Near-Infrared Emission from Organic Light-Emitting Diodes Based on Copper Phthalocyanine with a Periodically Arranged Alq₃:CuPc/DCM Multilayer structure

We demonstrate near-infrared organic light-emitting devices with a periodically arranged tris(8-quinolinolato)alumi-num (Alq₃):copper phthalocyanine (CuPc)/4-(dicyanomethylene)-2-methyl% -6-(4-dimethylaminost-yry)-4H-pyran (DCM) multilayer structure. DCM and Alq₃ doped with CuPc were periodically deposited. Room-temperature electrophosphorescence was observed at about 1.1μm due to transitions from the first excited triplet state to the singlet ground state (T₁-S₀) of CuPc. In this device, we utilize the overlap between the Q band π-π* at about 625nm of the absorption spectra of CuPc and the PL spectra of the DCM. The near-infrared emission intensity of the CuPc-doped Alq₃ device with DCM increases about 2.5 times larger than that of the device without DCM. We attribute the efficiency enhancement to the better overlap between the PL spectra of DCM and the absorption spectra of CuPc.