Abstract
High efficiency green emission is crucial to the designs of energy-saving display and lighting. Efficient electroluminescent green emitters with both wet- and dry-process feasibility is highly desirable in order to realize, respectively, cost-effective large roll-to-roll manufacturing and high performance products. We demonstrate in this study high efficiency phosphorescent green organic light-emitting diodes with a novel iridium complex, bis[5-methyl-8-trifluoromethyl-5H-benzo(c)(1,5)naphthyridin- 6-one] iridium (acetyl acetonate), possessing both wet- and dry-process feasibility. The emitter exhibits a short excited-state lifetime, 1.25 μs, and a high quantum yield, 69%, due to the efficient intersystem crossing of the ground-state to the excited-state. Using 4,4’-bis(carbazol-9-yl) biphenyl as host for example, the device shows at 1,000 cd m-2 an external quantum efficiency (EQE) of 21%, current efficiency of 77 cd A-1 and power efficiency of 64 lm W-1 via vapor deposition, while 26% EQE, current efficiency of 77 cd A-1 and 69 lm W-1 by spin-coating, the highest among all reported wet-processed green organic light-emitting diodes. Besides the electroluminescence effective emitter, the high device efficiency may also be attributed to the employed device architecture enabling therein an electron trap to facilitate the injection of this minor carrier against that of hole, leading to a balanced carrier-injection, and hence a high carrier recombination and in turn a high device efficiency.