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.


S4
General Synthesis of main ligands.Scheme S1.Synthetic route for main ligands.

Computational details and data
Density functional theory (DFT) and time−dependent density functional theory (TDDFT) calculations were performed to understand the geometries and the electronic structures of −−TMS and −−TMS using the Gaussian 16 package. 20The vibrational frequency calculations at the same level were carried out to verify that every optimized structure is an energy minimum (no imaginary frequency).PBE0 21         following literature [26] , by assuming an acceleration factor of 1.8.
Scheme S2.Synthetic route for iridium complexes.

, 6 −
31G*(IANI2DZ)22− was used for both the geometry optimization and TDDFT calculations.The solvent effects were examined using the self−consistent reaction field (SCRF) method based on PCM models.24−25The choice of solvents (DCM, a dielectric constant  = 8.93) was based on the solvent media for experiments.Calculated first 15 singlet excited state energies ( / nm), the associated oscillator strengths (f) and the nature of the transitions at the optimized ground state (S0) geometries of −−TMS and −−TMS in the dichloromethane (DCM) by TD−PBE0.The values in the parentheses are the % contributions of that particular configuration state function (CSF).

Figure S27 .Figure S28 .
Figure S27.Simulated absorption spectrum of −−MS.The red vertical lines refer to the unbroadened oscillator strengths of the singlet-singlet transitions, and the black line is the fitting line of the UV−vis absorption.

S19 Crystallography Table S3 .
Selected Bond Lengths and Angles for Complexes PB−−S and

Table S8 .
Cartesian coordinates for optimized structures of −−MS.

Table S9 .
Cartesian coordinates for optimized structures of −−MS.