Electrical aging mechanism in blue emitting organic light-emitting devices (OLEDs) based on 9,10-bis (2-naphthyl)-2-t-butyl anthracene (TBADN) fluorescent emitter is investigated using a number of techniques, including delayed electroluminescence measurements. The studies reveal that electrical aging is associated with an increasing concentration of an intermolecular species with a weak characteristic luminescence at around 535 nm. This species is capable of charge trapping, and thus plays a role as an electron-hole recombination center with prolonged electrical driving. Weak green luminescence from this species leads to an increased green/blue emission ratio, and causes the color purity loss in aged devices. The results also suggest that this species is also efficient in dissipating excitation energy nonradiatively, hence is capable of quenching TBADN singlet excitons, contributing to the observed efficiency loss with electrical aging.