Improving high efficiency and device lifetime of blue emitters with 3H-benzo[cd]pyrene core and optimized bulky side groups

Abstract

We designed and synthesized two blue fluorescent dopants, N1,N7-bis(4-(tert-butyl)-2,6-dimethylphenyl)-9-isopropyl-5,5-dimethyl-N1,N7-diphenyl-4,5,6a1,11a1-tetrahydro-3H-benzo[cd]pyrene-1,7-diamine (DMP-BP) and N1,N7-bis(dibenzo[b,d]furan-4-yl)-9-isopropyl-N1,N7-bis(4-isopropylphenyl)-5,5-dimethyl-4,5-dihydro-3H-benzo[cd]pyrene-1,7-diamine (DBF-BP), by introducing alkylated N-phenylaniline and alkylated dibenzo[b,d]furan-amine as side groups, based on the pyrene chromophore, 3H-benzo[cd]pyrene (BP) core. When used as dopants in OLED devices, both DMP-BP and DBF-BP exhibited device performances with current efficiencies of over 9 cd A⁻¹ and full width at half maximum (FWHM) values of less than 44 nm. Both materials achieved an excellent device lifetime with LT95 values exceeding 200 hours. Particularly, the DBF-BP device demonstrated a maximum external quantum efficiency of 8.03% and an EL spectrum with a narrow FWHM of 42 nm. The LT₉₅ lifetime of the DBF-BP device was 207 hours, corresponding to an outstanding device lifetime of over 12 000 hours when extrapolated to LT₅₀.