Bifunctional Group Modulation Strategy Enables MR‐TADF Electroluminescence Toward BT.2020 Green Light Standard

Abstract Herein, a parallel “bifunctional group” modulation method is proposed to achieve controlled modulation of the emission wavelength and full‐width at half‐maximum (FWHM) values. As a result, three proof‐of‐concept emitters, namely DBNDS‐TPh, DBNDS‐DFPh, and DBNDS‐CNPh, are designed and synthesized, with the first functional dibenzo[ b,d ]thiophene unit concurrently reducing the bandgap and elevate their triplet state energy. A second functional group 1 , 1 ′: 3 ′, 1 ″‐ triphenyl , and electron acceptors 1,3‐difluorobenzene and benzonitrile , respectively, to deepen the HOMO and LUMO levels. Accordingly, the CIE coordinates of DBNDS‐TPh, DBNDS‐DFPh, and DBNDS‐CNPh are (0.13, 0.77), (0.14, 0.77), and (0.14, 0.76) respectively, in a dilute toluene solution. This marks the first instance of achieving a CIE y value of 0.77 in dilute toluene solutions. Significantly, the non‐sensitized pure‐green OLEDs based on DBNDS‐TPh and DBNDS‐DFPh demonstrate peak EQE of 35.0% and 34.5%, with corresponding CIE coordinates of (0.18, 0.75), (0.17, 0.76) at the doping concentration of 1 wt.%, representing the first green OLED with a CIE y value reaching 0.76 in a bottom‐emitting device structure as reported in the literature.