Blue Multiresonance Thermally Activated Delayed Fluorescence Conjugated Polymers for Solution-Processable Narrowband Blue Organic Light-Emitting Diodes with High Color-Purity

Thermally activated delayed fluorescence (TADF) conjugated polymers generally exhibit red-shifted photoluminescence (PL) spectra compared to their TADF chromophores, owing to the extension of conjugation along the polymeric backbone. Developing blue TADF-conjugated polymers, particularly those with high color purity, continue to pose a significant challenge. Herein, we design and synthesize a batch of blue multiresonance (MR)-TADF-conjugated polymers, by grafting an MR-emitting moiety as a pendant onto a conjugated backbone through the unilateral para-carbon position of the nitrogen atom within the MR moiety. These new polymers exhibit blue emissions with PL emission peaks ranging from 459 to 477 nm, accompanied by full width at half-maximum (FWHM) values between 24 and 27 nm. Their electroluminescent devices via solution-processing demonstrate pure blue emissions with a EQEmax of 10.1%, Commission Internationale de I'Eclairage (CIE) coordinates of (0.14, 0.12) and a FWHM of 31 nm, peaking at 462 nm, which demonstrate the best performance among TADF conjugated polymer-based blue organic light-emitting diodes with CIE y values of below 0.15.