Efficient synthesis and structural effects of ambipolar carbazole derivatives

- Linear and star-shaped carbazole-based ambipolar molecules were synthesized.
- The star-shaped architecture improve hole and electron mobility.
- Formation of exciplexes between the studied compounds and bathocuproine was found.
- OLED based on the star-shaped compound and bathocuproine shows white emission.

A new class of carbazole derivatives, with varying degree of core substitution was synthesized and characterized. The presented synthetic route requires mild conditions, starts from low-cost substrates and leads to the formation of the target products with good yields. The optical and electronic properties of the synthesized materials were estimated and supported by DFT calculations. Investigated compounds emit violet light with quantum efficiency reaching 18.2%. Electrochemical and electron photoemission spectroscopy revealed that ionization potentials are in range of 5.10-5.30 eV. Time-of-flight measurements revealed that those compounds have balanced hole and electron mobility in range of 4.27·10−6-8.42·10‐5 cm2/Vs for star-shaped compound and 6.2 × 10−7-6.2 × 10−6 cm2/Vs for linear derivatives. Electroluminescence spectra of the OLED device prepared using the newly synthesized compounds were characterized by broad emission in visible range, resulting in white light generation.

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