Advancing MR-TADF OLED Toward True-Blue CIE Value via Asymmetric Host Materials with Amorphous Morphology
Journal
Advanced Optical Materials
Date Issued
2024-01-01
Author(s)
Han, Chih Pin
Shi, Emily Hsue Chi
Chen, Chieh An
Hsu, Chao Hsien
Chen, Chia Hsun
Wu, Chi Chi
Lee, Yi Ting
Chiu, Tien Lung
Abstract
The new host materials are reported to boost the multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) based pure deep-blue organic light emitting diodes (OLEDs) toward further shortening the emission full width at the half maximum (FWHM). Based on an unusual asymmetric design concept, two new host compounds Bz2cb and Bz2cbz are synthesized. Despite possessing a compact and rigid molecular packing in crystal, Bz2cbz shows pure amorphous morphology via vapor deposition, as confirmed by the grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis. Via incorporating a promising MR-TADF emitter, ν-DABNA-O-Me, into Bz2cb and Bz2cbz films, highly pure deep-blue OLEDs are successfully demonstrated. Remarkably, the Bz2cbz device exhibits a 464 nm electroluminescence (EL) with narrow FWHM of 22 nm, accompanied by the reduction of the 0–1 vibronic sideband, and a maximum external quantum efficiency (EQEmax) of 28.2%, which, overall, reaches the true-blue Commission Internationale de l'Eclairage coordinates (CIE) of (0.13, 0.07) and the high blue index of 253. The amorphous film formation turns out to be an important factor that is previously unrecognized to externally fine-tune the MR-TADF OLEDs toward even higher color purity.
Subjects
host material | multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) | organic light emitting diode (OLED)
Type
journal article