Recent progress and prospects of fluorescent materials based on narrow emission

Thermally activated delayed fluorescence (TADF) emitters have been rapidly developed over a decade, and they all have efficiencies in excess of 35% in the visible range. Despite their high external quantum efficiency, the broad 70-110 nm emission spectra and short device lifetime have limited their commercialization. The recent rapid development of multiple resonance (MR) TADF materials with narrow emission has made them attractive to industry. Hence, high color purity MR-TADF materials are expected to be fourth-generation emitters for high definition (HD) organic light-emitting diodes (OLEDs). In this review, we systematically document the TADF emitters based on MR frameworks to date, including molecular design, material structure-photophysical properties and device characteristics. In addition, the molecular design guidelines and future commercial prospects of full-color MR-TADF emitters are envisaged.