Efficient deep-blue organic light-emitting diodes with low driving voltage and high color purity

A high performance deep-blue electroluminescent device was prepared by employing bis(2-(2-hydroxyphenyl)-pyridine)beryllium (Bepp2) as a fluorescent guest material with an energy level matching host material. Device structure and thickness of individual layer were also optimized to reduce accumulation holes, balance carriers' distribution on emitter molecules, and eliminate the penetration of electrons via hole dominant light-emitting layer. Consequently, exciplex emission was efficiently eliminated, which is helpful in improving color purity and enhancing luminescent efficiency. Finally, deep-blue device with Commission Internationale de L'Eclairage (CIE) coordinate of (0.150, 0.096) was obtained, and the optimal device realized the highest brightness of 11780 cd m−2, current efficiency (ηc) of 2.40 cd A−1, power efficiency (ηp) of 2.35 lm W−1, and external quantum efficiency (EQE) of 3.0%.