Donor-acceptor materials

Neuteboom EE, Meskers SCJ, Van Hal PA, Van Duien JKJ, Meijer EW, Janssen RAJ, Dupin H, Pourtois G, Comil J, Lazzaroni R, Bredas J-L, Beljonne D (2003) Alternating oligo(p-phenylene vinylene)-perylene bisimide copolymers synthesis, photophysics, and photovoltaic properties of a new class of donor-acceptor materials. J Am Chem Soc 125 8625... 

Table 3.1 Electrical behaviour of various donor/acceptor materials...

There is a close relationship between the morphology of active layers and performance (physical processes) of conjugated-polymer-based photovoltaic cells, which is quite important for the further performance improvement. The morphological characteristics include ordered packing of donor/acceptor materials, domain size, phase-separation stracture and interfacial diffusion structure, while physical processes include exciton diffusion, charge-transfer state separation, lifetime of charge carrier, and carrier mobility. 

Fig. 4 Chemical structures of donor, acceptor materials and buffer layer [38].

Current research aims at high efficiency PHB materials with both the high speed recording and high recording density that are required for future memory appHcations. To achieve this aim, donor—acceptor electron transfer (DA-ET) as the hole formation reaction is adopted (177). Novel PHB materials have been developed in which spectral holes can be burnt on sub- or nanosecond time scales in some D-A combinations (178). The type of hole formation can be controlled and changed between the one-photon type and the photon-gated two-photon type (179). 

When the reaction of two compounds results in a product that contains all the mass of the two compounds, the product is called an addition compound. There are several kinds. In the rest of this chapter, we will discuss addition compounds in which the molecules of the starting materials remain more or less intact and weak bonds hold two or more molecules together. We can divide them into four broad classes electron donor-acceptor complexes, complexes formed by crown ethers and similar compounds, inclusion compounds, and catenanes. 

The use of interpenetrating donor-acceptor heterojunctions, such as PPVs/C60 composites, polymer/CdS composites, and interpenetrating polymer networks, substantially improves photoconductivity, and thus the quantum efficiency, of polymer-based photo-voltaics. In these devices, an exciton is photogenerated in the active material, diffuses toward the donor-acceptor interface, and dissociates via charge transfer across the interface. The internal electric field set up by the difference between the electrode energy levels, along with the donor-acceptor morphology, controls the quantum efficiency of the PV cell (Fig. 51). 

Sapsford, K. E., Berti, L. and Medintz, I. L. (2006). Materials for fluorescence resonance energy transfer analysis Beyond traditional donor-acceptor combinations. Angew. Chem. Int. Ed. 45, 4562-4588. 

In analogy to its complexes with nitrosyl cation (as described above), benzene can form donor-acceptor adducts with a variety of metallic and non-metallic Lewis acids. These lead to materials with novel optical and electrical properties that can be tuned through substituents on the aromatic ring. 

The elimination reactions of /l-acetoxy sulfones 114 to give the donor-acceptor-substituted allenes 115 by a Julia-Lythgoe process are less conventional (Scheme 7.18) [157]. A new one-step synthesis of allene-l,3-dicarboxylates 118 from acetone derivatives 116 was developed by the use of 2-chloro-l,3-dimethylimidazolinium chloride 117 [158, 159]. This elimination of water follows also the general Scheme 7.17 if a derivative of the enol, resulting from 116, is assumed as an intermediate for an elimination step. More complex processes of starting materials 119 furnished allenyl ketones 120 in high yields [160-162]. 

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