Solution processible small overview

Very recently, several new classes of solution processible small molecule donors with favorable optical and electronic properties have been reported for use in OPV devices. When coupled with fullerene electron acceptors, such as [6,6]-phenyl-C7i-butyric acid methyl ester (PCy BM), solution processible small molecule based solar cells have achieved record PCEs over 8% for single layers devices and 10% for tandem cells. This chapter provides an overview of several important classes of solution processible small molecules used as donor materials in high performance OPV devices. For greater details on materials and devices, the reader is referred to several excellent reviews by Meerholz, Nguyen, Bauerle, Zhan, and Roncali. ... 

Fig. 35 Spray-dried extracts and pantothenate solution. Spray-dried calcium pantothenate overview (A) and detail (B), showing mainly particles that were damaged during preparation of the SEM sample either by the high vacuum of the SEM or by the heat created during the sputter coating process. Spray-dried Tussilago farfara extract prepared by a system using atomizing air to form droplets and leading to small particle sizes (C) and a magnification thereof (D).

The aim of this chapter is to elucidate the various electronic and optical processes that occur at heterojunctions between two semiconductor polymers. Most of the results presented are related to the presence of localized electronic states at heterojunctions between different polyfluorenes. These have an analog in solution systems of small molecules where they are called exciplex states. Here, we give an overview of the theories that have been developed for small-molecule solution systems (for more details see also [24] and [25]). In Section 2.1.3, we then discuss if and how these are applicable to solid-state films of blended conjugated polymers. 

The effects of molecular order on the gas transport mechanism in polymers are examined. Generally, orientation and crystallization of polymers improves the barrier properties of the material as a result of the increased packing efficiency of the polymer chains. Liquid crystal polymers (LCP) have a unique morphology with a high degree of molecular order. These relatively new materials have been found to exhibit excellent barrier properties. An overview of the solution and diffusion processes of small penetrants in oriented amorphous and semicrystalline polymers is followed by a closer examination of the transport properties of LCP s. 

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