Perylene-based dyes

Scheme 9 Synthesis of copolymers of fluorene and perylene-based dyes...

In other copolymers the lower-energy unit acts as a trap so that the emission comes solely from it, rather than from an excited state spread along the chain, as in the above examples. Thus Mullen and coworkers [123] have prepared copolymers of fluorene containing low (1-5 mol %) perylene-based dye chromophores in which the emission comes solely from the dye units due to a combination of efficient Forster energy transfer from the fluorene units and charge trapping on the dyes. By varying the nature of the incorporated chromophore they were able to tune the emission color across the whole visible spectrum. 

Such exciton trapping has been exploited by Mullen and coworkers, who prepared copolymers of dioctylfluorene- and perylene-based dyes (1-5 mol%) by Yamamoto copolymerisation (Scheme 55) [222-224]. These materials were designed so that by efficient FOrster energy transfer from the fluorene to the dye units, efficient emission across the whole visible spectrum could be obtained. Perylene dyes were chosen as the chromophores due to their high solid-state PL quantum yields, and their excellent thermal and photochemical stability. 

Settels V, Liu W, Pflaum J, Fink RF, Engels B (2012) Comparison of the electronic structure of different perylene-based dye-aggregates. J Comput Chem 33 1544... 

In order to avoid these limitations, there is a need for alternative electrolytes which work in both n-type and p-type systems. One such class of species is the cobalt polypyridyl complexes such as Co tris(4,4"-di-ferf-butyl-2,2"-dipyridyl) perchlorate.Gibson et al. employed this redox couple in a NiO-based p-type device in conjunction with two perylene-based dyes, PI and PINDI (Figure 3.74). ... 

Benzidine-based dyes Benzo Azurine G Benzo(a)fluoranthene Benzo(b)fluoranthene Benzo(j)fluoranthene Benzo(k)fluoranthene Benzo(g,h,i)perylene Benzopurpurine 4B Benzo(a)pyrene Benzo(c) pyrene Benzo(e) pyrene Benzosulphonazole Benzothiazole Benzoyl peroxide Benzyl chloride Beryllium... 

Luo J, Xu M, Li R et al (2014) Af-Annulated perylene as an efBcient electron donor for porph3rtin-based dyes enhanced light-harvesting abihty and high-efBciency Co(ll/lII)-based dye-sensitized solar cells. J Am Chem Soc 136(l) 265-272... 

A comparison of perylene patents and review articles over the last twenty years clearly indicates the importance and potential for perylene-based pigments, dyestuffs and their derivatives in non-traditional applications such as electrophotographic photoconductors, laser dyes, and fluorescent probes . ... 

In this review, we restrict ourselves to metal-mediated assemblies of functional 7T-systems, which absorb light in the visible region (i.e. A. > 400 nm). Thus, materials whose color arises from metal ions or metal-ligand charge transfer (MLCT) are not included here. Self-assembhes derived from free base porphyrins, metalloporphyrins and perylene bisimide dyes have shown promising applications in artificial LH systems. Therefore, some fundamental properties of a few representative chromophores, namely meso-tetraphenylporphyrin (TPP), zinc tetraphenylporphyrin (ZnTPP), tetra-phenoxy-substituted perylene bisimide (PPBI) and bay area imsubstituted perylene bisimide (PBI), are briefly summarized herein. These properties are essential for the understanding of the photophysical and photochemical behavior of assemblies derived from such dyes. 

The same perylene bisimide scaffold was used to construct multichro-mophoric squares 8, which contain 16 additional antenna dye imits tethered to the tetrameric perylene-based square (Fig. 2) [48- 50]. Such metaUo-supramolecular architectures are reminiscent of the cyclic dye assemblies of light harvesting bacteria, where energy transfer from outer antenna dyes to the central reaction center is essential for efficient capture of solar light. In-... 

Seki, T., Yagai, S., Karatsu, T, and Kitamura, A. (2008) Formation of supramolecular polymers and discrete dimers of perylene bisimide dyes based on melamine-cyanurates hydrogen-bonding interactions. The Journal of Organic Chemistry, 73,3328-3335. 

Fink RF et al (2008) Exciton trapping in pi-conjugated materials a quantum-chemisfiy-based protocol applied to perylene bisimide dye aggregates. J Am Chem Soc 130 12858... 

The aim of this chapter is to give a state-of-the-art report on the plastic solar cells based on conjugated polymers. Results from other organic solar cells like pristine fullerene cells [7, 8], dye-sensitized liquid electrolyte [9], or solid state polymer electrolyte cells [10], pure dye cells [11, 12], or small molecule cells [13], mostly based on heterojunctions between phthaocyanines and perylenes [14], will not be discussed. Extensive literature exists on the fabrication of solar cells based on small molecular dyes with donor-acceptor systems (see for example [2, 3] and references therein). 

Owing to experimental difficulties, knowledge of aggregation effects in alkaline dithionite solutions of leuco vat dyes is sporadic [20,21]. Investigations based on absorption spectra have shown that, depending on concentration and temperature, planar polycyclic molecules such as the violanthrone derivatives Cl Vat Blues 19, 20 and 22 and the perylene tetracarboxydiimide derivatives Cl Vat Reds 23 and 32 are mainly present as monomers or dimers in leuco vat solutions. Violanthrones that do not have a coplanar structure because of the presence of... 

Most pigments derived from vat dyes are structurally based on anthraquinone derivatives such as indanthrone, flavanthrone, pyranthrone, or dibromoan-thanthrone. There are other polycyclic pigments which may be used directly in the form in which they are manufactured. This includes derivatives of naphthalene and perylene tetracarboxylic acid, dioxazine (Carbazole Violet), and tetrachloro-thioindigo. Quinacridone pigments, which were first introduced in 1958, and recently DPP pigments have been added to the series. 

Quite differently, Pleux et al. tested a series of three different organic dyads comprising a perylene monoimide (PMI) dye linked to a naphthalene diimide (NDI) or C60 for application in NiO-based DSSCs (Fig. 18.7) [117]. They corroborated a cascade electron flow from the valance band of NiO to PMI and, finally, to C60. Transient absorption measurements in the nanosecond time regime revealed that the presence of C60 extends the charge-separated state lifetime compared to just PMI. This fact enhanced the device efficiencies up to values of 0.04 and 0.06% when CoII/m and P/Ij electrolytes were utilized, respectively. More striking than the efficiencies is the remarkable incident photon-to-current efficiency spectrum, which features values of around 57% associated to photocurrent densities of 1.88 mA/cm2. 

Fig. 11 One-dimensional electron density projection along the c-axis for a perylene dye intercalated in an Mg/Al LDH and a structural model based on this data. Reprinted with permission from [150]. Copyright Wiley...

It is the purpose of this chapter to introduce photoinduced charge transfer phenomena in bulk heterojunction composites, i.e., blends of conjugated polymers and fullerenes. Phenomena found in other organic solar cells such as pristine fullerene cells [11,12], dye sensitised liquid electrolyte [13] or solid state polymer electrolyte cells [14], pure dye cells [15,16] or small molecule cells [17], mostly based on heterojunctions between phthalocyanines and perylenes [18] or other bilayer systems will not be discussed here, but in the corresponding chapters of this book. 

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