper
Mendes, MJ, S. Morawiec, I. Crupi, F. Simone, and F. Priolo. "{Colloidal self-assembled nanosphere arrays for plasmon-enhanced light trapping in thin film silicon solar cells}." Energy Procedia. 2014. Abstract
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Mendes, MJ, E. Hernández, I. Tobías, A. Martí, and A. Luque. "{Embedment of metal nanoparticles in GaAs and Si for plasmonic absorption enhancement in intermediate band solar cells}." 25th European Photovoltaic Solar Energy Conference and Exhibition - 5th World Conference on Photovoltaic Energy Conversion. Valencia, Spain 2010. 218-222. Abstract
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Tobias, I., MJ Mendes, A. Boronat, E. Lopez, P. Garcia-Linares, I. Artacho, A. Marti, S. Silvestre, and A. Luque. "{HIT intermediate-band solar cells with self-assembled colloidal quantum dots and metal nanoparticles}." 2015 IEEE 42nd Photovoltaic Specialist Conference, PVSC 2015. 2015. Abstract
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Martí, A., E. Antolín, P. G. Linares, E. Cánovas, D. {Fuertes Marrón}, C. Tablero, M. Mendes, A. Mellor, I. Tobías, M. Y. Levy, E. Hernández, A. Luque, C. D. Farmer, C. R. Stanley, R. P. Campion, J. L. Hall, S. V. Novikov, C. T. Foxon, R. Scheer, B. Marsen, H. W. Schock, M. Picault, and C. Chaix. "{IBPOWER: Intermediate band materials and solar cells for photovoltaics with high efficiency and reduced cost}." Conference Record of the IEEE Photovoltaic Specialists Conference. 2009. Abstract
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Mendes, MJ, I. Tobías, A. Martí, and A. Luque. "{Near-field light focusing by wavelenght-sized dielectric spheroids for photovoltaic applications}." Optical Nanostructures and Advanced Materials for Photovoltaics - Concepts of Light Trapping and Photon Transport. Ed. Technical O. S. A. Digest. Vol. Renewable. Austin, Texas (USA): Optical Society of America, 2011. JThC. Abstract
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Morawiec, S., MJ Mendes, SA Filonovich, T. Mateus, S. Mirabella, H. Águas, I. Ferreira, F. Simone, E. Fortunato, R. Martins, F. Priolo, and I. Crupi. "{Photocurrent enhancement in thin a-Si: H solar cells via plasmonic light trapping}." Optics InfoBase Conference Papers. 2014. Abstract
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Journal Article
Oliveira, R. D., A. Mouquinho, P. Centeno, M. Alexandre, S. Haque, R. Martins, E. Fortunato, H. Águas, and MJ Mendes. "Colloidal lithography for photovoltaics: An attractive route for light management." Nanomaterials. 11 (2021). AbstractWebsite
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Grey, P., M. Chapa, M. Alexandre, T. Mateus, E. Fortunato, R. Martins, MJ Mendes, and L. Pereira. "Combining Soft with Hard Condensed Matter for Circular Polarized Light Sensing and Logic Operations." Advanced Optical Materials. 9 (2021). AbstractWebsite
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Centeno, Pedro, Miguel Alexandre, Filipe Neves, Elvira Fortunato, Rodrigo Martins, Hugo Águas, and Manuel J. Mendes. "Copper-Arsenic-Sulfide Thin-Films from Local Raw Materials Deposited via RF Co-Sputtering for Photovoltaics." Nanomaterials. 12 (2022). AbstractWebsite

The 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 mΩ·cm to 17.4 Ω·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.

Haque, S., M. Alexandre, MJ Mendes, H. Águas, E. Fortunato, and R. Martins. "Design of wave-optical structured substrates for ultra-thin perovskite solar cells." Applied Materials Today. 20 (2020). AbstractWebsite
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Alishah, H. M., F. P. G. Choi, U. D. Menda, C. Kahveci, M. C. Rodop, MJ Mendes, and S. Gunes. "Effect of Bathocuproine Concentration on the Photovoltaic Performance of NiOx-Based Perovskite Solar Cells." Journal of the Mexican Chemical Society. 65 (2021): 149-160. AbstractWebsite
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Menda, U. D., G. Ribeiro, D. Nunes, T. Calmeiro, H. Águas, E. Fortunato, R. Martins, and MJ Mendes. "High-performance wide bandgap perovskite solar cells fabricated in ambient high-humidity conditions." Materials Advances. 2 (2021): 6344-6355. AbstractWebsite
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Alexandre, M., H. Águas, E. Fortunato, R. Martins, and MJ Mendes. "Light management with quantum nanostructured dots-in-host semiconductors." Light: Science and Applications. 10 (2021). AbstractWebsite
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Li, K., S. Haque, A. Martins, E. Fortunato, R. Martins, MJ Mendes, and C. S. Schuster. "Light trapping in solar cells: Simple design rules to maximize absorption." Optica. 7 (2020): 1377-1384. AbstractWebsite
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"Photonic Strategies for Photovoltaics: New Advances Beyond Optics." Modern Environmental Science and Engineering. 7 (2021): 642-652. AbstractWebsite
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Haque, Sirazul, Miguel Alexandre, Clemens Baretzky, Daniele Rossi, Francesca De Rossi, António T. Vicente, Francesca Brunetti, Hugo Águas, Rute A. S. Ferreira, Elvira Fortunato, Matthias Auf der Maur, Uli Würfel, Rodrigo Martins, and Manuel J. Mendes. "Photonic-Structured Perovskite Solar Cells: Detailed Optoelectronic Analysis." ACS Photonics. 9 (2022): 2408-2421. AbstractWebsite
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Sanchez-Sobrado, O., MJ Mendes, T. Mateus, J. Costa, D. Nunes, H. Aguas, E. Fortunato, and R. Martins. "Photonic-structured TCO front contacts yielding optical and electrically enhanced thin-film solar cells." Solar Energy. 196 (2020): 92-98. AbstractWebsite
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Centeno, P., M. F. Alexandre, M. Chapa, JV Pinto, J. Deuermeier, T. Mateus, E. Fortunato, R. Martins, H. Águas, and MJ Mendes. "Self-Cleaned Photonic-Enhanced Solar Cells with Nanostructured Parylene-C." Advanced Materials Interfaces. 7 (2020). AbstractWebsite
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Boane, Jenny L. N., Pedro Centeno, Ana Mouquinho, Miguel Alexandre, Tomás Calmeiro, Elvira Fortunato, Rodrigo Martins, Manuel J. Mendes, and Hugo Águas. "Soft-Microstructured Transparent Electrodes for Photonic-Enhanced Flexible Solar Cells." Micro. 1 (2021): 215-227. AbstractWebsite

Microstructured transparent conductive oxides (TCOs) have shown great potential as photonic electrodes in photovoltaic (PV) applications, providing both optical and electrical improvements in the solar cells’ performance due to: (1) strong light trapping effects that enhance broadband light absorption in PV material and (2) the reduced sheet resistance of the front illuminated contact. This work developed a method for the fabrication and optimization of wavelength-sized indium zinc oxide (IZO) microstructures, which were soft-patterned on flexible indium tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) substrates via a simple, low-cost, versatile, and highly scalable colloidal lithography process. Using this method, the ITO-coated PET substrates patterned with IZO micro-meshes provided improved transparent electrodes endowed with strong light interaction effects—namely, a pronounced light scattering performance (diffuse transmittance up to  50%). In addition, the photonic-structured IZO mesh allowed a higher volume of TCO material in the electrode while maintaining the desired transparency, which led to a sheet resistance reduction (by  30%), thereby providing further electrical benefits due to the improvement of the contact conductance. The results reported herein pave the way for a new class of photonic transparent electrodes endowed with mechanical flexibility that offer strong potential not only as advanced front contacts for thin-film bendable solar cells but also for a much broader range of optoelectronic applications.

Pimentel, A., A. Araújo, B. J. Coelho, D. Nunes, M. J. Oliveira, MJ Mendes, H. Águas, R. Martins, and E. Fortunato. "{3D ZnO/Ag surface-enhanced Raman scattering on disposable and flexible cardboard platforms}." Materials. 10 (2017). Abstract

© 2017 by the authors. In the present study, zinc oxide (ZnO) nanorods (NRs) with a hexagonal structure have been synthesized via a hydrothermal method assisted by microwave radiation, using specialized cardboard materials as substrates. Cardboard-type substrates are cost-efficient and robust paper-based platforms that can be integrated into several opto-electronic applications for medical diagnostics, analysis and/or quality control devices. This class of substrates also enables highly-sensitive Raman molecular detection, amiable to several different operational environments and target surfaces. The structural characterization of the ZnO NR arrays has been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical measurements. The effects of the synthesis time (5-30 min) and temperature (70-130 °C) of the ZnO NR arrays decorated with silver nanoparticles (AgNPs) have been investigated in view of their application for surface-enhanced Raman scattering (SERS) molecular detection. The size and density of the ZnO NRs, as well as those of the AgNPs, are shown to play a central role in the final SERS response. A Raman enhancement factor of 7 × 105was obtained using rhodamine 6 G (RG6) as the test analyte; a ZnO NR array was produced for only 5 min at 70 °C. This condition presents higher ZnO NR and AgNP densities, thereby increasing the total number of plasmonic "hot-spots", their volume coverage and the number of analyte molecules that are subject to enhanced sensing.

Vicente, A. T., PJ Wojcik, MJ Mendes, H. Águas, E. Fortunato, and R. Martins. "{A statistics modeling approach for the optimization of thin film photovoltaic devices}." Solar Energy. 144 (2017). Abstract

© 2017 The growing interest in exploring thin film technologies to produce low cost devices such as n-i-p silicon solar cells, with outstanding performances and capability to address the highly relevant energy market, turns the optimization of their fabrication process a key area of development. The usual one-dimensional analysis of the involved parameters makes it difficult and time consuming to find the optimal set of conditions. To overcome these difficulties, the combination of experimental design and statistical analysis provides the tools to explore in a multidimensional fashion the interactions between fabrication parameters and expected experimental outputs. Design of Experiment and Multivariate Analysis are demonstrated here for the optimization of: (1) the low temperature deposition (150 °C) of high quality intrinsic amorphous silicon (i-a-Si:H); and (2) the matching of the n-, i-, and p-silicon layers thickness to maximize the efficiency of thin film solar cells. The multiple regression method applied, validated through analysis of variance and evaluated against exact numerical simulations, is shown to predict the overall intrinsic layer properties and the devices performance. The results confirm that experimental design and statistical data analysis are effective approaches to improve, within a minimum time frame and high certainty, the properties of silicon thin films, and subsequently the layer structure of solar cells.

Gaspar, D., AC Pimentel, MJ Mendes, T. Mateus, BP Falcão, JP Leitão, J. Soares, A. Araújo, A. Vicente, SA Filonovich, H. Águas, R. Martins, and I. Ferreira. "{Ag and Sn Nanoparticles to Enhance the Near-Infrared Absorbance of a-Si:H Thin Films}." Plasmonics. 9 (2014): 1015-1023. AbstractWebsite
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