High efficiency, ultra-low roll-offs in orange phosphorescent organic light-emitting devices using a novel exciplex system

The exciplex system is expected to be able to address the serious efficiency roll-offs that restrict the organic light emitting devices(OLEDs) further developments. A novel exciplex system is achieved with high efficiencies and reported the effects with different donor/acceptor ratios. The exciplex system is formed by the donor of 4,4'-cyclohexylidenebis[N,N-bis(p-tolyl)aniline] (TAPC) and the acceptor of 1,3-dihydro-1,1-dimethyl-3-(3-(4,6 diphenyl-1,3,5-triazin-2-yl)phenyl)indeno-[2,1-b]carbazole (DMIC-TRZ). The exciplex devices achieve a maximum current efficiency of 25.12 cd/A by adjusting the ratio of donor and acceptor systematically. To further explore the roll-offs reducing from the exciplex system, the orange phosphorescent OLED is fabricated by employing the exciplex system realizing a maximum current efficiency(CE) of 61.15 cd/A, and the roll-off of just 0.13% from the maximum CE to the CE at 1000 cd/m2. The exceedingly low roll-off in orange PHOLEDs is attributed to the effective energy transfer processes and the extremely balanced charge-transporting abilities.