OLEDs typically have a broad emission spectrum with an FWHM of more than 50 nm since π-conjugated organic semiconductors have strong vibronic coupling and structural relaxation when energy transitions from excited to ground states occur. Instead, Platinum- or Boron-based complexes with a rigid backbone shape allow us to overcome the limitations, making them attractive to meet the requirements for next-generation high-performance displays with high color purity. For example, tetradentate type Pt (II)- and Boron-Nitrogen-based complexes can induce narrow emission spectra with an FWHM less than 20 nm for RGB three colors, opening an extra room to extend the color gamut beyond the conventional fluorescent, Ir phosphorescent, and donor-acceptor type thermally activated delayed fluorescence (TADF) emitters. Notably, not only the color purity, Pt (II)- and Boron-Nitrogen-based complexes can achieve high efficiency, almost 100% internal quantum efficiency (IQE), by harvesting singlet and triplet excitons. However, Pt-phosphors typically suffer from triplet-triplet annihilation and triplet-exciton quenching due to the conversion of singlets into triplets via the intersystem crossing (ISC). Instead, multi-resonance (MR) induced TADF emitters based on the DABNA core with Boron and Nitrogen atoms can harvest singlets after reversely converting triplets into singlets via the reverse ISC (RISC), opening a chance to improve the device performance. Here, we developed color bure blue emitting MR emitters.
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