Enhanced electroluminescence from semiconducting polymer blends

We demonstrate the enhancement of electroluminescence (EL) from blends of poly(3-hexylthiophene) (P3HT) in poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylene vinylene) (MEH-PPV). The external EL quantum efficiency η of Ca/P3HT:MEH-PPV/ITO diodes initially increases with P3HT content and goes through a maximum at η = 1.7% photons/electron with only 1 wt.% P3HT; greater than in Ca/MEH-PPV/ITO by a factor of two to three and greater than in Ca/P3HT/ITO by more than three orders of magnitude. At 4 V forward bias, these devices emit signal-red light with brightness of about 220 cd/m2.