Prickly Pear Fruit Extract: Capping Agent for the Sol–Gel Synthesis of Discrete Titanium Dioxide Nanoparticles and Sensitizer for Dye-Sensitized Solar Cell

Abstract

Plant extracts have been utilized as an ecofriendly natural reducing agent for the synthesis of nanomaterials, including metal oxides. Prickly pear (opuntia) fruit extract (PPE) was used as a reducing agent for the sol–gel synthesis of titanium dioxide nanoparticles (TiO2 NPs) and as a sensitizer for the TiO2 NPs photoanode used in dye-sensitized solar cells (DSSCs). Ultraviolet-visible and infrared spectra, X-ray diffraction patterns, and scanning electron microscopic images were confirmed in the formation of semiconducting TiO2 NPs with the predominate size of ~300 nm. The use of PPE rendered discrete TiO2 NPs, whereas the typical synthesis without PPE resulted TiO2 aggregates. TiO2 NPs had a tetragonal crystalline structure, and their grain size was varied with respect to the concentration of PPE. The size of TiO2 crystallites was found to be 20, 19, 15, and 10 nm when the volume percentage of PPE was 0.2, 0.4, 0.6, and 0.8%, respectively. TiO2 NPs obtained using PPE were coated on indium-doped tin oxide substrates and sensitized with natural dye made up of PPE and synthetic dyes, namely rose Bengal (RB) and eosin yellow (EY). The photoanode fabricated with dye-sensitized TiO2 NPs was subjected to current–voltage response studies. The maximum power-conversion efficiency, 1.4%, was recorded for photoanodes sensitized with PPE dye, which is considerably higher than that for RB (1.16%) or EY (0.8%). Overall, the above findings proved that PPE can be used as a potential reducing/capping agent and TiO2 sensitizer for DSSC applications.

Determination of the Electrical Parameters of Iodine-Doped Polymer Solar Cells at the Macro- and Nanoscale for Indoor Applications

“…Growing electrical energy consumption, as well as the demand for autonomic and automated independent power grids, has pushed scientists to investigate new ways of converting solar energy and artificial light into electricity. Furthermore, it is now becoming very important to collect electrical energy [1][2][3][4][5][6][7] using OSCs [1][2][3][4][5] located not only outdoors, but also indoors [1,2]. To improve the capability of converting light into electrical charge, and hence, implement energy harvesting phenomena, the following improvements of standard [1][2][3][4][5] and inverted [5] OSCs were proposed: preparation of photovoltaic devices on an elastic substrate [1]; printing a supercapacitor on an absorber layer for the collection of charges [2]; using gold nanograting instead of an ITO layer as an anode electrode [3]; incorporation of nanoparticles into the organic active layer for improved light absorption, charge distribution and electrical energy harvesting with the use of localized surface plasmon resonance phenomenon [4]; and using a different type of electron transport layer [5].…”