Graphene has a unique atom-thick two-dimensional (2D) structure, high conductivity and charge mobility, huge specific surface area, excellent mechanical, thermal and electrical properties. Thus, it has been regarded as an important component for functional materials, especially for developing a variety of catalysts. In this review, we summarize the recent advancements in synthesizing graphene based new catalysts, and their applications in organic synthesis, sensors, environmental protection and energy related systems.

Graphene based catalysts

http://nanofm.mse.gatech.edu/Papers/20150404MaterialsToday.pdf

Recent advances in dye-sensitized solar cells: from photoanodes, sensitizers and electrolytes to counter electrodes

Dye-sensitized solar cells (DSCs) present promising low-cost alternatives to the conventional silicon (Si)-based solar cells. A DSC consists of several components, the most prominent being a titanium dioxide/metal oxide-based photoanode, a dye, an electrolyte and a counter electrode. The photoexcited electrons from the dye diffuse through the TiO2 network in the photoanode and go to the counter electrode which generally consists of platinum (Pt) sputtered onto a fluorine-doped tin oxide (FTO) plate. The Pt in the counter electrode helps in the regeneration of dyes by catalysing the I− regeneration from the I3− species in the redox couple. The morphology of Pt, its surface roughness, nature of the exposed facet, etc. play a crucial role in determining the overall efficiency of a DSC device. With Pt being a costly noble metal, reasonable efforts have been made to find cheaper alternatives. The review presented below gives a succinct summary of the materials in use as counter electrodes in DSCs, with a conclusion and future prospects section.

A review on counter electrode materials in dye-sensitized solar cells

/pdf/graphene-materials-and-their-use-in-dye-sensitized-solar-20voypijt2.pdf

Graphene Materials and Their Use in Dye-Sensitized Solar Cells

The dye-sensitized solar cell (DSSC) plays a leading role in third generation photovoltaic devices. Platinum-loaded conducting glass has been widely exploited as the standard counter electrode (CE) for DSSCs. However, the high cost and the rarity of platinum limits its practical application in DSSCs. This has promoted large interest in exploring Pt-free CEs for DSSCs. Very recently, graphene, which is an atomic planar sheet of hexagonally arrayed sp2 carbon atoms, has been demonstrated to be a promising CE material for DSSCs due to its excellent conductivity and high electrocatalytic activity. This article provides a mini review of graphene-based CEs for DSSCs. Firstly, the fabrication and performance of graphene film CE in DSSCs are discussed. Secondly, DSSC counter electrodes made from graphene-based composite materials are evaluated. Finally, a brief outlook is provided on the future development of graphene-based materials as prospective counter electrodes for DSSCs.

Graphene as a counter electrode material for dye-sensitized solar cells

Composites of few layered graphene (G) and platinum (Pt) nanoparticles (NP) with different loadings of Pt were used as counter electrode (CE) in dye-sensitized solar cell (DSSC). NPs were deposited directly on to G using pulsed laser ablation method (PLD). DSSCs formed using the composite CEs show improved performance compared to conventional Pt thin film electrode (Std Pt) and unsupported Pt NPs. Composite with 27% loading of Pt shows 45% higher efficiency (η = 2.9%), greater short circuit current (Jsc = 6.67 mA cm–2), and open circuit voltage (Voc = 0.74 V) without any loss of the fill factor (FF = 58%) as compared to the cells fabricated using Std Pt electrodes. Values of η, Jsc and Voc for DSSC using Std Pt CE were 2%, 5.05 mA cm–2 and 0.68 V, respectively. Electrochemical impedance spectroscopy using I–3/I– redox couple confirm lower values of charge transfer resistance for the composite electrodes, e.g., 2.36 Ω cm2 as opposed to 7.73 Ω cm2 of Std Pt. The better catalytic activity of these composite ...

Graphene supported platinum nanoparticle counter-electrode for enhanced performance of dye-sensitized solar cells.

The development of dye sensitized solar cells (DSSCs), which have derived inspiration from photosynthesis, has opened up exciting new possibilities and paradigms for producing solar photovoltaics possibly at lower cost. The dye-sensitized solar cells with moderate power conversion (∼10%) efficiencies can be manufactured under regular lab conditions without needing clean rooms or very specialized facilities. The entire processing need not involve even a single vapour deposition step. The DSSCs can be considered to be electrochemical devices consisting of (a) a photoanode which has a thick film of a wide band gap oxide semiconductor (like TiO2), typically coated on a transparent conductive oxide (TCO) glass substrate, with TiO2 being sensitized with adsorbed dyes that absorb visible light, (b) an electrolyte that establishes the internal electrical continuity between anode and counter electrode and mainly plays the role of regenerating the dye such that the photoexcitation, electron injection and current fl...

Dye Sensitized Solar Cells: A Review

Platinum (Pt) -free counter electrodes (CEs) for dye sensitized solar cells (DSSCs) were developed using freestanding flexible single wall carbon nanotube (SWNT) films called bucky papers (BPs). BP was irradiated with microwave plasma, created using a mixture of Ar (1%) and H2 (99%) gases, for 2 h. Raman scattering measurements revealed that no significant defects were created in the SWNTs as a result of the treatment. Plasma-treated BP (P-BP) developed vertically oriented, micron sized, pillar-like structures on its surface, while its base was still a dense random mesh of SWNTs. This unique flexible film had a larger accessible surface area and better catalytic properties. The plasma treatment improved the efficiency of BP-based DSSCs from 2.44% to 4.02%, which is comparable to Pt thin film (4.08%). The P-BP based solar cell operated with an open circuit voltage of 0.73 V and a fill factor of 0.70. It also had much higher efficiencies than films of randomly oriented plasma treated SWNTs. Using electrochemical impedance spectroscopy, the charge transfer resistances of P-BP and Pt were found to be 1.46 and 1.73 Ω cm2, respectively.

Pragyensh Kumar

Papers

Graphene supported platinum nanoparticle counter-electrode for enhanced performance of dye-sensitized solar cells.

Dye Sensitized Solar Cells: A Review

Plasma modified flexible bucky paper as an efficient counter electrode in dye sensitized solar cells