Singlet-Exciton Harvesting Fluorescent Organic Light-Emitting Diodes with 9,9-Diphenyl-9,10-dihydroacridine diphenyl sulfone derivative

Abstract

In Organic Light Emitting Diodes(OLEDs) research, red and green phosphorescent devices have acheived high external quantum efficiency ( and long lifetime but blue phosphorescent devices suffer from unstability and short lif etime due to high triplet energy. For these reasons, study on enhancing EQE of blue fluorescent devices which is limitted to 25% internal quantum efficiency(IQE) theorically, has been actively e xcecute d As a third generation of OLED materials, t hermally a ctivated d elayed f luorescence (TADF ) materials have attracted much intertest because 100% I QE can be acheived by th e i r s m a ll Δ E ST . I n this work, we used deep blue 9,9 Diphenyl 9,10 dihydroacridine diphenyl sulfone derivative (DPS D1) as assistant dopant so that it can harvest triplet excitons from host and effectively transfer singlet excitons to fluorescent emitter. Fig . 1 (a) shows the EQE luminance characteristics of devices. In p articula r the device without/with DPS D1 showed external quantum efficienc y of 3.22 % 6.07 % and max luminance of 25.9 c d/m 2 , 635.6 9 c d/m 2 r espectively. Figure 1. (a) inset shows normalized electroluminescence (EL) spectra of the device s without/ with DPS D1 maximum intensity at 462nm Fig. 1. (b) shows device structure fabricat ed in following sequence; indium tin oxid e (ITO) (150 nm) / tris(4 carbazoyl 9 ylpheny l )amine(TCTA) (50nm) / bis[2 --(diphenyl phosphino)phenyl] ether oxide(DPEPO) : DPS D1 x wt : 2,5,8,11 tetra tert butylperylene(TBPe) 3% (25nm) / 2,2’,2’’ 2’’--(1,3,5 Benzinetr iyl) tris(1 phenyl 1 H benzimidazole) (TPBi) (30nm) / 8 Quinolinolato lithium (Liq) (2nm) / Al (100nm) It was found that the device using DPS D1 as a sensitzer has much high efficiency compared to the device without DPS D1. Further details will be discuss ed.