Efficient all-solution-processing deep-red polymer light-emitting diodes (PLEDs) based on [Ir(dpqx)2(N^O)]-heteroleptic complexes with asymmetric N^O-ancillary π-donors

Highlights: • [Ir(C^N)₂(N^O)]-heteroleptic Ir(III)-complexes with different asymmetric π-donors are molecularly designed. • Ir(III)-complexes [Ir(dpqx)₂(L¹)] (1) and [Ir(dpqx)₂(L²)] (2) show the efficient deep-red phosphorescence. • All-solution-processed deep-red PLEDs with the attractive electroluminescent performance were realized. Despite concerted efforts to cyclometalated Ir(III)-complexes towards reliable vacuum-deposited/solution-processed deep-red organic/polymer light-emitting diodes (OLEDs/PLEDs), the realization of their all-solution-processed ones with desirable lower-cost, is challenging and rarely reported. In this work, using the Hdpqx (2,3-diphenylquinoxaline) as the C^N main ligand and the asymmetric π-donor HL¹/HL² (HL¹ = (2-(4,5-diphenyl-1H-imidazol-2-yl)phenol); HL² = 2-(1,4,5-triphenyl-1H-imidazol-2-yl)phenol)) as the N^OH ancillary ligand, two C₁-[Ir(C^N)₂(N^O)]-heteroleptic Ir(III)-complexes [Ir(dpqx)₂(L¹)] (1) and [Ir(dpqx)₂(L²)] (2) with efficient deep-red phosphorescence (λ_em = 662–665 nm and Φ_PL = 0.34–0.42) were molecularly designed. Meanwhile, based on the all-solution-processed fabrication, their reliable all-solution-processed deep-red PLEDs with the attractive electroluminescent performance (η_c^Max = 0.51–0.58 cd/A, η_p^Max = of 0.11–0.13 lm/W and η_EQE^Max = 2.08–2.16%; weak (ca. 26–27%) efficiency-roll-offs) were realized.