Modulating the carrier transport of PtAg2 heteronuclear complexes to attain highly efficient OLEDs with narrow-band emission?

Journal of Materials Chemistry C Pub Date: 2021-03-26 DOI: 10.1039/D1TC00678A

Abstract

High color purity with narrow-band emission is a key factor for full-color displays. However, phosphorescent metal complexes typically exhibit broad emission with a full width at half maxima (FWHM) in the range of 80–100 nm. Here, we demonstrate a facile approach to achieve narrow-band emission by introducing electron-deficient moieties with electron-transport character into PtAg2 heteronuclear complexes. The as-synthesized PtAg2 complex 3 with dibenzo[b,d]thiophene 5,5-dioxide-3-acetylide shows extremely narrow emission with an FWHM of 25 nm in CH2Cl2 solution. The narrow-band emission is further verified by another two PtAg2 complexes containing electron-transport units such as oxadiazole (complex 4) and triphenyl-triazine (complex 5), in which the FWHM values are 26 nm for 4 and 28 nm for 5 in CH2Cl2 solution. TD-DFT studies suggest that the involvement of intra-ligand transition within an electron-deficient acetylide ligand is likely responsible for the narrow-band emission. Solution-processed OLEDs based on complex 4 exhibit excellent device performance with an FWHM of 37 nm in the electroluminescent spectrum and the highest current efficiency (CE) of 69.5 cd A?1, power efficiency (PE) of 50.5 lm W?1 and external quantum efficiency (EQE) of 18.2%. The narrow-band electroluminescence is also attained in complexes 3 and 5 with the FWHM values of 31 and 40 nm, respectively, which represent the narrowest electroluminescence for multinuclear metal complexes. This strategy of introducing electron-transport moieties not only improves the device performance but also narrows the emission width and thus enhances the color purity.

Graphical abstract: Modulating the carrier transport of PtAg2 heteronuclear complexes to attain highly efficient OLEDs with narrow-band emission
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