Date

Place

Room B (Room 324)
30. OLED Device I
August 20, 2015 (Thursday)
11:00 ~ 12:35

[30-3]
11:40 ~ 11:55
Title:Highly Efficient Organic Light Emitting Diodes with Transparent Electrode Adopting Low Refractive Index Material
Jongseok Han (Seoul Nat'l Univ., Korea), Hyung-jun Song (Los Alamos Nat'l Laboratory, U.S.A.), Yongwon Kwon, Jiho Sohn, and Changhee Lee (Seoul Nat'l Univ., Korea)
Abstract: In spite of great opto-electrical properties of?indium tin oxide (ITO), it has been pointed out that the waveguide of emitting light, caused by the difference of refractive index (n) between ITO (n =~1.8) and glass substrate (n=~1.5), is a main obstacle to reduce external quantum efficiency of OLEDs. To solve this issue, transparent electrode consists of dielectric/thin metal/dielectric (DMD) structures, such as WO3/Au/WO3 or Ta2O5/Ag/WO3, were successfully employed to OLEDs for enhancing optical out-coupling efficiency. However, the refractive index difference between dielectric layer and glass substrate is a still bottleneck to achieve highly efficient OLEDs.?Here, we demonstrated highly efficient OLED with transparent electrode employing soft material, whose refractive index is very similar with that of glass, replacing the bottom dielectric layer having high refractive indices. To enhance the efficiency of OLEDs, we replaced ITO to thin Ag film sandwiched by soft material (1 um) and 25 nm of 4,4��-Cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC) doped by molybdenum oxide(MoO3, 25%, volume ratio).?The device with transparent electrode using low refractive index material showed current efficiency of 148.8 cd/A at 1000 cd/m2, indicating light outcoupling enhancement of more than 300 % compared to that of ITO anode (43.5 cd/A).
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