A new benzimidazole/carbazole hybrid bipolar material for highly efficient deep-blue electrofluorescence, yellow–green electrophosphorescence, and two-color-based white OLEDs

Abstract

The bipolar molecule CPhBzIm exhibits an excellent solid state photoluminescence quantum yield (Φ_PL = 69%), triplet energy (E_T = 2.48 eV), and bipolar charge transport ability (μ_h ≈ μ_e ≈ 10⁻⁶–10⁻⁵ cm² V⁻¹ s⁻¹). We have used it to fabricate a non-doped deep-blue organic light emitting diode (OLED) exhibiting promising performance [η_ext = 3%; CIE = (0.16, 0.05)] and to serve as host material for a yellow–green phosphorescent OLED [η_ext = 19.2%; CIE = (0.42, 0.56)]. Exploiting these dual roles, we used CPhBzIm in a simple singly doped, two-color-based white OLED (η_ext = 7%; CIE = 0.31, 0.33).