When applied on the counter electrode of a dye-sensitized solar cell, functionalized graphene sheets with oxygen-containing sites perform comparably to platinum (conversion efficiencies of 5.0 and 5.5%, respectively, at 100 mW cm−2 AM1.5G simulated light). To interpret the catalytic activity of functionalized graphene sheets toward the reduction of triiodide, we propose a new electrochemical impedance spectroscopy equivalent circuit that matches the observed spectra features to the appropriate phenomena. Using cyclic voltammetry, we also show that tuning our material by increasing the amount of oxygen-containing functional groups can improve its apparent catalytic activity. Furthermore, we demonstrate that a functionalized graphene sheet based ink can serve as a catalytic, flexible, electrically conductive counter electrode material.

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Functionalized graphene as a catalytic counter electrode in dye-sensitized solar cells.

Flexible electronics offer a wide-variety of applications such as flexible circuits, flexible displays, flexible solar cells, skin-like pressure sensors, and conformable RFID tags. Carbon nanotubes (CNTs) are a promising material for flexible electronics, both as the channel material in field-effect transistors (FETs) and as transparent electrodes, due to their high intrinsic carrier mobility, conductivity, and mechanical flexibility. In this feature article, we review the recent progress of CNTs in flexible electronics by describing both the processing and the applications of CNT-based flexible devices. To employ CNTs as the channel material in FETs, single-walled carbon nanotubes (SWNTs) are used. There are generally two methods of depositing SWNTs on flexible substrates—transferring CVD-grown SWNTs or solution-depositing SWNTs. Since CVD-grown SWNTs can be highly aligned, they often outperform solution-processed SWNT films that are typically in the form of random network. However, solution-based SWNTs can be printed at a large-scale and at low-cost, rendering them more appropriate for manufacturing. In either case, the removal of metallic SWNTs in an effective and a scalable manner is critical, which must still be developed and optimized. Nevertheless, promising results demonstrating SWNT-based flexible circuits, displays, RF-devices, and biochemical sensors have been reported by various research groups, proving insight into the exciting possibilities of SWNT-based FETs. In using carbon nanotubes as transparent electrodes (TEs), two main strategies have been implemented to fabricate highly conductive, transparent, and mechanically compliant films—superaligned films of CNTs drawn from vertically grown CNT forests using the “dry-drawing” technique and the deposition or embedding of CNTs onto flexible or stretchable substrates. The main challenge for CNT based TEs is to fabricate films that are both highly conductive and transparent. These CNT based TEs have been used in stretchable and flexible pressure, strain, and chemical and biological sensors. In addition, they have also been used as the anode and cathode in flexible light emitting diodes, solar cells, and supercapacitors. In summary, there are a number of challenges yet to overcome to optimize the processing and performance of CNT-based flexible electronics; nonetheless, CNTs remain a highly suitable candidate for various flexible electronic applications in the near future.

A review of fabrication and applications of carbon nanotube film-based flexible electronics

Dye-sensitized solar cell (DSSC) offers an efficient and easily implemented technology for future energy supply. Compared to conventional silicon solar cells, it provides comparable power conversion efficiency (PCE) at low material and manufacturing costs. DSSC materials such as titanium oxide (TiO 2 ) are inexpensive, abundant and innocuous to the environment. Since DSSC materials are less prone to contamination and processable at ambient temperature, a roll-to-roll process could be utilized to print DSSCs on the mass production line. DSSCs perform better under lower light intensities, which makes them an excellent choice for indoor applications. Due to the advancement of molecular engineering, colored and transparent thin films have been introduced to enhance the aesthetic values. Up to now, such benefits have attracted considerable research interests and commercialization effort. Here, this review examines advanced techniques and research trends of this promising technology from the perspective of device modeling, state-of-art techniques, and novel device structures.

Review on dye-sensitized solar cells (DSSCs): Advanced techniques and research trends

Electrolytes in Dye-Sensitized Solar Cells

The recent surge in the utilization of semiconductor nanostructures for solar energy conversion has led to the development of high-efficiency solar cells. Some of these recent advances are in the areas of synthesis of new semiconductor materials and the ability to tune the electronic properties through size, shape, and composition and to assemble quantum dots as hybrid assemblies. In addition, processes such as hot electron injection, multiple exciton generation (MEG), plasmonic effects, and energy-transfer-coupled electron transfer are gaining momentum to overcome the efficiency limitations of energy capture and conversion. The recent advances as well as future prospects of quantum dot solar cells discussed in this perspective provide the basis for consideration as “The Next Big Thing” in photovoltaics.

Quantum Dot Solar Cells. The Next Big Thing in Photovoltaics.

A flexible carbon counter electrode for dye-sensitized solar cells

Low temperature fabrication of efficient porous carbon counter electrode for dye-sensitized solar cells

A new kind of fibrous quantum dot sensitized solar cell has been designed and fabricated by using CdS and CdSe co-sensitized TiO(2) nanotubes on Ti wire as the photoanode and highly active Cu(2)S as the counter electrode. By optimizing the CdSe deposition time and the length of the nanotube, a power conversion efficiency of 3.18% has been obtained under AM 1.5 illumination (100 mW cm(-2)). The potential application of this kind of solar cell has also been discussed in this paper.

http://iopscience.iop.org/article/10.1088/0957-4484/21/37/375201/pdf

Fibrous CdS/CdSe quantum dot co-sensitized solar cells based on ordered TiO2 nanotube arrays

The dye-sensitized solar cell (DSC) as a low price photovoltaic technology has attracted widespread attention in recent years. During its progress to practical application, replacement of the liquid electrolytes by solid-state ones has been found to be necessary. Alternative solid-state electrolytes have thus been developed. This review deals with the recent progress of different solid-state electrolytes on DSCs. In particular, representative examples are highlighted with the results of our solid-state composite electrolytes based on addition compounds.

Optimization the solid-state electrolytes for dye-sensitized solar cells

Cu2S nanocrystal particles were in situ deposited on graphite paper to prepare nano-sulfide/carbon composite counter electrode for CdS/CdSe quantum-dot-sensitized solar cell (QDSC). By optimization of deposition time, photovoltaic conversion efficiency up to 3.08% was obtained. In the meantime, this composite counter electrode was superior to the commonly used Pt, Au and carbon counter electrodes. Electrochemical impedance spectra further confirmed that low charge transfer resistance at counter electrode/electrolyte interface was responsible for this, implied the potential application of this composite counter electrode in high-efficiency QDSC.

/pdf/low-cost-flexible-nano-sulfide-carbon-composite-counter-50iafb9tl0.pdf

Minghui Deng

Papers

A flexible carbon counter electrode for dye-sensitized solar cells

Low temperature fabrication of efficient porous carbon counter electrode for dye-sensitized solar cells

Fibrous CdS/CdSe quantum dot co-sensitized solar cells based on ordered TiO2 nanotube arrays

Optimization the solid-state electrolytes for dye-sensitized solar cells

Low-Cost Flexible Nano-Sulfide/Carbon Composite Counter Electrode for Quantum-Dot-Sensitized Solar Cell