• Energy Research

The most commonly known renewable energy sources include the wind, wave, hydroelectric, biomass, and solar energy. Photovoltaic cells are divided into three main categories and referred to as generations of photovoltaic cells. The first generation of photovoltaic includes the monocrystalline silicon and multicrystalline silicon based solar cells. The second generation solar cells include amorphous silicon-based thin film solar cells - cadmium telluride/cadmium sulfide (CdTe/CdS) solar cells and copper indium gallium selenide (CIGS) solar cells. In third generation solar cells, the electrolyte plays a vital role in deciding the power conversion efficiency as well as stability. Liquid electrolytes are the conventional type of electrolyte and the most widely used transport medium. Polymer electrolytes are ionic conductors prepared by the dissolution of salts in a suitable polymer. Polymer electrolytes are divided into solid polymer electrolyte (SPE), gel polymer electrolyte (GPE) and composite polymer electrolyte (CPE).

A Guar Gum-based biopolymer (GG), a characteristic non-ionic polysaccharide extracted from guar beans, is utilized in this work as a cost-effective polymer gel electrolyte towards the fabrication of dye-sensitized solar cells (DSSC). A redox electrolyte is prepared by stirring Guar Gum biopolymer with a known amount of LiI/I, 4-tert-butylpyrdine, 1-methyl-3-propylimidazolium iodide, and polyethylene glycol for 24 hrs. The polymer gel electrolyte is carefully characterized through Fourier transform infrared spectra, UV-visible spectrum, Field-emission scanning electron microscopy and Differential Scanning Calorimetry. Using this polymer gel electrolyte, dye-sensitized solar cells are fabricated by sandwiching metal-free organic MK-2 dye coated TiO photoanode and Pt counter electrode as a photocathode. The photoelectrochemical characterization of the fabricated device shows maximum power conversion efficiency of 4.96% instead of 2.13% obtained with the liquid electrolyte without Guar Gum. The electrolyte containing Guar Gum polymer gel shows ionic conductivity (?) of 1.46 S [cm] while the liquid electrolyte show 2.44 S [cm].

In the last decades, bio-derived natural materials, such as vegetable oils, polysaccharides and biomass represent a rich source of hydroxyl precursors for the synthesis of polyols which can be potentially used to synthesize "greener" polyurethane foams. Herein a bio-based precursor (obtained from succinic acid) was used as a partial replacement of conventional polyol to synthesize PU foams. A mixture of conventional and bio-based polyol in presence of catalysts, silicone surfactant and diphenylmethane di-isocyanate (MDI) was expanded in a mold and cured for two hours at room temperature. Experimental results highlighted the suitability of this bio-precursor to be used in the production of flexible PU foams. Furthermore the chemo-physical characterization of the resulting foams show an interesting improvement in thermal stability and elastic modulus with respect to the PU foams produced with conventional polyol.

Abstract: Electronic companies must continuously innovate to meet the growing demand for safety, reliability, environmental sustainability, and cost-effective designs. Recently, there has been increasing interest from researchers, industry, and government in developing eco-friendly electronic materials that dissolve completely after use, leaving behind harmless byproducts. This work presents an example of an energy storage device based on completely biodegradable and low-cost materials, created by assembling bio-based polymers with carbonaceous fillers. Polymeric materials derived from renewable resources, such as proteins, starch, and cellulose, were processed into plastic-like products with desirable structural and functional properties. Their hydrophilic nature, rapid degradation, and chemical complexity allow these materials to serve multiple functions, from structural support to barrier protection. Notably, the ability of biopolymers to bind low-molecular-weight species (e.g., water and glycerol) and inorganic conductive particles (e.g., graphite flakes, carbon nanotubes, or graphene) results in transient dielectric composites with a surface capacitance higher than that of traditional devices based on activated carbon. These materials have the potential to revolutionize applications ranging from "green" consumer electronics to bio-resorbable medical implants-opportunities that were previously limited by the absence of suitable materials. Funding: This work was supported by the project No. CZ.02.01.01/00/22_008/0004631 “Materials and technologies for sustainable development within the Jan Amos Komensky Operational Program financed by the European Union.

Strawberries are extremely perishable fruit with a short shelf life due to its high susceptibility to mechanical injury, water loss, texture deterioration and microbiological decay, that rapidly reduces its marketability. The development of innovative and green strategies able to improve quality of strawberry is a current challenge. In this work, active adsorbent pads, consisted of a cellulose layer activated with either Chitosan (CH) or Limonene and Chitosan (CH-LO) solutions, were developed in order to preserve fresh strawberries. Results show that the strawberries stored at 8 degrees C in packaging containing CH or CH-LO coated-pads are marketable 3 d longer than controls. Furthermore, the CH pads allow for a reduction in respiratory activity and the mold counts. VOCs analysis carried out by HS-SPME/GC-MS revealed 123 compounds. PCA analysis, applied to the GC-MS dataset, to highlight cluster sampling, show that after 3 and 6 d of incubation, fruit stored with CH-LO are comparable to fresh strawberries. Although further experiments are needed to improve antimicrobial efficacy of the developed active pads, these results show a promising approach to preserve quality of strawberry during refrigerated storage.

Poly-3-(9H-carbazol-9-yl)propylmethacrylate (pCMA) is synthesized as a polymer gel electrolyte and employed in the fabrication of dye-sensitized solar cells (DSSC). The pCMA was characterized by various analytical techniques to examine its structural and thermal properties. The photovoltaic and electrochemical effects of this electrolyte in DSSCs were investigated. From the results, it was found that DSSCs assembled with pCMA-PGE is an efficient electrolyte, which yields an open-circuit voltage 545 mV and current density 10 mA for a cell of area 0.25 cm(2). pCMA-PGE device shows better performance (eta = 2.2%), and it also performs as a good host polymer matrix for redox couple in the electrolyte. Graphic abstract

A new series of transparent gel polymer electrolytes are prepared by adding various weight percent of thiourea coupled with poly(ethylene oxide) for the application of dye-sensitized solar cells. Coupling of thiourea in the presence of iodine undergoes dimerization reaction to produce formamidine disulfide. Fourier Transform Infrared spectroscopy shows that the interactions of thiourea and formamidine disulfide with electronegative ether linkage of poly(ethylene oxide) results in conformational changes of gel polymer electrolytes. Electrochemical impedance spectroscopy and linear sweep voltammetry experiments reveal an increment in ionic conductivity and tri-iodide diffusion coefficient, for thiourea modified gel polymer electrolytes. Finally, the prepared electrolytes are used as a redox mediator in dye-sensitized solar cells and the photovoltaic properties were studied. Apart from transparency, the gel polymer electrolytes with thiorurea show higher photovoltaic properties compared to bare gel polymer electrolyte and a maximum photocurrent efficiency of 7.17% is achieved for gel polymer electrolyte containing 1 wt% of thiourea with a short circuit current of 11.79 mA cm-2 and open circuit voltage of 834 mV. Finally, under rear illumination, almost 90% efficiency is retained upon compared to front illumination.

Data supplemented to the conference paper. Funding This work was supported by the project No. CZ.02.01.01/00/22_008/0004631 “Materials and technologies for sustainable development within the Jan Amos Komensky Operational Program financed by the European Union.