Influence of tin doped TiO2 nanorods on dye sensitized solar cells

The one-step hydrothermal method was used to synthesize Sn-doped TiO2 (Sn-TiO2) thin films, in which the variation in Sn content ranged from 0 to 7-wt % and, further, its influence on the performance of a dye-sensitized solar cell (DSSC) photoanode was studied. The deposited samples were analyzed by X-ray diffraction (XRD) and Raman spectroscopy, which confirmed the existence of the rutile phase of the synthesized samples with crystallite size ranges in between 20.1 to 22.3 nm. In addition, the bare and Sn-TiO2 thin films showed nanorod morphology. A reduction in the optical band gap from 2.78 to 2.62 eV was observed with increasing Sn content. The X-ray photoelectron spectroscopy (XPS) analysis confirmed Sn4+ was successfully replaced at the Ti4+ site. The 3-wt % Sn-TiO2 based DSSC showed the optimum efficiency of 4.01%, which was superior to 0.87% of bare and other doping concentrations of Sn-TiO2 based DSSCs. The present work reflects Sn-TiO2 as an advancing material with excellent capabilities, which can be used in photovoltaic energy conversion devices

Ion-by-Ion Adsorption Process and Reaction for the Synthesis of Hierarchical Manganese Tungstate (MnWO₄) Microflowers as an Energy-Efficient Electrode for Supercapacitors

For the first time, manganese tungstate (MnWO4) electrodes are successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) method. This study is mainly focused on synthesized hierarchical MnWO4 microflowers (MFs) for electrochemical supercapacitor application. The crystalline structure, morphology, presence of functional groups, stretching and bending vibration, and availability of chemical states present in the MnWO4 MFs are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy, respectively. In addition, the resultant materials undergo electrochemical analysis using a three-electrode system. As a result, the MnW-50 electrode reveals a maximum specific capacitance (Cs) and capacity (Csp) of 698 F/g and 87 mAh/g at 5 mA/cm2 with moderate energy density (ED) and power density (PD) of 19 Wh/kg and 700 W/kg, respectively. Furthermore, the aqueous hybrid device is fabricated using MnWO4 MFs as a cathode and reduced graphene oxide (rGO) as an anode material, which reveals the maximum performance of the Cs and Csp of 206 F/g and 87 mAh/g at 5 mV/s and 185 F/g and 70 mAh/g with sufficient ED, and PD of 45 Wh/kg and 1960 W/kg at 5 mA/cm2, respectively. The aforementioned results indicate the benefits and improved electrochemical efficiency of MnWO4 MFs as cathodes for hybrid supercapacitors

Influence of Tin Doped TiO2 Nanorods on Dye Sensitized Solar Cells

The one-step hydrothermal method was used to synthesize Sn-doped TiO2 (Sn-TiO2) thin films, in which the variation in Sn content ranged from 0 to 7-wt % and, further, its influence on the performance of a dye-sensitized solar cell (DSSC) photoanode was studied. The deposited samples were analyzed by X-ray diffraction (XRD) and Raman spectroscopy, which confirmed the existence of the rutile phase of the synthesized samples with crystallite size ranges in between 20.1 to 22.3 nm. In addition, the bare and Sn-TiO2 thin films showed nanorod morphology. A reduction in the optical band gap from 2.78 to 2.62 eV was observed with increasing Sn content. The X-ray photoelectron spectroscopy (XPS) analysis confirmed Sn4+ was successfully replaced at the Ti4+ site. The 3-wt % Sn-TiO2 based DSSC showed the optimum efficiency of 4.01%, which was superior to 0.87% of bare and other doping concentrations of Sn-TiO2 based DSSCs. The present work reflects Sn-TiO2 as an advancing material with excellent capabilities, which can be used in photovoltaic energy conversion devices

Square-Facet Nanobar MOF-Derived Co₃O₄@Co/N-doped CNT Core–Shell-based Nanocomposites as Cathode Materials for High-Performance Supercapacitor Studies

The binary as well as ternary nanocomposites of the square-facet nanobar Co-MOF-derived Co3O4@Co/N-CNTs (N-CNTs: nitrogen-doped carbon nanotubes) with Ag NPs and rGO have been synthesized via an easy wet chemical route, and their supercapacitor behavior was then studied. At a controlled pH of the precursor solution, square-facet nanobars of Co-MOF were first synthesized by the solvothermal method and then pyrolyzed under a controlled nitrogen atmosphere to get a core–shell system of Co3O4@Co/N-CNTs. In the second step, different compositions of Co3O4@Co/N-CNT core–shell structures were formed by an ex-situ method with Ag NPs and rGO moieties. Among several bare, binary, and ternary compositions tested in 6 M aqueous KOH electrolyte, a ternary nanocomposite having a 7.0:1.5:1.5 stoichiometric ratio of Co3O4@Co/N-CNT, Ag NPs, and rGO, respectively, reported the highest specific capacitance (3393.8 F g–1 at 5 mV s–1). The optimized nanocomposite showed the energy density, power density, and Coulombic efficiency of 74.1 W h.kg–1, 443.7 W.kg–1, and 101.3%, respectively, with excellent electrochemical stability. After testing an asymmetrical supercapacitor with a Co3O4@Co/N-CNT/Ag NPs/rGO/nickel foam cathode and an activated carbon/nickel foam anode, it showed 4.9 W h.kg–1 of energy density and 5000.0 W.kg–1 of power density

A Simple Aqueous Precursor Solution Processing of Earth-Abundant Cu₂SnS₃ Absorbers for Thin-Film Solar Cells

A simple and eco-friendly method of solution processing of Cu₂SnS₃ (CTS) absorbers using an aqueous precursor solution is presented. The precursor solution was prepared by mixing metal salts into a mixture of water and ethanol (5:1) with monoethanolamine as an additive at room temperature. Nearly carbon-free CTS films were formed by multispin coating the precursor solution and heat treating in air followed by rapid thermal annealing in S vapor atmosphere at various temperatures. Exploring the role of the annealing temperature in the phase, composition, and morphological evolution is essential for obtaining highly efficient CTS-based thin film solar cells (TFSCs). Investigations of CTS absorber layers annealed at various temperatures revealed that the annealing temperature plays an important role in further improving device properties and efficiency. A substantial improvement in device efficiency occurred only at the critical annealing temperature, which produces a compact and void-free microstructure with large grains and high crystallinity as a pure-phase absorber layer. Finally, at an annealing temperature of 600 °C, the CTS thin film exhibited structural, compositional, and microstructural isotropy by yielding a reproducible power conversion efficiency of 1.80%. Interestingly, CTS TFSCs exhibited good stability when stored in an air atmosphere without encapsulation at room temperature for 3 months, whereas the performance degraded slightly when subjected to accelerated aging at 80 °C for 100 h under normal laboratory conditions

Aqueous-Solution-Processed Cu₂ZnSn(S,Se)₄ Thin-Film Solar Cells via an Improved Successive Ion-Layer-Adsorption–Reaction Sequence

A facile improved successive ionic-layer adsorption and reaction (SILAR) sequence is described for the fabrication of Cu₂ZnSn­(S,Se)₄ (CZTSSe) thin-film solar cells (TFSCs) via the selenization of a precursor film. The precursor films were fabricated using a modified SILAR sequence to overcome compositional inhomogeneity due to different adsorptivities of the cations (Cu⁺, Sn⁴⁺, and Zn²⁺) in a single cationic bath. Rapid thermal annealing of the precursor films under S and Se vapor atmospheres led to the formation of carbon-free Cu₂ZnSnS₄ (CZTS) and CZTSSe absorber layers, respectively, with single large-grained layers. The best devices based on CZTS and CZTSSe absorber layers showed total area (∼0.30 cm²) power conversion efficiencies (PCEs) of 1.96 and 3.74%, respectively, which are notably the first-demonstrated efficiencies using a modified SILAR sequence. Detailed diode analyses of these solar cells revealed that a high shunt conductance (<i>G</i>_sh), reverse saturation current density (<i>J</i>_o), and ideality factor (<i>n</i>_d) significantly affected the PCE, open-circuit voltage (<i>V</i>_oc), and fill factor (FF), whereas the short-circuit current density (<i>J</i>_sc) was dominated by the series resistance (<i>R</i>_s) and <i>G</i>_sh. However, the diode analyses combined with the compositional and interface microstructural analyses shed light on further improvements to the device efficiency. The facile layer-by-layer growth of the kesterite CZTS-based thin films in aqueous solution provides a great promise as an environmentally benign pathway to fabricate a variety of multielement-component compounds with high compositional homogeneities