An Effective Approach toward Yellow-to-Orange Multi-Resonance TADF Emitters by Integrating Strong Electron Donor into B/N-Based Polycyclic Architecture: High Performance OLEDs with Nearly 40 EQE

摘要

B/N-based multi-resonance thermally activated delayed fluorescence(MR-TADF) emitters and the corresponding narrow band emissive organiclight-emitting diodes (OLEDs) exhibit great potential for next-generation highresolutiondisplays. Nonetheless, designing MR-TADF emitters with emissionwavelength over 550 nm remains challenging. Herein, an effective approachtoward yellow-to-orange MR-TADF emitters by integrating a strong electrondonatingindolophenazine building block into the B/N-doped polycyclic aromatichydrocarbons is proposed. The investigation of photophysical propertiesreveals that the electron-donating difference between the donor segments ofMR framework has a dramatic influence on the luminescent features, includingthe emission wavelength and full-width at half-maximum (FWHM). TheseTADF emitters display excellent photophysical characteristics such as nearunityphotoluminescence quantum yields and almost 100 horizontal dipoleratio. As a result, yellow and orange OLEDs employing these emitters achievestate-of-the-art device performances with an ultrahigh external quantumefficiency of up to nearly 40, power efficiency of 163 lm W~(?1), and luminanceclose to 120 000 cd m~(?2), which set a record among MR-TADF based OLEDswith emission peaks over 550 nm. More impressively, the fabricated devicepresents outstanding operational stability of LT99 over 110 h at the initialbrightness of 3000 cd m~(?2).