Ag plasmonic nanostructures and a novel gel electrolyte in a high efficiency TiO2/CdS solar cell

Exploration of the adsorption capability by doping Pb@ZnFe2O4 nanocomposites (NCs) for decontamination of dye from textile wastewater

In the present research article we explore the synthesis method and adsorption capability of ZnFe oxides nanocomposites by using Pb as dopant. A conventional and simple batch adsorption method is selected and optimized. Pb@ZnFe2O4 NCs were fabricated by facile method i.e. co-precipitation method and characterized by FESEM, XRD, IR, EDX. The removal of dye has monitored by UV method. An outstanding result is obtained as adsorption efficiency of 1042 mg g-1 shows more significant performance than currently available bench-mark adsorbents. The optimized parameters pH 7.1, Adsorbent Mass: 50 mg, Initial Dye Concentration: 150 mg/l and Agitation Time: 90 min results in 96.49 % removal of CR (Congo red) dye. A CCD (central composite design) is applied to evaluate the role of adsorption variables. Based on its excellent performance, cost effectiveness, facile fabrication and large surface area, the Pb@ZnFe2O4 has considerable potential for the manufacture of cost effective and efficient adsorbents for environmental applications.

Stability, Scale-up, and Performance of Quantum Dot Solar Cells with Carbonate-Treated Titanium Oxide Films

A novel yet simple approach of carbonate (CBN) treatment of TiO₂ films is performed, and quantum dot solar cells (QDSCs) with high power conversion efficiencies (PCEs), reasonably good stabilities, and good fill factors (FFs) are fabricated with TiO₂-CBN films. The ability of carbonate groups to passivate defects or oxygen vacancies of TiO₂ is confirmed from a nominally enhanced band gap, a lowered defect induced fluorescence intensity, an additional Ti-OH signal obtained after carbonate decomposition, and a more capacitive low frequency electrochemical impedance behavior achieved for TiO₂-CBN compared to untreated TiO₂. A large area QDSC of 1 cm² with a TiO₂-CBN/CdS/Au@PAA (poly(acrylic acid)) photoanode delivers an enhanced PCE of 4.32% as opposed to 3.03% achieved for its analogous cell with untreated TiO₂. Impedance analysis illustrates the role of carbonate treatment in increasing the recombination resistance at the photoanode/electrolyte interfaces and in suppressing back-electron transfer to the electrolyte, thus validating the superior PCE achieved for the cell with carbonate-treated TiO₂. QDSCs with the configuration TiO₂-CBN/CdS/Au@PAA-polysulfide/SiO₂ gel-carbon-fabric/WO_3-x and active areas of 0.2-0.3 cm² yield efficiencies in the range of 5.16 to 6.3%, and the average efficiency of the cells is 5.9%. The champion cell is characterized by the following photovoltaic parameters: J_SC (short circuit current density), 11.04 mA cm^-2; V_OC (open circuit voltage), 0.9 V; FF, 0.63; and PCE, 6.3%. Stability tests performed on this cell show that dark storage has a less deleterious effect on cell performance compared to extended illumination. In dark, the PCE of the cell dropped from 5.69 to 5.52%, and under prolonged continuous irradiance of 5 h, it decreased from 5.91 to 4.83%. A scaled-up QDSC with the same architecture of 4 cm² size showed a PCE of 1.06%, and the demonstration of the lighting of a LED accomplished using this cell exemplifies that this cell can be used for powering electronic devices that require low power.

Lead-Sulfide-Selenide Quantum Dots and Gold-Copper Alloy Nanoparticles Augment the Light-Harvesting Ability of Solar Cells

Lead-sulfide-selenide (PbSSe) quantum dots (QDs) and gold-copper (AuCu) alloy nanoparticles (NPs) were incorporated into a cadmium sulfide (CdS)/titanium oxide (TiO₂ ) photoanode for the first time to achieve enhanced conversion of solar energy into electricity. PbSSe QDs with a band gap of 1.02 eV extend the light-harvesting range of the photoanode from the visible region to the near-infrared region. The conduction band (CB) edge of the PbSSe QDs is wedged between the CBs of TiO₂ and CdS; this additional level coupled with the good electrical conductivity of the dots facilitate charge transport and collection, and a high power conversion efficiency (PCE) of 4.44 % is achieved for the champion cell with the TiO₂ /PbSSe/CdS electrode. Upon including AuCu alloy NPs in the QD-sensitized electrodes, light absorption is enhance by plasmonic and light-scattering effects and also by the injection of hot electrons to the CBs of the QDs. Comparison of the incident photon-to-current conversion efficiency enhancement factors in addition to fluorescence decay and impedance studies reveal that the PbSSe QDs and AuCu alloy NPs promote charge injection to the current collector and increase the photogenerated charges produced, which thus enables the TiO₂ /PbSSe/CdS/AuCu cell to deliver the highest PCE of 5.26 % among all the various photoanode compositions used.

Counter Electrode Impact on Quantum Dot Solar Cell Efficiencies

The counter electrode (CE), despite being as relevant as the photoanode in a quantum dot solar cell (QDSC), has hardly received the scientific attention it deserves. In this study, nine CEs (single-walled carbon nanotubes (SWCNTs), tungsten oxide (WO₃), poly(3,4-ethylenedioxythiophene) (PEDOT), copper sulfide (Cu₂S), candle soot, functionalized multiwalled carbon nanotubes (F-MWCNTs), reduced tungsten oxide (WO_3-x), carbon fabric (C-Fabric), and C-Fabric/WO_3-x) were prepared by using low-cost components and facile procedures. QDSCs were fabricated with a TiO₂/CdS film which served as a common photoanode for all CEs. The power conversion efficiencies (PCEs) were 2.02, 2.1, 2.79, 2.88, 2.95, 3.78, 3.66, 3.96, and 4.6%, respectively, and the incident photon to current conversion efficiency response was also found to complement the PCE response. Among all CEs employed here, C-Fabric/WO_3-x outperforms all the other CEs, for the synergy between C-Fabric and WO_3-x comes to the fore during cell operation. The low sheet resistance of C-Fabric and its high surface area due to the meshlike morphology enables high WO_3-x loading during electrodeposition, and the good electrocatalytic activity of WO_3-x, the very low overpotential, and its high electrical conductivity that facilitate electron transfer to the electrolyte are responsible for the superior PCE. WO₃-based electrodes have not been used until date in QDSCs; the ease of fabrication of WO₃ films and their good chemical stability and scalability also favor their application to QDSCs. Futuristic possibilities for other novel composite CEs are also discussed. We anticipate this study to be useful for a well-rounded development of high-performance QDSCs.