High efficiency and long lifetime fluorescent white organic light-emitting diodes by phosphor sensitization to strategically manage singlet and triplet excitons. Issue 10 (22nd February 2021) - Yao, Jingwen
Abstract : The positions of the phosphor-sensitized yellow EML from the exciton recombination zone were controlled to strategically utilize singlet and triplet excitons for blue and yellow emissions to realize high-performance fluorescent WOLEDs. Abstract : All fluorescent white organic light-emitting diodes (WOLEDs) have the advantages of low cost, low-efficiency roll-off, and good stability. However, how to utilize all singlet and triplet excitons for radiative emission through device structure design to effectively manage excitons in fluorescent WOLEDs is still a challenge. Here, we have successfully realized high efficiency, low-efficiency roll-off and long lifetime fluorescent WOLEDs by strategically controlling the position of the phosphor-sensitized fluorescent yellow emitter in the Bepp2 layer so that singlet excitons are used for blue emission and triplet excitons for the yellow emission. The yellow emission layer is composed of the phosphor sensitizer Ir(ppy)3 and yellow fluorescent emitter TBRb co-doped in Bepp2 . The resulting complementary-color fluorescent WOLEDs exhibited the maximum current efficiency of 46.8 cd A −1, power efficiency of 56.5 lm W −1 and external quantum efficiency of 15.2%; these efficiency values remained at 32.7 cd A −1, 28.6 lm W −1 and 10.9% at the luminance of 1000 cd m −2 . The operational lifetime LT50 (decay to half of the initial luminance) of optimized WOLEDs was up to 1680 h at an initial luminance of 1000 cd m −2 . This strategy design proposes a potential route to achieve high-performance fluorescent WOLEDs for practical applications.