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Journal Article
Neves, F, Stark A, Schell N, Mendes MJ, Aguas H, Fortunato E, Martins R, Correia JB, Joyce A.  2018.  Investigation of single phase Cu2ZnSn(x)Sb(1−x)S4 compounds processed by mechanochemical synthesis, Jul. Phys. Rev. Materials. 2:075404.: American Physical Society AbstractWebsite

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T. Vicente, A, Araujo A, Mendes MJ, Nunes D, Oliveira MJ, Sanchez-Sobrado O, Ferreira MP, Aguas H, Fortunato E, Martins R.  2018.  Multifunctional cellulose-paper for light harvesting and smart sensing applications. J. Mater. Chem. C. 6:3143-3181.: The Royal Society of Chemistry AbstractWebsite

A novel generation of flexible opto-electronic smart applications is now emerging{,} incorporating photovoltaic and sensing devices driven by the desire to extend and integrate such technologies into a broad range of low cost and disposable consumer products of our everyday life and as a tool to bring together the digital and physical worlds. Several flexible polymeric materials are now under investigation to be used as mechanical supports for such applications. Among them{,} cellulose{,} the most abundant organic polymer on the Earth{,} commonly used in the form of paper{,} has attracted much research interest due to the advantages of being recyclable{,} flexible{,} lightweight{,} biocompatible and extremely low-cost{,} when compared to other materials. Cellulose substrates can be found in many forms{,} from the traditional micro-cellulose paper used for writing{,} printing and food/beverage packaging (e.g. liquid packaging cardboard){,} to the nano-cellulose paper which has distinct structural{,} optical{,} thermal and mechanical properties that can be tailored to its end use. The present article reviews the state-of-the-art related to the integration and optimization of photonic structures and light harvesting technologies on paper-based platforms{,} for applications such as Surface Enhanced Raman Scattering (SERS){,} supporting remarkable 107 signal enhancement{,} and photovoltaic solar cells reaching [similar]5% efficiency{,} for power supply in standalone applications. Such paper-supported technologies are now possible due to innovative coatings that functionalize the paper surfaces{,} together with advanced light management solutions (e.g. wave-optical light trapping structures and NIR-to-visible up-converters). These breakthroughs open the way for an innovative class of disposable opto-electronic products that can find widespread use and bring important added value to existing commercial products. By making these devices ubiquitous{,} flexible and conformable to any object or surface{,} will also allow them to become part of the core of the Internet of Things (IoT) revolution{,} which demands systems{'} mobility and self-powering functionalities to satisfy the requirements of comfort and healthcare of the users.

Araújo, A, Mendes MJ, Mateus T, Costa J, Nunes D, Fortunato E, Águas H, Martins R.  2018.  Ultra-fast plasmonic back reflectors production for light trapping in thin Si solar cells. Solar Energy. 174:786-792. AbstractWebsite

A fast method is presented to fabricate plasmonic light trapping structures in just ten minutes (>5 × faster than the present state of art), with excellent light scattering properties. The structures are composed of silver nanoparticles (Ag NPs) deposited by thermal evaporation and self-assembled using a rapid thermal annealing (RTA) system. The effect of the RTA heating rate on the NPs production reveals to be crucial to the decrease of the annealing process. The Ag NPs are integrated in thin film silicon solar cells to form a plasmonic back reflector (PBR) that causes a diffused light reflectivity in the near-infrared (600–1100 nm wavelength region). In this configuration the thicknesses of the AZO spacer/passivating layers between NPs and rear mirror, and between NPs and silicon layer, play critical roles in the near-field coupling of the reflected light towards the solar cell absorber, which is investigated in this work. The best spacer thicknesses were found to be 100 and 60 nm, respectively, for Ag NPs with preferential sizes of about 200 nm. The microcrystalline silicon (μc-Si:H) solar cells deposited on such improved PBR demonstrate an overall 11% improvement on device efficiency, corresponding to a photocurrent of 24.4 mA/cm2 and an efficiency of 6.78%, against 21.79 mA/cm2 and 6.12%, respectively, obtained on flat structures without NPs.