Deep-blue high-efficiency triplet-triplet annihilation organic light-emitting diodes using donor- and acceptor-modified anthracene fluorescent emitters

Deep-blue organic electroluminescence (EL) emitters are important for full-color display and solid-state lighting applications of organic light-emitting diode (OLED) technology. Triplet‒triplet annihilation (TTA) is one efficient approach for realizing efficient deep-blue EL. In this study, a PPI donor and a BI acceptor are connected via an anthracene (AN) bridge to obtain a bipolar deep-blue TTA emitter, PPI-AN-BI. The effects of the donor and the acceptor moieties are studies by comparing photophysical properties of molecules obtained by replacing either the PPI or the BI group with a phenyl (P) group to obtain BI-AN-P or PPI-AN-P. Nondoped OLEDs based on the three molecules display high-performance deep blue electroluminescence (EL). Using PPI-AN-BI as a nondoped emitter, a trilayer device exhibits a maximum external quantum efficiency (EQE) of 8.4% with CIE (0.15, 0.15) and a bilayer device exhibits a maximum external quantum efficiency (EQE) of 6.9% with CIE (0.15, 0.15). It is experimentally and theoretically demonstrated that triplet pair transition and enhanced oscillator strength can be the main reasons contributing to the high performances. This work would provide an efficient method for designing deep-blue nondoped EL emitters.