2017 Volume 74 Issue 6 Pages 508-516
In order to develop thermally stable hole transporting polymers, the N-arylcarbozole moiety, which was connected at 3,9-positions, was incorporated into 4-butyltriphenylamine based polymers via Pd-catalyzed C-N coupling polymerization. The synthesized copolymers have number average molecular weights in the range from 7.3 to 12 kg/mol, and are soluble in chloroform and chlorobenzene. UV-vis spectra revealed that the introduction of carbazole moiety leads to the blue-shift of wavelength at the absorption maximum, and thus to the extension of the band gap. Other optical and electrochemical properties were evaluated by fluorescent spectroscopy and cyclic voltammetry. From DSC measurements, it is found that the glass transition temperatures of copolymers are higher than that of the homopolymer consisting of 4-butyltriphenylamine units. The copolymer with 70 mol% of carbazole units shows a glass transition at 267°C. Investigation of space-charge limited current characteristics in the hole-only devices reveals that the introduction of carbozole unit improves the hole mobility, and the above-mentioned copolymer shows a hole mobility of 1.5 × 10−5 cm2 V−1 s−1.
