Bright red emission from single layer polymer light-emitting devices based on blends of regioregular P3HT and F8BT

Bright red polymer light-emitting devices were fabricated with blends of regioregular poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as an emission layer. The blend films that had more than 10 wt.% P3HT exhibit high device luminance (>10,000 cd/m2) and efficiency (1.8 cd/A), consistent with a relatively large Förster radius for energy transfer from F8BT to P3HT. The emission colour was close to red but with a small orange component (CIE x=0.64, y=0.36). Effective blocking of electrons and excitons by inserting a blocking layer is expected to be necessary to achieve an electroluminescence efficiency commensurate with the photoluminescence quantum efficiency of the blend films (>17%).