Su Pei Lim

In-situ electrochemically deposited polypyrrole nanoparticles incorporated reduced graphene oxide as an efficient counter electrode for platinum-free dye-sensitized solar cells

This paper reports a rapid and in-situ electrochemical polymerization method for the fabrication of polypyrrole nanoparticles incorporated reduced graphene oxide (rGO@PPy) nanocomposites on a ITO conducting glass and its application as a counter electrode for platinum-free dye-sensitized solar cell (DSSC). The scanning electron microscopic images show the uniform distribution of PPy nanoparticles with diameter ranges between 20 and 30 nm on the rGO sheets. The electrochemical studies reveal that the rGO@PPy has smaller charge transfer resistance and similar electrocatalytic activity as that of the standard Pt counter electrode for the I3−/I− redox reaction. The overall solar to electrical energy conversion efficiency of the DSSC with the rGO@PPy counter electrode is 2.21%, which is merely equal to the efficiency of DSSC with sputtered Pt counter electrode (2.19%). The excellent photovoltaic performance, rapid and simple fabrication method and low-cost of the rGO@PPy can be potentially exploited as a alternative counter electrode to the expensive Pt in DSSCs.

Enhanced photovoltaic performance of silver@titania plasmonic photoanode in dye-sensitized solar cells

In the present investigation, silver@titania (Ag@TiO2) plasmonic nanocomposite materials with different Ag content were prepared using a simple one-step chemical reduction method and used as a photoanode in high-performance dye-sensitized solar cells. Transmission electron microscopic images revealed the uniform distribution of ultra-small Ag nanoparticles with a particle size range of 2–4 nm on the TiO2 surface. The incorporation of Ag on the TiO2 surface significantly influenced the optical properties in the region of 400–500 nm because of the surface plasmon resonance effect. The dye-sensitized solar cells (DSSCs) assembled with the Ag@TiO2-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency (4.86%) compared to that of bare TiO2 (2.57%), due to the plasmonic effect of Ag. In addition, the Ag nanoparticles acted as an electron sink, which retarded the charge recombination. The influence of the Ag content on the overall efficiency was also investigated, and the optimum Ag content with TiO2 was found to be 2.5 wt%. The enhanced solar energy conversion efficiency of the Ag@TiO2 nanocomposite makes it a promising alternative to conventional photoanode-based DSSCs.

Boosting Photovoltaic Performance of Dye-Sensitized Solar Cells Using Silver Nanoparticle-Decorated N,S-Co-Doped-TiO2 Photoanode

A silver nanoparticle-decorated N,S-co-doped TiO2 nanocomposite was successfully prepared and used as an efficient photoanode in high-performance dye-sensitized solar cells (DSSCs) with N719 dye. The DSSCs assembled with the N,S-TiO2@Ag-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 8.22%, which was better than that of a DSSC photoanode composed of unmodified TiO2 (2.57%) under full sunlight illumination (100 mWcm−2, AM 1.5 G). This enhanced efficiency was mainly attributed to the reduced band gap energy, improved interfacial charge transfer, and retarded charge recombination process. The influence of the Ag content on the overall efficiency was also investigated, and the optimum Ag content with N,S-TiO2 was found to be 20 wt%. Because of the enhanced solar energy conversion efficiency of the N,S-TiO2@Ag nanocomposite, it should be considered as a potential photoanode for high-performance DSSCs.

Promotional effect of silver nanoparticles on the performance of N-doped TiO2 photoanode-based dye-sensitized solar cells

We report the first successful application of an N-TiO2–Ag nanocomposite as an efficient photoanode for highly efficient dye-sensitized solar cells (DSSC). The N-TiO2–Ag nanocomposites with different Ag contents were prepared using a simple chemical reduction method and characterized using various suitable techniques. The DSSC assembled with the N-TiO2–Ag-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 8.15% compared to the photoanode of a DSSC composed of unmodified TiO2 (2.19%) under full sunlight illumination (100 mW cm−2, AM 1.5 G). This superior DSSC performance was due to the reduced band gap energy and retarded charge recombination that resulted from the introduction of plasmonic Ag nanoparticles on the surface of N-TiO2. The influence of the Ag content on the overall efficiency was also investigated, and the optimum Ag content for N-TiO2 was found to be 10 wt%. The enhanced solar energy conversion efficiency demonstrated by the N-TiO2–Ag nanocomposite makes it a promising alternative to conventional photoanode-based DSSCs.

Facile synthesis of Au@TiO2 nanocomposite and its application as a photoanode in dye-sensitized solar cells

In the present investigation, gold-decorated TiO2 (Au@TiO2) plasmonic nanocomposite materials were successfully prepared through a simple one-step chemical reduction method without using any stabilizer or surfactant. These materials were then used as efficient photoanodes in dye-sensitized solar cells (DSSC). The prepared nanocomposite materials were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) mapping, X-ray diffraction (XRD), photoluminescence (PL) and Raman analyses. The DSSC assembled with the Au@TiO2-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 5.61%, which was higher than the unmodified TiO2 photoanode (2.55%) under full sunlight illumination (100 mW cm−2, AM 1.5 G). This enhanced efficiency is mainly attributed to the plasmonic effect, reduction in the band gap energy, improved interfacial charge transfer, and retarded charge recombination process. The influence of the Au content on the overall efficiency was also investigated, and the optimum Au content with TiO2 was found to be 2.5 wt%. The significant improvement in the solar energy conversion efficiency with the Au@TiO2-plasmonic nanocomposite showed its potential as a photoanode for high-efficiency DSSC.

Catalyst-assisted electrochemical deposition of graphene decorated polypyrrole nanoparticles film for high-performance supercapacitor

A simple catalyst-assisted electrochemical deposition technique has been implemented to control the particle size of polypyrrole in the range of 5 to 10 nm embedded on graphene sheets, in which the nanocomposite will be used as a supercapacitor electrode material. The polypyrrole/graphene nanocomposite resulting from this approach maximizes the pseudocapacitive contribution of redox-active polypyrrole and electrical double layer capacitance (EDLC) contributed by individual graphene sheets. Specific capacitance, as high as 797.6 F g−1 is obtained when 1.0 mM of FeCl3 catalyst is added to the deposition solution, which is approximately four times higher than that of polypyrrole film and 2.6 times higher than that of polypyrrole/graphene nanocomposite in the absence of catalyst. This increase is attributed to the controlled particle size of polypyrrole growth on individual graphene sheets, which prevents the overlapping of graphene sheets. This gives rise to a highly open structure, which provides an easier access of electrolyte within the matrix of the nanocomposite film. A fabricated symmetric supercapacitor device yields a specific capacitance of 463.15 F g−1 and capacitance retention of 77.7% over 10 000 charge/discharge cycles at a current density of 1 A g−1. The nanocomposite serves as a promising electrode material for supercapacitors.

MICROSTRUCTURAL CHANGES OF CARBONACEOUS MONOLITHS SYNTHESIZED VIA HYDROTHERMAL METHOD

Carbonaceous monoliths were successfully synthesized via a facile hydrothermal processing route using phenol as a carbon precursor. The x-ray diffraction (XRD) patterns revealed distinguishable (002) and (100) planes of graphite at approximately 2θ = 23° and 44°, respectively. The fourier transform infrared (FTIR) spectroscopy corresponded to the chemical bonds of graphite, which were C=C and C-H. The carbonaceous monoliths exhibited interesting morphological changes as a result of varying the type of polymer which acted as a structure directing agent, mass of polymer, mass of phenol and hydrothermal temperature before and after calcination.