Electron transport optimization

M. Uchida, T. Izumizawa, T. Nakano, S. Yamaguchi, K. Tamao, and K. Furukawa, Structural optimization of 2,5-diarylsiloles as excellent electron-transporting materials for organic electroluminescent devices, Chem. Mater., 13 2680-2683 (2001). 

Later, Yang and coworkers [84] reported similar electrophosphorescent fluorene copolymers 71 and 72, where the hole-transporting carbazole units have been introduced in the polymer backbone (Chart 4.25). Optimizing the polymer structure (comonomer ratio) and the device structure (blending with electron-transporting material PBD 8), the EQE of 4.9% has been achieved. 

Finally, an interesting concept, recently advanced, is the implementation of active materials as nanotube arrays. These systems have high surface area to optimize contact between semiconductor and electrolyte, and good light trapping properties. Their inner space could also be filled with catalysts or sensitizers and/ or pn junctions to obtain charge separation and facilitate electron transport [136]. 

A battery is a transducer that converts chemical energy into electrical energy and vice versa. It contains an anode, a cathode, and an electrolyte. The anode, in the case of a lithium battery, is the source of lithium ions. The cathode is the sink for the lithium ions and is chosen to optimize a number of parameters, discussed below. The electrolyte provides for the separation of ionic transport and electronic transport, and in a perfect battery the lithium ion transport number will be unity in the electrolyte. The cell potential is determined by the difference between the chemical potential of the lithium in the anode and cathode, AG = —EF. 

Overall, the rib effects are important when examining the water and local current distributions in a fuel cell. They also clearly show that diffusion media are necessary from a transport perspective. The effect of flooding of the gas-diffusion layer and water transport is more dominant than the oxygen and electron transport. These effects all result in non-uniform reaction-rate distributions with higher current densities across from the channels. Such analysis can lead to optimized flow fields as well as... 

The design of biocatalytic electrodes for activity toward gaseous substrates, such as dioxygen or hydrogen, requires special consideration. An optimal electrode must balance transport in three different phases, namely, the gaseous phase (the source of substrate), the aqueous phase (where the product water is released and ionic transport takes place), and the solid phase (where electronic transport occurs). Whereas the selectivity of biocatalysts facilitates membraneless cells for implementation in biological systems that provide an ambient electrolyte, gas-diffusion biofuel cells require an electro-... 

It is appropriate to review the various major commercial applications of amorphous semiconductor devices and to indicate the extent to which the nsefnlness of amorphons semiconductors depends on an optimization of their electronic transport properties. 

Figure 3.5.15 gives a particularly instructive example [33, 34], It refers to Sn as anode material that even in the form of (commercial) nanopowders does not show a useful cyclability. This is in sharp contrast to the morphology shown in Figure 3.5.15. The morphology leads to optimization by improving not less than seven battery-relevant parameters (1) Sn particles are mechanically decoupled and do not suffer from pulverization upon volume change on cycling. (2) Carbon provides an efficient way of electron transport along the fiber to the tin particle. (3) Li+...

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