Design of new materials

In order to achieve device efficiency of over 5%, new active materials have to be synthesized complying with the following design rules  

1) A low bandgap to capture photons in visible and near-infrared region. 

2) Optimized LUMO and HOMO energy levels for both efficient exciton dissociation and high Vbc- 

3) A high charge carrier mobility of over 10 charge extraction and a good fill factor. 

4) Good miscibility of donor polymers with PCBM and excellent solubility in common organic solvents. 

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The scientific interest in porphyrin ligands (Fig. 5) derives in part from their ability to accommodate a large series of different elements, often in various oxidation states. On the other hand porphyrins are planar molecules with a delocalized 18 Ti-electron system and a diatropic ring current [25], which makes them interesting for the design of new materials with applications in photochemistry [25-27]. 

Computer simulations therefore have several inter-related objectives. In the long term one would hope that molecular level simulations of structure and bonding in liquid crystal systems would become sufficiently predictive so as to remove the need for costly and time-consuming synthesis of many compounds in order to optimise certain properties. In this way, predictive simulations would become a routine tool in the design of new materials. Predictive, in this sense, refers to calculations without reference to experimental results. Such calculations are said to be from first principles or ab initio. As a step toward this goal, simulations of properties at the molecular level can be used to parametrise interaction potentials for use in the study of phase behaviour and condensed phase properties such as elastic constants, viscosities, molecular diffusion and reorientational motion with maximum specificity to real systems. Another role of ab initio computer simulation lies in its interaction... 

While these features create a number of challenges in establishing fundamental insights for experiment as well as for theory and simulation, they also represent important opportunities, as they are the features by which one can control the design of new materials. 

Collet, A., Dutasta, J.-P., Lozach, B., and Canceill, J. Cyclotriveratrylenes and Cryptophanes Their Synthesis and Applications to Host-Guest Chemistry and to the Design of New Materials. 165, 103-129 (1993). 

Yaghi OM, O Keeffe M, Ockwig NW, Chae HK, Eddaoudi M, Kim J. Reticular synthesis and the design of new materials. Nature 2003 423 705-714. 

Cyclotriveratrylenes and Cryptophanes Their Synthesis and Applications to Host-Guest Chemistry and to the Design of New Materials... 

The zeolites are also known as molecular sieves because of their capacity to discriminate between molecules they find numerous uses in separation and catalytic processes. Although they appear to be solid particles to the naked eye, they are highly porous, with a typical specific surface area of about 1000 m2/g. Catalysis is discussed in Chapter 9, but the scope of that chapter does not permit detailed discussions of the various types of catalysts and the role of physisorption and chemisorption in catalysis this vignette provides a glimpse of the rationale used in the molecular design of new materials of interest in surface chemistry and how the concepts introduced in Chapter 1 and Chapter 9 fit into the larger scheme. 

These dendrimers expand the repertoire of polymers available for study. Current investigations are primarily limited to linear polymers that possess ill-defined solution structures and fewer hydroxyl groups for further modification. The introduction of biocompatible building blocks (e.g., glycerol and lactic acid) augments the favorable and already known physical properties of dendrimers. These properties are likely to facilitate the design of new materials for specific biomedical and tissue engineering applications. 

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