Next-Generation Blue OLED Emitters: Efficiency, Color Purity, and the Road to BT.2020

Abstract

Next-generation ultrahigh-definition (UHD) displays demand blue organic light-emitting diodes (OLEDs) that can achieve high efficiency, long operational stability, and the stringent color purity required by the BT.2020 standard. Though thermally activated delayed fluorescence (TADF) and phosphorescent emitters enable full exciton utilization, conventional donor-acceptor TADF systems typically exhibit broad emission spectra arising from long-range charge-transfer character. Ultimately, limiting their color purity. Multiple-resonance (MR) TADF materials deliver intrinsically narrowband emission through short-range charge-transfer transitions induced by orthogonally arranged resonance atoms. In this comprehensive material review, we describe molecular design strategies for high-performance blue MR-TADF emitters, emphasizing boron-nitrogen, carbonyl-nitrogen, and indolocarbazole-based molecular frameworks. We discuss how structural engineering such as π-extension, peripheral shielding, spiro-locking, carbonyl incorporation, and heteroatom modulation assists precise control of HOMO-LUMO distributions, suppress vibronic coupling, and enhances reverse intersystem crossing to achieve narrow emission bandwidths (<20 nm) with high photoluminescence quantum yields. In addition, key device-engineering approaches, including phosphorescence-sensitized fluorescence and TADF-sensitized fluorescence, further mitigates exciton loss, efficiency roll-off, and aggregation-induced quenching in practical devices. By integrating molecular and device design perspectives, this review highlights the current progress, remaining challenges, and future opportunities in realizing efficient, stable, and spectrally pure blue MR-TADF OLEDs suitable for next-generation display applications.