Near-infrared electroluminescence from conjugated polymer/lanthanide porphyrin blends

Abstract

Near-infrared-emitting polymer light-emitting diodes (PLEDs) have been fabricated using blends of conjugated polymers and lanthanide tetraphenylporphyrin complexes. Host polymers include MEH-PPV and a bis-alkoxy-substituted poly(p-phenylene) (PPP–OR11), and the lanthanide complexes include Yb(TPP)acac and Er(TPP)acac (where TPP = 5,10,15,20-tetraphenylporphyrin and acac=acetylacetonate). Electroluminescence (EL) is observed at 977 nm from devices fabricated using MEH-PPV or PPP–OR11 blended with Yb(TPP)acac, and EL is observed at 1560 nm from a device fabricated using a blend of MEH-PPV and Er(TPP)acac. Visible EL from the host polymers is strongly suppressed in all of the devices, however, in the device fabricated using the PPP-OR11 polymer blue emission from the host is completely quenched. Very efficient quenching of the EL from the host in the PPP-OR11 device is believed to occur due to efficient Förster energy transfer, which is facilitated by the excellent spectral overlap between the PPP-OR11 fluorescence and the Soret absorption band of the TPP ligand.