Novel functional materials based on triarylamines–synthesis and application in electroluminescent devices and photorefractive systems

Abstract

A variety of new functional materials based on triarylamines, such as low molecular weight glasses which possess hole conducting/photoconductive properties as well as amorphous bifunctional materials which combine photoconductive and non-linear optical (NLO) properties in one compound, have been synthesized. The new hole transporting glasses belong to the class of 1,3,5-tris(triaryldiamino)benzenes (TTADB). The hyperbranched structure and the large aryl groups attached as substituents lead to high glass transition temperatures of up to 141 ¡C in these compounds. The TTADBs do not recrystallize upon cooling from the (T g ) melt, but form stable glasses. Cyclic voltammetry studies reveal multi-oxidation stages for these compounds of which the Ðrst oxidation is reversible. The HOMO energy values determined from CV for TTADB-1 and TTADB-2 are [4.82 and [4.94 eV, respectively. Light emitting diodes with the structure ITO/TTADB-2/Alq3/Al (where ITO \ indium tin oxide) show high efficiency and large current carrying capacity. Further, bifunctional compounds have been synthesized in which a photoconductive moiety such as bis(carbazolyl)triphenylamine or bis(diphenylamino)triphenylamine is covalently bound to di †erent NLO chromophores. Some of these compounds are thermally and morphologically stable amorphous materials, possessing in the range from 85 to 122 ¡C. Cyclic voltammetry measurements reveal that the HOMO energy T g values are between [4.81 and [5.45 eV. In photorefractive measurements using 40 lm thick samples, a di †raction efficiency of 27%, which corresponds to a refractive index modulation (*n) of 3.5 ] 10~3, a maximum two beam coupling gain coefficient (C) of 90 cm~1 and a response time of 40 ms were obtained.

Molecular hosts for triplet emitters in organic light-emitting diodes and the corresponding working principle

“…where E ref is the reference, with values of 4.7 eV for Ag/AgCl [54], 4.4 eV for SCE (saturated calomel electrode) [55], 4.8 eV for ferrocene [52], and 4.6 eV for NHE (normal hydrogen electrode) [56]. LUMO can be deduced from the long wavelength cutoff ( cutoff , nm) of the absorption spectrum and the HOMO:…”

Photorefractivity in a bi-functional polymer nanocomposites sensitized by CdS nanoparticle

“…Here, semiconductor nanoparticles are the class of polymer photosensitizers, and the photoconductivity enhancement of polymer has been demonstrated when CdS and other semiconductor nanoparticles were finely dispersed in the polymer matrix [5][6][7][8] due to the carrier transfer effect between the dopants and polymer [9] . Recently, the photorefractive effect can be observed in the bi-functional PR polymers [10][11][12] that exhibits photoconductivity and electro-optic properties. It can have been investigated intensively due to their high stability and easy synthesis.…”

3,3'-(1,4-Phenylenebis(phenylazanediyl))bis(7-ethoxy-4-methyl-2H-chromen-2-one)

“…Coumarin derivatives have attracted much interest owing to their potential applications in organic light-emitting diodes (OLEDs) [3]. The arylamine moiety fulfills the requirement of easy and reversible oxidation and therefore constitutes the building block of many of the hole-transporting materials [4].…”

“…Coumarin derivatives have attracted much interest owing to their potential applications in organic light-emitting diodes (OLEDs) [3]. The arylamine moiety fulfills the requirement of easy and reversible oxidation and therefore constitutes the building block of many of the hole-transporting materials [4].N,N'-diphenylbenzene-1,4-diamine was synthesized from p-phenylenediamine and bromobenzene by known procedure [5]. A yellow solid with melting point 135 °C was obtained.…”