Carbazole-based bis(enamines) as effective charge-transporting amorphous molecular materials

Abstract

A series of carbazole-based bis(enamines) as glass-forming hole transport materials has been synthesized and characterized. The amorphous films of the reported compounds demonstrate extraordinarily high hole-drift mobilities reaching 5 × 10 −2 cm 2/V s at high electric fields. To our knowledge this is one of the highest values observed to date for amorphous molecular p-type semiconductors. The reported compounds constitute materials with high thermal stability with five percent weight loss temperatures exceeding 370 °C as characterised by thermogravimetric analysis. They form glasses with the glass transition temperatures ranging from 83 to 126 °C as established by differential scanning calorimetry. Photoelectric properties of the materials were examined by electron photoemission and time of flight technique. The electron photoemission spectra of the layers revealed the ionization potentials as low as 4.98–5.15 eV.