A PCDTBT:PC71BM solar cell adopted by a ternary strategy with PDTSTPD achieves an overall PCE of 20.8% under indoor illumination.

Herein, a series of blue‐emitting Ir(III) phosphors is reported based on the cyclometalating N‐heterocyclic carbenes (NHCs), in which the typical benzimidazolylidene entity is now replaced by a new 7,9‐dihydro‐8H‐purin‐8‐ylidene unit. The two extra‐nitrogen atoms of benzimidazolylidene entity that are successfully fined turn the emission to the true‐blue region. As the proof of concept, both experimental measurement and theoretical calculation of these emitters are conducted, revealing high photoluminescence quantum yields up to 92%, peak maximum located in the region 420–490 nm, and radiative lifetime lower than 1 μs, depending on their stereochemical configuration (i.e., meridional or facial), together with distinctive phenyl cyclometalating appendage. Their photophysical characteristics are among the best of carbene‐based Ir(III) blue phosphors. Blue phosphorescent organic light‐emitting diode (OLED) using one representative derivative m‐2tBu as sole dopant emitter achieves a high external quantum efficiency (EQE) up to 17.0%, and a small efficiency roll‐off of 16% at 1000 cd m−2. Furthermore, a true‐blue hyperphosphorescent OLED with 25 wt% of m‐2tBu as sensitizer and 2 wt% of N7,N7,N13,N13,5,9,11,15‐octaphenyl‐5,9,11,15‐tetrahydro‐5,9,11,15‐tetraaza‐19b,20b‐diboradinaphtho[3,2,1‐de:1′,2′,3′‐jk]pentacene‐7,13‐diamine (ν‐DABNA) as emitter is also fabricated, giving excellent performance with maximum EQE up to 22.0% and Commission Internationale de l’Éclairage (CIE)xy coordinates of (0.120, 0.155).

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Four blue-emissive iridium­(III) complexes bearing a 3,3′-(1,3-phenylene)­bis­[1-isopropyl-6-(trifluoromethyl)-3H-imidazo­[4,5-b]­pyridin-2-ylidene]-based pincer chelate, which are derived from PXn·H3(PF6)2, where n = 1–4, and a cyclometalating chelate given from 9-[6-[5-(trifluoromethyl)-2λ2-pyrazol-3-yl]­pyridin-2-yl]-9H-carbazole [(PzpyCz)­H2], were successfully synthesized and employed as both an emissive dopant and a sensitizer in the fabrication of organic light-emitting diode (OLED) devices. These functional chelates around a IrIII atom occupied two mutually orthogonal coordination arrangements and adopted the so-called bis-tridentate architectures. Theoretical studies confirmed the dominance of the electronic transition by the pincer chelates, while the dianionic PzpyCz chelate was only acting as a spectator group. Phosphorescent OLED devices with [Ir­(PX3)­(PzpyCz)] (B3) as the dopant gave a maximum external quantum efficiency (EQE) of 21.93% and CIE xy of (0.144, 0.157) and was subjected to only ∼10% of roll-off in efficiency at a high current density of 1000 cd m–2. Blue-emissive narrow-band hyperphosphorescence was also obtained using B3 as an assistant sensitizer and ν-DABNA as a terminal emitter, giving both an improved EQE of 26.17% and CIE xy of (0.116, 0.144), confirming efficient Förster resonance energy transfer in this hyperdevice.

Efficient blue phosphors remain as the formidable challenges for organic light‐emitting diodes (OLEDs). To circumvent this obstacle, a series of Ir(III) based carbene complexes bearing asymmetric di‐N‐aryl 6‐(trifluoromethyl)‐2H‐imidazo[4,5‐b]pyridin‐2‐ylidene chelates, namely, f‐ct6a ‒ c, were synthesized and their structures and photophysical properties were comprehensively investigated. Moreover, these emitters can undergo interconversion in refluxing 1,2,4‐trichlorobenzene, catalyzed by a mixture of sodium acetate (NaOAc) and p‐toluenesulfonic acid monohydrate (TsOH·H2O) without decomposition. All Ir(III) complexes present good photoluminescence quantum yield (ΦPL = 83 – 88%) with peak maximum (max.) at 443 ‒ 452 nm and narrowed full width at half maximum (FWHM = 66 – 73 nm). Among all fabricated OLED devices, f‐ct6b delivered a max. external quantum efficiency (EQE) of 23.4% and Commission Internationale de L'Eclairage CIE(x,y) coordinates of (0.14, 0.12), whereas the hyper‐OLED device based on f‐ct6a and 5H,9H,11H,15H‐[1,4] benzazaborino [2,3,4‐kl][1,4]benzazaborino[4′,3′,2′:4,5][1,4]benzazaborino[3,2‐b]phenazaborine‐7,13‐diamine, N7,N7,N13,N13,5,9,11,15‐octaphenyl (ν‐DABNA) exhibited max. EQE of 26.2% and CIE(x,y) of (0.12, 0.13). Finally, the corresponding tandem OLED with f‐ct6b as dopant gave a max. luminance of over 10000 cd⋅m‒2 and max. EQE of 42.1%, confirming their candidacies for making true‐blue OLEDs.This article is protected by copyright. All rights reserved