Triphenylamine dyes

One of the most popular applications of molecular rotors is the quantitative determination of solvent viscosity (for some examples, see references [18, 23-27] and Sect. 5). Viscosity refers to a bulk property, but molecular rotors change their behavior under the influence of the solvent on the molecular scale. Most commonly, the diffusivity of a fluorophore is related to bulk viscosity through the Debye-Stokes-Einstein relationship where the diffusion constant D is inversely proportional to bulk viscosity rj. Established techniques such as fluorescent recovery after photobleaching (FRAP) and fluorescence anisotropy build on the diffusivity of a fluorophore. However, the relationship between diffusivity on a molecular scale and bulk viscosity is always an approximation, because it does not consider molecular-scale effects such as size differences between fluorophore and solvent, electrostatic interactions, hydrogen bond formation, or a possible anisotropy of the environment. Nonetheless, approaches exist to resolve this conflict between bulk viscosity and apparent microviscosity at the molecular scale. Forster and Hoffmann examined some triphenylamine dyes with TICT characteristics. These dyes are characterized by radiationless relaxation from the TICT state. Forster and Hoffmann found a power-law relationship between quantum yield and solvent viscosity both analytically and experimentally [28]. For a quantitative derivation of the power-law relationship, Forster and Hoffmann define the solvent s microfriction k by applying the Debye-Stokes-Einstein diffusion model (2)... 

Triphenylamine dyes, like Methyl Violet, Crystal Violet, Malachite Green or Brilliant Green, form deeply-colored compounds which are insoluble in water with molybdophosphates. ... 

Tian H, Yang X, Chen R, Zhang R, Hagfeldt A, Sun L (2008) Effect of different dye baths and dye-structures on the performance of dye-sensitized solar cells based on triphenylamine dyes. JPhys Chem C 112 11023-11033... 

Electroluminescent phenantroline dyes containing triphenylamine and 1,3,4-oxadiazole fragments were prepared using tetrazole-oxadiazole interconversion performed in the presence of aroyl chlorides <2004TL6361>. Also, iV-tributylstannyltetrazoles treated with acetic anhydride gave oxadiazole derivatives <2002RCB357>. 

IK also claimed polymeric emitting materials comprising a polyimide, polyamideimide, polyurea, or polyazomethine with a dye component such as phthalocyanine, porphyrin, triphenylamine, oxadiazole moieties or polycarbonate with a diarylvinylene arylene skeleton or styrylamine core. 

It has been suggested in the literature that the a-amino radical is the species that initiates polymerization [210], This view is supported by our observation that, in spite of the relatively high quenching rate constant of Eosin triplet by triphenylamine (Table 5), the system Eosin-triphenylamine does not sensitize the photopolymerization of multifunctional acrylates. Thus, it is necessary that the amine contains a hydrogen at the a-carbon to be released as a proton after oxidation of the amine by the dye triplet. This deprotonation prevents the back electron transfer and forms a carbon radical that is sufficiently long-lived to be captured by the monomer. 

The theory predicts a strong dependence of photogeneration efficiencies on the field and it approaches unity at high field. The temperature sensitivity decreases with the increase in field. The theory has found satisfactory explanations in the photogeneration process in many organic disordered systems, such as PVK (Scheme la) [25], and triphenylamine doped in polycarbonate [26], Figure 4 shows an example of the field dependence of c() calculated from Eq. (22) (the solid lines) to fit the quantum efficiency data at room temperature for hole and electron generation in an amorphous material. The material consists of a sexithiophene covalently linked with a methine dye molecule (compound 1) (Scheme 2). 

Steric hindrance between phenyl substituents can effectively reduce conjugation. This is most pronounced for triphenylcarbenium ions - like the well-known triphenylmethane dyes (cf. [115]) - and triphenylamine derivatives (cf. [113]). Bridging of phenyl substituents of course alleviates this... 

Larger ir systems based on the sterically encumbered oligophenyl type give as disappointing results as in the ID series, as shown by a series [113] of triphenylamine and pyrimidine derivatives (Stadler et al., 1995, 1996c). The same holds true for simple triphenylmethane dyes, as demonstrated by extensive investigations on crystal violet [115] (Kaatz and Shelton, 1996 Morrison et al., 1996 Noordman and van Hulst, 1996) which showed that... 

Functionalized alkylsilanes, such as (CH30)3Si(CH2)3NH2, have been used mainly for attaching dye molecules such as triphenylamine [517] and azobenzene derivatives [518, 519]. The grafting of molecular dipoles at the surface of ITO anode has been found to lead to a... 

The hole-transporting layer contains highly electron-rich aromatic compounds, such as the triphenylamine derivative, /n-MDTA, 11.9, whose role is to provide the required charge transport properties (Figure 11.7). Fluorescent dyes with high quantum yields are used to... 

Nanostructured semiconducting block copolymers containing triphenylamine as hole transport moiety and perylene bisimide as dye and electron transport, have been investigated in view of applications in photovoltaic devices. The polymers show nanowire like structure which formation is driven by the crystallization of perylene bisimides via n- n stacking and since this self-assembly gives rise to domains size comparable to the exciton diffusion length, these materials offer perspectives for the implementation of organic solar cells [357]. 

MIK 11] Mikroyannidis J.A., Tsagkournos D.V., BalrajuP. et al., Synthesis and photovoltaic properties of an alternating phenylenevinylene copolymer with substituted-triphenylamine units along the backbone for bulk heterojimction and dye-sensitized solar cells . Journal of Power Sources, vol. 196, no. 4, pp. 2364-2372, 2011. 

ZHA 09a] Zhang W., Fang Z., Su M. et al., A triphenylamine-based conjugated polymer with donor-jc-acceptor architecture as organic sensitizer for dye-sensitized solar cells , Macromolecular Rapid Communications, vol. 30, no. 18, pp. 1533-1537, 2009. 

Preat J, Michaux C, Jacquemin D, Perpete EA (2009) Enhanced efficiency of organic dye-sensitized solar cells triphenylamine derivatives. J Phys Chem C 113 16821-16833... 

Fig. 14 (Top) Series of triphenylamine (TPA)-based dyes where the linker conjugation is systematically increased with vinylene and thiophene units. (L ) Electron lifetime as function of Foe for DSCs based on LO (squares) and L3 (circles) using three different L concentrations (open symbols) 10 mM, (solid symbols) 50 mM, and (half-filled squares, gray circles in squares) 250 mM in the redox electrolyte. Electrolyte 0.6 M TBAI, 0.1 M Lil, and 0.5 M A-tert-butylpyridme with different L concentrations in acetonitrile. (Right) Electron lifetimes for DSCs based on LO (squares) and L3 (circles) at Foe = 0.5 V as a function of L concentration. Reproduced with permission [155]...

Marinado T, Nonomura K, Nissfolk J, Karlsson MK, Hagberg DP, Sun L, Mori S, Hagfeldt A (2009) How the nature of triphenylamine-polyene dyes in dye-sensitized solar cells affects the open-circuit voltage and electron lifetimes. Langmuir 26 2592-2598... 

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