Charge carriers, optimized transport

From the results of these serial experiments, it is found that whenever the thickness of an organic layer has been adjusted, the luminance efficiency of the device has increased (as shown in Fig. 6). It is because the amount of electron-hole of the device becomes more balanced via the optimization of the hole transport layer and the electron transport layer. In addition, extending the charge carrier recombining area and using more suitable HBL material and suitable thickness of its thin film will gradually increase and improve the luminance efficiency of the device. 

Within the bulk heterojimction, the donor and acceptor domains are generally disordered in volume. For exciton dissociation and charge generation a fine nanoscale intermixing is required, whereas for the efficient transport of charge carriers percolation and a certain phase separation are needed to ensure imdisturbed transport. Hence the optimization of the nanomorphology of the photoactive blend is a key issue for improving the efficiency of the photovoltaic operation [62,66,67]. 

Note that the most powerful method of improving solubility, adding in carboxylic acids or amines in order to form soluble salts, should have quite an adverse effect on permeability, unless it reduces overall charge as for lisinopril or coincidentally produces a substrate for carrier-mediated transport (e.g. via an amino acid or dipeptide transporter). In short, structure property relationships for solubility and cell permeability, like many properties that need to be optimized in going from a hit to a clinical candidate, operate by different rules, and often go in opposite directions. 

The knowledge of the chemical nature and the transport properties of impurities is essential in any analysis of dopii procedures from the point of view of the optimization of particular properties. The energy band theory does not deal with chemical phenomena and it is of no help in such cases. There have been only a few investigations, niainly experimental, of the appearance of charge carriers as a result of the introduction of complex impurities [38]. However, no attempt has been made to deduce any general relationship. Some workers have suggested fairly complex schemes, which are applicable only to special cases [1-3]. 

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