Polymer donor-acceptor-type copolymer

Other thiophene-based donor-acceptor-type copolymers that have shown efficiencies of over 4.2% include poly (fluorene-dicyclopentathiophene-a/t-benzothiadiazole) (65, Figure 25), poly(carbazole-dicyclopentathiophene-aft-benzothiadiazole) 66, and poly[9,9-dialkylfluorene-a/t-(bis-thienylene)benzothiadiazole] 67-69. Some other thiophene-based polymer designs, which have attracted... 

It is also found that the position of alkyl chain has an obvious effect on the molecular weights and photovoltaic performance of the resulting polymers. Gao et al. synthesized a series of internal donor-acceptor type of copolymers 78 containing BT and four thiophenes incorporating side chains on different position as shown in Fig. 2.4B (Wang et al., 2009). 

Until recently, catalyst-transfer polycondensations were limited to the preparation of p-type 7i-conjugated polymers and block copolymers comprising relatively simple electron-rich building blocks (such as thiophene). On the other hand, well-defined conjugated donor-acceptor alternate copolymers and donor-acceptor all-conjugated block copolymers are needed for practical applications. Very recently, controlled polymerizations of a few electron-deficient monomers were also reported." ... 

The second type of nonideal models takes into account the possible formation of donor-acceptor complexes between monomers. Essentially, along with individual entry of these latter into a polymer chain, the possibility arises for their addition to this chain as a binary complex. A theoretical analysis of copolymerization in the framework of this model revealed (Korolev and Kuchanov, 1982) that the statistics of the succession of units in macromolecules is not Markovian even at fixed monomer mixture composition in a reactor. Nevertheless, an approach based on the "labeling-erasing" procedure has been developed (Kuchanov et al., 1984), enabling the calculation of any statistical characteristics of such non-Markovian copolymers. 

In Section 2.1.4, the electronic and photophysical properties of donor-acceptor or type-II heterojunctions between two semiconductor polymers were investigated. Exciplex formation was found to be a general phenomenon for type-II heterojunctions between polyfluorene copolymers. These are among the most widely used materials in polymer optoelectronics, but the presence of exciplexes had not yet been fully appreciated. This is because the exciplex population is often depopulated via efficient endothermic transfer towards the exciton, which leads to bulk exciton instead of exciplex emission. However, via time- and temperature-depen-dent photoluminescence (PL) spectroscopy the exciplex states can be identified. Employing a relationship known from small-molecule solution systems that relates the relative HOMO and LUMO levels of the molecules to the exciplex emis-... 

S.-S. Sun, et al, Design, synthesis, and characterization of a novel c-donor-nc-bridge-c-acceptor type block copolymer for optoelectronic applications. J. Polym. Sci. A Polym. Chem., 2014, 52 1149-1160. 

Because isoindigo homopolymer is a typical n-type semiconductor, [14] in order to obtain p-type isoindigo-based polymers, electron-rich groups should be introduced to increase the HOMO level of the desired polymers. The donor-acceptor interactions of electron-deficient isoindigo units and electron-rich units may enhance the interchain ti-ti stacking interactions. Selenophene-(2-4) and thiophene-containing (2-5 to 2-11) units are used to construct the copolymers (Scheme 2.2). Units 2-4—2-7 and unit 2-10 are centrosymmetric, and units 2-8, 2-9 and 2-11 are... 

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