Siva Sankar Nemala

A simple route to making counter electrode for dye sensitized solar cells (DSSCs) using sucrose as carbon precursor.

Dye sensitized solar cells (DSSCs) have attracted much attention in recent years due to low cost fabrication as compared to silicon-based and thin film solar cells. Though, platinum is an excellent catalytic material for use in preparation of counter electrodes (CEs) for DSSCs it is expensive. Alternatives to replacement of platinum (Pt) that have been examined are carbon materials, conductive polymers and hybrids. In this work, counter electrode for DSSCs was fabricated using carbon material obtained from graphitization of sucrose at high temperature. A slurry of the carbon produced from sucrose graphitization was made with polyvinylpyrrolidone (PVP) as a surfactant and a coating was obtained by doctor blading the slurry over the FTO glass substrate. The current density (Jsc) and open circuit voltage (V(OC)) of fabricated cell (area 0.25 cm(2)) was 10.28 mAc m(-2) and 0.76 V respectively. The efficiency of the cell was 4.33% which was just slightly lower than that obtained for similar cells using platinum based counter electrode.

Liquid phase high shear exfoliated graphene nanoplatelets as counter electrode material for dye-sensitized solar cells

Graphene nanoplatelets (GNPs) are prepared from natural graphite by a simple and low-cost liquid phase high shear exfoliation method. The as-prepared GNPs are used as a counter electrode (CE) material for dye-sensitized solar cells (DSSCs). To confirm the Exfoliated GNPs, structural and morphological studies are carried out using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) studies. The electrochemical behaviour of GNPs as a counter electrode material is evaluated and compared with standard Platinum (Pt) electrode using cyclic-voltammetry (CV) and electrochemical impedance spectroscopy (EIS). These studies indicated that electrocatalytic activity towards I-/I3- redox mediator exhibited by the GNPs based electrode is comparable to standard Pt counter electrodes. DSSCs are fabricated using the counter electrodes made of GNPs and the photo-conversion efficiency is found to be 6.23% under standard test conditions, which is comparable to Pt based DSSCs proving them as potential alternative materials for counter electrodes.

Green synthesis of Ag and the effect of Ag on the efficiency of TiO2 based dye sensitized solar cell

Green synthesis of silver nanoparticles (AgNPs) was carried out using the aqueous extract of Carcia papaya (commonly known as papaya) leaves as reducing and capping agent. The synthesized AgNPs colloid was mixed with titanium dioxide slurry to produce Ag:TiO2 nanocomposite. The as-synthesized AgNPs and Ag:TiO2 nanocomposite were characterized for structural, optical and morphological studies. Dye sensitized solar cells (DSSCs) were fabricated with pure TiO2 and Ag:TiO2 nanocomposite photoanodes using N719 dye and their performance was investigated. The power conversion efficiency of Ag:TiO2 nanocomposite DSSC is increased by about 33.5% when compared to the efficiency of the pure TiO2 DSSC. The electrochemical impedance spectroscopic measurements showed that Ag:TiO2 nanocomposite film effectively reduce the charge transfer resistance and also increased the lifetime of the electron.

Influence of TiCl4 precursor in hydrothermal synthesis of TiO2 nanostructures

Rutile TiO2 films were deposited on the FTO substrate by the hydrothermal process using TTIP and TiCl4 as the titania precursor. Our study manifestly exhibits the influence of TiCl4 precursor on the hydrothermal growth of the TiO2 structure. The morphology of prepared film varies from nano-cauliflower to nano-flower to nano-parallelepiped rod-like structure with the addition of TiCl4 as the precursor. When TiCl4 is introduced in the precursor HCl corresponding to four times of the Ti4+ concentration is generated as a by-product during the reaction, these additional HCl promotes the etching of the nanostructure enabling the nanostructure to unfurl. We conclude that the tailoring of the nanostructure can be performed by addition of TiCl4 in the precursor

Palladium and platinum-palladium bi-layer based counter electrode for dye-sensitized solar cells with modified photoanode

Dye sensitized solar cells (DSSCs) were fabricated with palladium (Pd) and platinum-palladium (Pt-Pd) bi-layer as counter electrodes, respectively. Effects of photoanode thickness and morphology on device performance were studied. DSSCs fabricated with Pd and Pd-Pt as counter electrode (CE) showed photo conversion efficiency of 4.30% and 6.20%, respectively as compared to Platinum (Pt) based CE which showed 6.65% efficiency. Lower device performance was explained with help of cyclic voltammetry and electrochemical impedance spectroscopy (EIS) measurements of the cells.