Spirobifluorene Core-Based Novel Hole Transporting Materials for Red Phosphorescence OLEDs

Two new hole transporting materials, named HTM 1A and HTM 1B, were designed and synthesized in significant yields using the well-known Buchwald Hartwig and Suzuki cross- coupling reactions. Both materials showed higher decomposition temperatures (over 450 °C) at 5% weight reduction and HTM 1B exhibited a higher glass transition temperature of 180 °C. Red phosphorescence-based OLED devices were fabricated to analyze the device performances compared to Spiro-NPB and NPB as reference hole transporting materials. Devices consist of hole transporting material as HTM 1B showed better maximum current and power efficiencies of 16.16 cd/A and 11.17 lm/W, at the same time it revealed an improved external quantum efficiency of 13.64%. This efficiency is considerably higher than that of Spiro-NPB and NPB-based reference devices.