High Efficiency and Long Lifetime of a Fluorescent Blue-light Emitter Made of a Pyrene Core and Optimized Side Groups.

In this study four emitters of blue light are synthesized by selecting pyrene, with its high photoluminescence quantum yield (PLQY), as the core group and variants of the electron-donating diphenylamine (DPA) as side groups. The four compounds have different numbers, sizes, and substitution positions of alkyl groups on the DPA. Each of the four compounds when doped in OLED devices shows a high current efficiency (CE) of over 7 cd A-1 and a high external quantum efficiency (EQE) of over 7.5%. In addition, the compounds yield electroluminescence (EL) spectra showing peaks with narrow full width at half maximum (FWHM) values of 37-40 nm and hence indicative of high color purity. Moreover, one compound, N1,N6-bis(5-(tert-butyl)-2-methylphenyl)-N1,N6-bis(2,4-dimethylphenyl)pyrene-1,6-diamine (3Me-1Bu-TPPDA), shows a very high EQE of 9.25% and a very long lifetime, with an LT95 of 471 h.