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Nanocrystalline TiO 2 and reduced graphene oxide (rGO) materials have been synthesized by a simple and low-cost microwave-assisted hydrothermal method and applied in dye-sensitized solar cells (DSSCs) as photoactive and metal-free counter electrodes, respectively. Different TiO 2 nanocrystalline materials have been synthesized via the acid hydrolysis sol–gel method, followed by microwave hydrothermal treatment at 210 °C and 300 psi and at different microwave irradiation times (20, 30, 45, and 60 min) instead of the usual hydrothermal time of 12 h. The properties of the produced mesoporous nanocrystalline TiO 2 are investigated in terms of their morphology, crystal structure, optical properties, and surface area behavior using relevant characterization techniques. Maximum specific surface area values ( S BET ) of 97.77 and 100.7 m 2 g –1 are measured for TiO 2 , with the average crystallite sizes of 18.6 and 17.5 nm, at microwave irradiation times of 30 and 45 min, respectively. Different rGO samples have been prepared by the modified Hummers method, followed by microwave-assisted reduction at a temperature of 200 °C and pressure of 300 psi at different microwave irradiation times (3, 17, and 25 min). The physicochemical properties of the different rGO samples in terms of morphology, crystallization, and optical properties are characterized by TEM, XRD, and Raman spectroscopic analysis. The current density J sc of the fabricated DSSCs based on TiO 2 as the photoelectrode and rGO as the counter electrode compared with DSSCs based on Pt as the counter electrode is found to be 11.25 and 9.28 mA cm –2 , respectively. Although the overall power efficiency of the fabricated DSSCs based on rGO as the counter electrode is lower than that based on the Pt electrode, the former still exhibits promising prospects for replacing Pt with low-cost metal-free carbon-based DSSCs.

Eutectic molten salts are the most studied medium-high temperature thermal energy storage material due to their potential use in concentrated solar power plants. The aim of this work is to investigate the effect of using reduced graphene oxide (RGO) and graphene quantum dots (GQDs) on the thermal properties of eutectic molten salts. A binary nitrate eutectic mixture of NaNO 3 and KNO 3 was selected as a base material (BM) for nitrate/carbon-derivative composites. RGO and GQDs were individually mixed with the BM with different fractions ranged from 0.1 to 1.5 wt %. The results showed that RGO enhanced the thermal conductivity, heat of fusion, and total thermal energy storage capacity by 52.10%, 44.48%, and 10.44%, respectively. GQDs slightly improved the specific heat capacity for both solid and liquid phases by 2.53% and 3.13%, respectively. In addition, GQDs promoted the heat of fusion by 31.72% and raised the total TES capacity by 12.26%.

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In this work, different locally fabricated adhesive materials were examined to be used as an encapsulant for producing of photovoltaic modules. All the selected samples were characterized by FT-IR spectroscopy, TG instrument, UV-VIS spectrophotometer and electrical resistance meter. In addition, all the samples under investigation were examined by aging tests according to IEC standards for testing their stability and durability. The polymethacrylate material with UV stabilizer can be considered as an excellent commercial candidate for photovoltaic module encapsulant due to its high optical transmission, good adhesive strength with the glass, high photo-stability, high thermal stability and high electrical insulation (electrical resistance).