Voltage reduction of triplet-triplet annihilation upconversion organic light-emitting diode (Conference Presentation)

A emission mode based on triplet-triplet annihilation up conversion (TTAUC) was proposed as follows: when the electrons and holes recombined at the sensitizer layer with a lower energy bandgap, the triplet exciton of sensitizer can transfer the energy to the triplet-triplet annihilation (TTA) emitter and emit a higher energy blue photon. TTAUC-OLEDs had proved to have a higher device efficiency with tris(8-hydroxyquinolinato)aluminum (Alq3) as sensitizer and 9,10-Bis(2-naphthyl)anthraces (ADN) as TTA emitter. In this research, we employed Bis(10-hydroxybenzo[h]quinolinato)beryllium (Bebq2) to replace Alq3 which had a higher electron mobility and resulted in a better electrical properties. It showed a higher current density at constant voltages and the turn-on voltage (at 1 cd/m2) decreased 0.3V compared to Alq3 as sensitizer. Bebq2 as sensitizer achieved a higher efficiency with 3.26% in overall EQE, together with 1.91% and 1.35% in blue and green EQE at J=6.71 mA/cm2 compared to Alq3