Reduced Efficiency Roll-Off of Terdentate Chloroplatinum Emitter-Based Solution-Processed OLEDs Through an Oxygen-Bridged N∧C∧N Polypyridyl Ligand

Platinum complexes are highly promising emitters in the development of high-performance organic light-emitting diodes (OLEDs). However, solution-processed OLEDs of platinum complexes suffer from the severe efficiency roll-off at high luminance that greatly impede their commercial applications. To address this issue, three terdentate chloroplatinum emitters Pt1 − Pt3 are designed and synthesized by using oxygen-bridged N ∧ C ∧ N terdentate ligands to suppress efficiency roll-off in device. As indicated by the X-ray single-crystal analysis, these emitters possess similar square-planar configuration but exhibit different intermolecular interactions. Among them, Pt1 achieves excellent solubility (∼21 mg mL −1 ), good film-forming ability, high photoluminescence quantum yield (91%), and short excited-state lifetime (2.58 μs). Solution-processed OLEDs based on Pt1 exhibit a maximum external quantum efficiency (EQE max ) of 15.02% with a small efficiency roll-off (Roll-off 1000 = 6.72%) at the practical luminance brightness level of 1000 cd m −2 . More importantly, the large-area (100 mm 2 ) OLEDs of Pt1 with a decent EQE max of 6.01% and a negligible efficiency roll-off (Roll-off 1000 = 0.99%) at 1000 cd m −2 have been realized, representing one of the highest performance recorded to date based on the terdentate platinum complexes. This work provides an effective molecular design strategy to develop terdentate platinum emitter-based highly efficient solution-processed OLEDs with small efficiency roll-off.