Bifunctional Group Modulation Strategy Enables MR‐TADF Electroluminescence Toward BT.2020 Green Light Standard
Lin Wu, Ziru Xin, Denghui Liu, Deli Li, Jiasen Zhang, Yubo Zhou, Siyao Wu, Tao Wang, Shi‐Jian Su, Wei Li, Ziyi Ge
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 CIEy 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 CIEy value reaching 0.76 in a bottom-emitting device structure as reported in the literature.