Bis‐Tridentate Iridium(III) Phosphors with Very High Photostability and Fabrication of Blue‐Emitting OLEDs

Abstract

Sky‐blue and blue‐emitting, carbazolyl functionalized, bis‐tridentate Ir(III) phosphors Cz‐1–Cz‐3 with bright emission and short radiative lifetime are successfully synthesized in a one‐pot manner. They exhibit very high photostability against UV–vis irradiation in degassed toluene, versus both green and true‐blue‐emitting reference compounds, i.e., fac‐[Ir(ppy)3] and mer‐[Ir(pmp)3]. Organic light‐emitting diodes (OLEDs) based on Cz‐2 exhibit maximum external quantum efficiency (EQE) of 21.6%, EQE of 15.1% at 100 cd m−2, and with CIEx , y coordinates of (0.17, 0.25). This study provides a conceptual solution to the exceedingly stable and efficient blue phosphor. It is promising that long lifespan blue OLED based on these emitters can be attained with further engineering of devices suitable for commercial application.

Cyclometalated Ir(iii) complexes towards blue-emissive dopant for organic light-emitting diodes: fundamentals of photophysics and designing strategies

“…Next, the Chi group employed a carbazolyl unit to replace the phenoxy group. 157 The resultant carbazole-based Ir(III) complexes, 124-126 (Fig. 15), exhibit structureless emission bands indicating the dominant charge transfer contribution in the emissive process, with maxima at 486, 473, and 476 nm, respectively.…”

New aggregation-induced delayed fluorescent materials for efficient OLEDs with high stabilities of emission color and efficiency

“…Conventional fluorescent materials can only harness electrogenerated 25% singlet excitons, which limits the enhancement of their electroluminescence (EL) efficiencies. 6–9 To date, there are some methods for enhancing exciton utilization, such as phosphorescence, 10–12 triplet–triplet annihilation (TTA), 13–16 singlet fission (SF), 17 hybridized local and charge-transfer (HLCT) 18–20 and thermally activated delayed fluorescence (TADF). 21–25…”

Highly Efficient Phosphorescent Blue-Emitting [3+2+1] Coordinated Iridium (III) Complex for OLED Application

“…As shown in Scheme 1A, incorporating the two strong electron-withdrawing groups (dfppy) facilitates the enlargement of the bandgap of iridium (III) complexes by stabilizing the HOMO levels (Holmes et al, 2003) [3+3]. Coordinated iridium (III) complexes show excellence in rigidity and durability due to the stronger metal-ligand bonding interaction, making the d-d excited states or other unspecified quenching states destabilized to enhance the stability of the complexes (Kuo et al, 2017;Kuo et al, 2018;Gnanasekaran et al, 2019;Hsu et al, 2019). Scheme 1B demonstrates a typical [3+3] counterpart, and the interrupted conjugation changes the nature of the frontier orbitals, achieving a blue emission of CIE (0.15, 0.17) (Kuo et al, 2017).…”