Triphenylamine TPA

Borsenberger et al. (1978) measured hole mobilities of TPA doped PC over the same concentration range reported by Pfister. The temperature dependencies were described by an Arrhenius relationship with a high-field activation energy of 0.30 eV. The activation energy was independent of the TPA concentration and weakly field dependent. The concentration dependence gave a wave-function decay constant of 1.8 A. 

Bassler (1984) reexamined Pfister s (1977) data for TPA doped PC. Bassler suggested that the field and temperature dependencies of the mobility could be explained by arguments based on energetic disorder. Bassler extended the same argument to a series of arylalkane derivatives doped into a PC and PS (Pai et al., 1983), and charge-transfer complexes formed between 2,4,7-trinitro-9-fluorenone and poly(N-vinylcarbazole) (Gill, 1972,1976). 

Vannikov et al. (1989, 1989a) measured hole mobilities of TPA doped PS and a PC containing varying concentrations of / -, m-, and o-dinitrobenzene (DNB). The DNB compounds were selected for differences in dipole moment. 

Since these compounds have larger ionization potentials than TP A, it would not be expected that they would be traps. In all cases, however, incorporation of the DNB compounds resulted in a decrease in mobility. According to Vannikov et al., the polarity of the polymer, which is determined by the composition and concentration of DNB molecules, influences the mobility through the polaron activation energy. The field dependencies were explained by a theory due to Marcus (1964). The Marcus theory leads to a field dependence of p E 1 sirih(eEp/2kT). 

Enokida and Hirohashi (1991) measured hole mobilities of 1,1-bis(/ -diethylaminophenyl)-4,4-diphenyl-l,3-butadiene. This is one of few donor compounds that can be prepared from solution as an amorphous layer in the absence of a polymer. At 295 K, the mobilities were in excess of 10-3 cm2/Vs. The field and temperature dependencies were compared to Gill s expression and the disorder formalism. Gill s model gave fiQ = 8 x 10-3 cm2/Vs, TQ = 339 K, A0 = 0.79 eV, and j3 = 2.12 x 10-3 eV (cm/V)1/2. The disorder formalism gave p0 = 1.75 x 10-2 cm2/Vs and a = 0.050 eV. The value of a reported by Enokida and Hirohashi is one of the lowest in the literature. 

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Fujikawa et al. studied a series of triphenylamine (TPA, 14) oligomers from the dimer TPD up to the related pentamer and used them as HTMs [71]. Their results indicated that the thermal stability of the OLEDs was dramatically improved using a HTM TPTE (15) (Scheme 3.9), a tetramer of TPA. The resulting OLED devices show uniform light emission in continuous operation up to 140°C without breakdown [72],... 

Triphenylamine (TPA), AWW W -tetramethyl-p-phenylenediamine (TMPD) and dimethylaniline (DMA) have been popular substrates for reaction under pulse radiolysis conditions. One of the earlier reports dealt with the formation of the radical cation of TMPD by reaction (k = 3 x 108 M 1 s 1) with the peroxy radical derived from oxidation of methylene chloride (CHCI2O2) by pulse radiolysis26. DMA is also oxidized to its radical cation by the same reagent (k = 2.5 x 107 M 1s 1). Since then it has been... 

Triphenylamine (TPA) and isopropylcarbazole (IPC) were used at the beginning as a model doping molecules [287-289]. The introduction into the polymer matrix IPC molecules with a concentration of 102Ocm-3 leads to the clearly seen photogeneration and charge transfer. 

Mittal et al. investigated the electron transfer from diphenylamine (DPA) or triphenylamine (TPA) to two pentaphenylated fullerene derivatives (PPF). The... 

A number of organic solutes undergo reaction with AICI3. For example, aromatic amines dissolve in the room-temperature molten electrolyte butylpyridinium chloride. Triphenylamine (TPA) shows two stages of oxidation upon polarographic examina-... 

It is easy to tell when transport is essentially nondispersive—the current transients approach the ideal, rectangular shape. It is more difficult to tell whether apparently dispersive transport is an intrinsic property of a material. For example, an early study of triphenylamine (TPA)-doped polycarbonate found that the transport was highly dispersive [73q], but later studies of tri-/ -tolylamine (TTA)-doped polymers revealed relatively nondispersive transport [57b, 73r]. Commercial triphenylamine is typically contaminated with A,A,A, A -tetraphenylbenzidine, which contributes very deep sites for hole transport (hole traps) [73s], whereas as-received TTA is apparently free of such impurities. This is probably the reason why the two, very similar materials appear to have very different transport properties. In fact, when TPA is purified adequately, the transport properties approximate those of TTA [73tj. 

UVV spectrophotometry is one of the simplest and fastest methods for determination of aromatic amines and may serve also for identification purpose with the aid of diode array detectors. A study was carried out on the performance of direct phase (silica gel) and RP (Cis) columns, using a MeOH-O.l M NaC104 mobile phase, for the HPLC-UVD (at 256 nm) analysis of five aromatic amines aniline (la), 1- (8a) and 2-napththylamine (9a), di- (DPA) and triphenylamine (TPA). Good resolutions and separation factors were observed with the RP column for la vs. the other analytes and for 8a or 9a vs. DPA or TPA however, separation of the 8a-9a or DPA-TPA pairs was poor210. 

For the case of PFs with HTM on the side chain, the incorporation of triphenylamine (TPA) into PF side chains without the alkyl spacer 14 was carried out by Mullen and coworkers [26] to enhance blue PLED performance. 

The optical absorption spectrum of triphenylmethyl (TPM) in triphenylamine (TPA), which has been investigated by Weissman, is shown in Fig. 31. It seems quite certain that the lowest electronic transition in TPM is a transition (assuming local symmetry ) which is polarized... 

Chart 2.5 Chemical structures of electron-donating compounds triphenylamine (TPA), isopropylcarbazole (IPC), and phenylcarbazole (PhC). 

Fig. 2.11 Doping of an inert polymer, bisphenol A polycarbonate, with triphenylamine (TPA). The quantum yield of charge carrier formation as a function of the TPA content. 2exc=300 nm. Adapted from Borsenberger et al. [52] with permission from the American Institute of Physics.

FIGURE 1.15 Chemical structure of polylfluorene) (PF) and poly(indenofluorene) (PIF). R is either a linear or a branched alkyl chain or bulkier groups such as butoxyphenyl (BP) or triphenylamine (TPA). For PIF, R is either... 

Hence, reactions considered for PVPR illustrate the mechanism connected with the conversions of primary radical cations generated by nitrosyl nitrate. Nevertheless, the direct detection of radical cations by ESR fails in this system apparently because of fast detachment of protons. For confirmation of the ion-radical initiation concept under the action of NO, triphenylamine (TPA) is a suitable model compound. TPA does not contain chemical bonds capable of reacting with monoradicals of NO. The formation of radical cations in TPA has been revealed in reactions with some Lewis... 

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]...

Typical chemical compounds include oxadiazole derivatives [14], pyrazolines [ISIS], hydrazones [19-22], carbazole derivatives [23-26], triphenyhnethane (TPM) derivatives [27, 28], triphenylamine (TPA) derivatives [29, 30], and TAPC [31], which can be regarded as a dimer of TPA. The charge carrier mobilities at room temperature are typically in the range from 10 cmWs for N-isopropylcarbazole [25] to 10 cm A s for p-diethyl-aminobenzaldehyde diphenyl hydrazone (DEH) [22]. 

For PVK at wavelengths between 310 and 350nm, 0g = O.ll [9]. At realistic fields and temperatures the photogeneration efficiency is obviously much lower. For example, at room temperature and E = lO Vm , 0 — 10 . The theory is in excellent agreement with the experimental data on PVK [9] (at least for electric fields above about 3 X 10 Vm" ), solid solutions of AT-isopropylcarbazole (NIPC) in polycarbonate [10] and triphenylamine (TPA) in polycarbonate [11] (Fig. 8.4). 

The transport-active groups can be part of the polymer backbone structure, they can be covalently linked as pendant groups to a vinyl or similar chain such as carbazole groups (substituted aromatic amines) in PVK, or need not be covalently attached to the polymer backbone at all. Indeed, solid solutions of NIPC in polycarbonate display hole mobilities that are comparable to those in PVK [19, 20]. The polymer backbone in PVK does not contribute to transport, but merely ties the transport-active groups together. Similarly, both solid solutions of triphenylamine (TPA) in polycarbonate [21] and poly (methacrylate) with pendant triphenylamine groups [22] display photoconductivity and charge transport. 

To achieve highly stable BHJ thin-film morphology, amorphous PCBM derivatives have been developed by Jen and co-workers (Scheme 3.3). They synthesized PCBM derivatives having bulky aromatic groups such as triphenylamine (TPA) and 9,9-dimethylfiuorene (MF). The TPA-PCBM (10) and MF-PCBM (11) obtained have high glass transition temperatures, Tg, of... 

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