Blue Multiresonance\nThermally Activated Delayed Fluorescence\nConjugated Polymers for Solution-Processable Narrowband Blue Organic\nLight-Emitting Diodes with High Color-Purity

Thermally activated delayed fluorescence\n(TADF) conjugated\npolymers\ngenerally exhibit red-shifted photoluminescence (PL) spectra compared\nto their TADF chromophores, owing to the extension of conjugation\nalong the polymeric backbone. Developing blue TADF-conjugated polymers,\nparticularly those with high color purity, continue to pose a significant\nchallenge. Herein, we design and synthesize a batch of blue multiresonance\n(MR)-TADF-conjugated polymers, by grafting an MR-emitting moiety as\na pendant onto a conjugated backbone through the unilateral <i>para</i>-carbon position of the nitrogen atom within the MR\nmoiety. These new polymers exhibit blue emissions with PL emission\npeaks ranging from 459 to 477 nm, accompanied by full width at half-maximum\n(FWHM) values between 24 and 27 nm. Their electroluminescent devices\nvia solution-processing demonstrate pure blue emissions with a EQE<sub>max</sub> of 10.1%, Commission Internationale de I’Eclairage\n(CIE) coordinates of (0.14, 0.12) and a FWHM of 31 nm, peaking at\n462 nm, which demonstrate the best performance among TADF conjugated\npolymer-based blue organic light-emitting diodes with CIE<sub><i>y</i></sub> values of below 0.15.