New [3+2+1] Iridium Complexes as Effective Phosphorescent Sensitizers for Efficient Narrowband Saturated–Blue Hyper–OLEDs

Abstract

Two newly designed and synthesized [3+2+1] iridium complexes through introducing bulky trimethylsiliyl (TMS) groups are doped with a terminal emitter of v–DABNA to form an coincident overlapping spectra between the emission of these two phosphors and the absorption of v–DABNA, creating cascade resonant energy transfer for efficient triplet harvesting. To boost the color quality and efficiency, the fabricated hyper‐OLEDs have been optimized to achieve a high external quantum efficiency of 31.06%, which has been among the highest efficiency results reported for phosphor sensitized saturated‐blue hyper‐OLEDs, and pure blue emission peak at 467 nm with the full width at half maxima (FWHM) as narrow as 18 nm and the CIEy values down to 0.097, satisfying the National Institute of Standards and Technology (NIST) requirement for saturated blue OLEDs display. Surprisingly, such hyper‐OLEDs have obtained the converted lifetime (LT50) up to 4552 h at the brightness of 100 cd m−2, demonstrating effective Förster resonance energy transfer (FRET) process. Therefore, employing these new bulky TMS substituent [3+2+1] iridium(III) complexes for effective sensitizers can greatly pave the way for further development of high efficiency and stable blue OLEDs in display and lighting applications.

High efficiency and high color purity deep‐blue organic light‐emitting diodes with blue index >500

“…In the cascade energy transfer process of PSF OLED system, FRET process from triplets of phosphor sensitizer to singlets of terminal emitter is the dominating factor rather than Dexter energy transfer (DET) process. 17 Effective FRET can reduce triplet exciton accumulation, resulting in better device performance (Figure 1). Therefore, in order to achieve the most efficient energy transfer process, the sensitizer and emitter should be elaborately selected and matched.…”

Bis-tridentate Ir(III) Phosphors and Blue Hyperphosphorescence with Suppressed Efficiency Roll-Off at High Brightness

“…Scheme ) were known to possess the enhanced metal–chelate bond strength imposed by the stronger Ir–C covalent character. Hence, the carbene pincer chelate allows for an effective destabilization of metal-centered (MC) dd excited states, and notably increases both the radiative rate and emission quantum yields of the corresponding bis-tridentate (or 3 + 3 type) Ir­(III) emitters in giving efficient room-temperature luminescence. − In recent times, the pimb chelate and analogues are also employed in the design of alternative 3 + 2 + 1-based Ir­(III) complexes for efficient phosphorescent OLED applications. − …”