Efficient white organic light‐emitting device by utilizing a blue‐emitter doped with a Red Fluorescent Dopant

Abstract

We synthesized bis (2‐methyl‐8‐quinolinolato)(triphenylsiloxy) aluminum (III) (SAlq), a blue‐emitting material having a high luminous efficiency, through a homogeneous‐phase reaction. The photoluminescence (PL) and electroluminescence (EL) spectra of SAlq show two peaks at 454 nm and 477 nm. Efficient white light‐emitting devices are fabricated by doping SAlq with a red fluorescent dye of 4‐dicyanomethylene‐2‐methyl‐6‐{2‐(2,3,6,7‐tetrahydro‐lH,5H‐benzo[i,j]quinolizin‐8‐yl)vinyl}‐4H‐pyran (DCM2). The incomplete energy transfer from blue‐emitting SAlq to red‐emitting DCM2 results in light‐emission of both blue and orange colors. Devices with the structure of ITO/TPD (50 nm)/SAlq:DCM2 (30 nm, 0.5 %)/Alq₃ (20 nm)/LiF (0.5 nm)/Al show EL peaks at 456 nm and 482 nm originating from SAlq and at 570 nm from DCM2, resulting in the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.32, 0.37). The device exhibits an external quantum efficiency of about 2.3 % and a luminous efficiency of about 2.4 lm/W at 100 cd/m² . A maximum luminance of about 23,800 cd/m² is obtained at the bias voltage of 15 V.

Keywords :

• organic light‐emitting device
• white light‐emitting diode
• electroluminescence
• bis(2‐methyl‐8‐quinolino‐lato)aluminum (III)
• SAlq

Notes

Dept. of Physics, Inha University, 253, Yonghyun‐dong, Nam‐ku, Incheon 402–751, Korea.

Information Display Team. Electronice and Telecommuications Research Institute(ETRI), 161 Gajeong‐Dong, Yuseong‐Gu, Daejeon 305–350, Korea.

Member, KIDS

Student Member, KIDS.