Long-term stability of Perovskite Solar Cells (PSCs) is one of the main issues to be solved for a forthcoming commercialization of this technology. In this work, thermosetting polyurethane-based resins (PU) are proposed as effective encapsulants for Perovskite Solar Cells to prevent degradation caused by both moisture and oxygen. Application consists in a direct dropcast of precursor mixture onto the back of the device followed by in-situ polymerization, avoiding the use of other adhesives. PU are cost effective, lightweight, thermal and light-stable materials whose mechanical, chemical and physical properties can be easily tuned by thoughtful choice of their precursor. Encapsulated PSCs show extremely good stability when stored under ambient light (maximum 1000 lux) controlled humidity (28-65%) and temperature (18-30 °C) by retaining 94% of the initial power conversion efficiency after 2500 hours (4 months) whereas control devices lose 90% of their performance after 500 hours (T80 = 37 h); once stored according to ISOS-D-1 PU-protected devices showed T80 > 1200 h.. Encapsulated devices are stable even when immersed in pure water. Throughout this paper, it is demonstrated the use of PU as promising solution processed encapsulant materials for PSC, which can be a cost-effective route for future industrialization of this technology.

Rationalization of dye uptake on titania slides for dye-sensitized solar cells by a combined chemometric and structural approach / Valentina Gianotti; Giada Favaro; Luca Bonandini; Luca Palin; Gianluca Croce; Enrico Boccaleri; Emma Artuso; Wouter Van Beek; Claudia Barolo; Marco Milanesio. -In: CHEMSUSCHEM. -ISSN 1864-ISSN -5631. -7:11(2014, pp. 3039-3052. Original Citation:Rationalization of dye uptake on titania slides for dye-sensitized solar cells by a combined chemometric and structural approach A model photosensitizer (D5) for application in Dye-sensitized Solar Cells has been studied by a combination of X-ray diffraction, theoretical calculations and spectroscopic/chemometric methods. The conformational stability and flexibility of D5 and molecular interactions between adjacent molecules was characterized to obtain the driving forces governing D5 uptake and grafting process, and to infer the most likely arrangement of the molecules on the surface of titanium oxide. A spectroscopic/chemometric approach was then used, yielding information about the correlations between three variables governing the uptake itself: D5 concentration, dispersant (chenodeoxycholic acid, CDCA) concentration and contact time. The obtained regression model shows that large uptakes can be obtained at high D5 concentrations, when CDCA is present and contact time is high, or, in absence of CDCA, only if contact time is smaller, suggesting how to optimize dye uptake and photovoltaic device preparation.

Pyridinium gemini surfactants with hexadecyl chains linked to nitrogen atoms and a tuned aliphatic spacer that bridges the two pyridinium polar heads in 2,2′‐positions have been synthesized and characterized. A multitechnique approach allowed us to study the aggregation behavior, using conductivity, surface tension, and fluorescence. Graphs of the specific conductivity (κ) versus the surfactant molar concentration (C), and graphs of the molar conductivity (Λ) versus C0.5 suggest pre‐aggregation phenomena of these amphiphiles at very low concentration. The trends of Amin as a function of the spacer length confirm the hypothesis of a conformational change of the molecule with four methylene groups as spacer owing to stacking interactions between the two pyridinium rings mediated by the counterion. Moreover, the trends of Amin and counterion binding (β) suggest that the spacer must be longer than eight carbon atoms to fold efficiently toward the micellar core. The opportunity to tune the surfactant structure and aggregation properties make those surfactants—particularly the long‐chain ones for which the DNA complexing ability was shown by means of atomic force microscopy (AFM) imaging—desirable candidates for gene‐delivery experiments.

Poly(ethylene terephthalate) (PET) fibers are widely used in various fields owing to their good physical properties and chemical resistance, but PET hydrophobicity heavily compromises its use in many applications. Wet-chemical treatments are often required to induce hydrophilicity, but these can damage the polymer matrix and produce large volumes of liquid wastes. Atmospheric-pressure glow-discharge plasma (APGDP) is an alternative and ecofriendly method to obtain similar or better results with polymeric materials, compared to wet-chemical treatments. The hydrophilic behavior of PET samples is investigated after a roll-to-roll APGDP treatment by varying the plasma gas mixture, gas fluxes, and electrode temperatures. The reactive species formed in the plasma chamber are characterized by optical emission spectroscopy. The induced surface functionalization and roughness are characterized by contact-angle measurements, atomic force microscopy, and UV/Vis absorbance of a probe dye.

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