Two peaks observed in the electroluminescence spectra of Alq3-based OLEDs

Tris(8-hydroxyquinolato) aluminum (Alq3)-based organic light-emitting diodes were fabricated with or without using a hole transport layer (HTL). As a conventional device, the ITO/Alq3/Mg-Ag device yielded a green-light emission with a single peak at 525 nm in the electroluminescence (EL) spectrum. In contrast, two sub-peaks were observed in the EL spectrum of some ITO/HTL/Alq3/Mg-Ag devices. This difference was tentatively explained by comparing EL with the photoluminescence (PL) spectrum reported in the literature.