High‐Efficiency Wet‐ and Dry‐Processed Green Organic Light Emitting Diodes with a Novel Iridium Complex‐Based Emitter

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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. 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 (acetylacetonate), are demonstrated. They possess both wet‐ and dry‐processing possibilities. 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 a host, the device shows at 1000 cd m−2 an external quantum efficiency (EQE) of 21% and power efficiency of 64 lm W−1 via vapor deposition, while 26% EQE and 69 lm W−1 by spin‐coating, the highest among all reported wet‐processed green organic light emitting diodes. Besides electroluminescence, 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 a hole, leading to a balanced carrier‐injection, and hence a high carrier recombination and in turn a high device efficiency.

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