70.2: Low‐Voltage White Tandem Structures for Fabricating RGBW AMOLED Displays

Abstract

Abstract We recently demonstrated full‐color RGBW AMOLED displays based on white‐emitting OLED structures optimized for a D65 white point. The efficiency of the white formulation has been improved by the use of tandem structures with two or three lowvoltage white‐emitting units connected by organic “PN”‐type connectors. It has been found that the separation between emitting units is critical to the efficiency and the white point of the tandem structure. Optimized two‐ and three‐EL unit structures exhibit efficiencies of 17.4 cd/A and 24.6 cd/A, respectively, compared to 10.7 cd/A for the single‐EL unit control. The tandem structures demonstrate excellent operational stability, with extrapolated half‐life times for one‐, two‐, and three‐unit test devices of about 50,000 h, 70,000 h, and 110,000 h, respectively, at 1000 cd/m 2 . We have also fabricated advanced white tandem structures where the color gamut (NTSC x,y ratio) has been improved to greater than 70% using standard color filters.