Electroluminescent properties of OLEDs using 1,2-BBPE derivatives

Abstract

We fabricated the organic light emitting diodes (OLEDs) using 1,2-BBPE (1,2-bisbiphenyl ethene) derivatives as a blue emitting material, which was synthesized from the 4,4'-dibromo stilbene. The methyl and tert-butyl groups were incorporated at the 4" and 4''' positions of 1,2-BBPE: 1,2-bis(4",4"'-dimethylbiphenyl)ethene (BMBPE) and 1,2-bis(4",4"-di-tert-butylbiphenyl)ethene (BTBBPE). Photo-luminescence (PL) maxima were 439 nm for BMBPE and 425 nm for BTBBPE deposited as a film with the thickness of 1000 A. The single-layer device fabricated with BMBPE exhibited electroluminescent (EL) maxima at 440 and 422 mn. The brightness of the luminescence observed from the device was 50 cd under 19 V. The FWHM (full-width half-maximum) observed from the EL device was 55 m. The luminescence intensity generated from the OLED made with a single BBPE layer emitted low intensity light at 422 and 442 nm and the FWHM was 61 nm. The multi-layer device with NPB, Alq(3), BCP for the hole blocking layer and BTBBPE as emission material showed luminescence intensity over 2000 Cd/m(2). We investigated the luminescence property as a function of device structure, such as layer thickness, chemical structure dependence.