Small molecules with pyridine backbone modified with carbazole, fluorine and bromine for white light-emitting diode applications

• Molecules with pyridine as the backbone and modified by carbazoles were synthesized.
• The molecules exhibit sharp blue fluorescence and excimer orange emission.
• Structurally, bromo was identified as a crucial factor to generate excimer emission.
• The molecules were made into simple structured OLED devices and emit white emission.

Seven compounds with pyridine as the backbone modified by carbazole moiety, bromine atom and fluorine atom were synthesized. Compounds 1, 2, 3 with bromo substitution at the 2-position and carbazole modification at the 5-position of pyridine emit not only a sharp blue singlet fluorescence but also a wide banded excimer-based orange emission. The two colors coming from a single molecule can be used to fabricate a simplified white light emitting device. The electroluminescence based on 1 and 2 exhibits white-light emission with CIE coordinates of x = 0.25 and y = 0.30 for 1 and x = 0.33 and y = 0.37 for 2 at high current densities, very close to pure white emission. In addition, the role of bromo-substitution at pyridine is concluded to be essential to generate molecular interaction thus an excimer emission.