摘要:

Broader contextKey challenges to the design of more efficient solid-state dye sensitized solar cells (DSSCs) include the minimization of interfacial charge recombination losses and the improvement of the spectral overlap of the absorber layer with the solar spectrum. At present there is interest in the use of inorganic nanocrystals such as quantum dots as sensitizers in DSSCs. To improve the spectral coverage of CdS sensitized nanocrystalline TiO2 based architectures, we perform selective adsorption of dye sensitizer molecules to CdS nanocrystals. Moreover we demonstrate that the intermediate CdS layer serves as a multifunctional blocking layer that is able to absorb light and can serve as a mediator in a redox cascade system, thereby minimizing charge recombination between the photogenerated electrons and holes.

ISSN:0046-225X    

DOI:10.1039/b911527g

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

Broader contextOrganic-based solar cells have the potential of offering a low cost, flexible, light-weight, clean, and quiet alternative energy sources for a variety of applications. The highest efficiency organic solar cell design is the bulk heterojunction (BHJ) architecture (∼5.6%) in which the active layer consists of a blend of electron donating (p-type) and electron accepting (n-type) materials forming an interpenetrating network of the hole and electron accepting components. The interpenetrating network formation depends strongly on the interactions between the donor and the acceptor and processing conditions. Here, we explore the effect of donor–acceptor interactions on the blended film morphology, phase separation, and device characteristics of solution processed diketopyrrolopyrrole-based BHJ solar cells. We found that unlike conjugated polymers, the degree of phase separation before and after thermal annealing of the blends can be controlled by the alkyl substituents on the fullerene acceptor. Changes in film morphology and phase separation lead to significant differences on the performance of the as cast and annealed devices.

ISSN:0046-225X    

DOI:10.1039/b912824g

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

Broader impactHigh quality ultra-thin oxide films such as zirconia are of tremendous importance in energy sciences and technologies. Controlling oxide stoichiometry and oxygen concentration in the near surface regions of ultra-thin oxide films has a significant bearing on the functional properties of the synthesized oxide film and is of great significance. In this work, we show that atomic scale control of oxygen concentration in the near surface region of complex ultra-thin oxide films is possibleviaexternally applied electric fields (∼107V/cm). Zirconia ultra-thin films grown in the presence of electric field (∼107V/cm) are shown to have significantly improved rates of oxygen incorporation compared to native oxide. Precise understanding of the microscopic processes involved in electric field assisted oxidation is provided by the atomistic models employing dynamic charge transfer between atoms. We find that lowering of activation energy barriers in the presence of electric fields is responsible for the dramatic density and stoichiometry improvements in ultra-thin oxide films. Our atomistic simulations demonstrate a pathway to athermally tune oxygen concentration in the near surface regions of complex oxides that is of great importance to contemporary problems ranging from catalysis to energy and electronic device technologies.

ISSN:0046-225X    

DOI:10.1039/b913154j

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

Broader contextRecently, there has been a significant increase in interest in renewable energy due to growing concerns about global climate change and potential fossil fuel shortages. Solar energy is a renewable alternative to conventional energy sources. In order to lower the fabrication cost of solar energy conversion devices, people have been investigating dye-sensitized solar cells (DSCs), which can be fabricated using screen printing and low cost materials. To improve device efficiency, a TiCl4treatment for nanocrystalline TiO2films has been used to increase the current generation within the film. Although many articles on this method have been published, it still remains unclear why the TiCl4treatment increases the current generation. This paper is the first attempt to clearly prove the roll the TiCl4treatment plays in increasing the current generation using a back contact dye sensitized solar cell configuration sensitized with black dye. This configuration is suitable for addressing the TiCl4treatment effect because the electron transport and electron injection are more sensitive in this configuration than in conventional DSCs sensitized with bipyridyne dyes (N3, N719). The results of our experiment suggest that the TiCl4treatment increases electron transport and electron lifetime within the nanocrystalline TiO2film.

ISSN:0046-225X    

DOI:10.1039/b909689b

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

Broader contextDirect methanol fuel cells (DMFCs) have reached a high level of development and are now almost universally referred to as the sixth-fuel-cell type. In terms of applications, they are set to function as power sources for a range of mobile applications, a situation brought about by the convenience of storage of liquid fuel. For an expansion of the applications of DMFCs, efforts are being expended to develop improved and cost-effective polymer-electrolyte membranes that would mitigate methanol cross-over from the anode to the cathode. It is desirable that these membranes comprise non-hazardous chemicals. Accordingly, this study is an attempt to realise a membrane electrolyte from natural precursors such that the process generates little toxicity to the environment. The polymer electrolyte membrane, derived from naturally abundant chitosan (CS) and hydroxy ethyl cellulose (HEC), possesses good methanol-barrier properties and exhibits high proton-conductivity, the pre-requisites required for a membrane to be used in DMFCs. Stabilised salt of phosphotungstic acid (PTA) is incorporated to the CS-HEC blend to enhance the proton conductivity of the membrane. Preferential water-sorption characteristics of the CS-HEC-PTA mixed matrix play an important role in ameliorating the DMFC performance.

ISSN:0046-225X    

DOI:10.1039/b909451b

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

Broader contextCrude fats and oils extracted from animal or vegetable sources (containing mainly triglycerides) are currently among the most important and used raw biomaterials converted into biofuels. Although this transformation can be accomplished using relatively simple chemical reactions—thermocatalytic cracking to produce diesel-like and (trans)esterification of triglycerides to yield biodiesel, they have several drawbacks mainly related to energy and water consumption. Therefore the development of more efficient catalytic processes for these transformations is one of the key factors that inhibits the definitive implementation of such fuels globally. In this article we highlight the most recent catalytic approaches used for the alcoholysis of triglycerides and the thermolysis of crude vegetable oils.

ISSN:0046-225X    

DOI:10.1039/b910806h

出版商:RSC    

年代:2009

数据来源: RSC