Isomer engineering to adjusting full width at half maximum and emission wavelength for efficient solution-processed red OLEDs

Given the great effect of red dyes with high color purity on ultrahigh-definition displays, exploring new red fluorophores remains urgent. In this work, two novel boron dipyrromethene derivatives (BODIPYs), named o -OMB and p-OMB, were designed and synthesized by adjusting the substitution position of methoxy group. The introduction of tert-butylbenzene units increases steric hindrance and adjacent distance between the host and guest to inhibit adverse Dexter energy transfer. Regioisomerization of methoxy group has a certain impact on photophysical properties, including the distribution of frontier molecular orbitals and recombination energy. The recombination energy of p-OMB is much smaller than that of o-OMB, and the Eg of the former is 1.94 eV less than that of the latter 2.02 eV. Compared with o-OMB, p-OMB with para-substituent has narrower emission spectrum with a FWHM of 37 nm and red-shifted emission wavelength of 634 nm. The solution-processed based -p-OMB OLEDs show a maximum EQE of 1.3% and standard red emission with CIE coordinates of (0.67, 0.33) when using PhCz-4CzTPN as a sensitizer.