Search

Although multi‐resonance thermally activated delayed fluorescent (MR‐TADF) emitters simultaneously achieve high color purity and high efficiency in organic light‐emitting devices (OLEDs), MR‐TADF‐based OLEDs suffer from severe efficiency roll‐off and lifetime issues for practical application. To overcome these issues, a key solution is hyper OLED technology sensitized by TADF or phosphorescent emitters. In this study, a series of π‐extended phenoxazine‐based asymmetric MR‐TADF emitters for long lifetime, low‐power consumption, and narrow emission band green OLEDs is developed. As a sensitizer, a well‐known phosphorescent emitter is used, fac‐tris(2‐phenylpyridinato‐C2,N)iridium(III) [Ir(ppy)3]. Consequently, these MR‐TADF emitters achieve hyper OLEDs with a power efficiency of 150 lmW−1, an external quantum efficiency of 27%, and a long lifetime LT95 of over 3000 h at high brightness of 1000 cdm−2. These performances are among the best in scientific literature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Homoleptic Ir(III) emitters with electron deficient carbene cyclometalates. • High product selectivity in syntheses. • ∼100 % PLQY and fast radiative rate constant ∼106 s−1 in doped mCPCN thin film. • Achieving >30 % efficiency in the narrowband blue emissive hyper-OLED devices. Blue phosphors are indispensable in constructing organic light-emitting diodes (OLEDs). Herein, we reported two Ir(III) complexes, namely f -CN1 and f -CN2, with asymmetrically arranged benzo[d]imidazolylidenes, to which the peri -cyano substituent has concurrently induced both the selective aryl cyclometalation and emission tuning in giving one single blue Ir(III) phosphor. With the aforementioned 'one stone for two birds' tactics, these carbene complexes exhibited photoluminescent peak (λ max) at ∼472 nm and excellent quantum yields (83–100 %) in doped thin films. Consequently, the fabricated OLED devices delivered maximum external quantum efficiencies (EQE max) of 23.6 % and 20.2 %, respectively. Furthermore, hyper-OLED devices with f -CN1 and multi-resonant TADF terminal emitter m-DiNBO displayed an EQE max of 30.8 % with CIE x,y coordinates of (0.13, 0.10), together with impressive EQE of 26.9 % at practical brightness of 100 cd m−2. [ABSTRACT FROM AUTHOR]