3,4-Diphenylmaleimide-thiophene-fluorene copolymers for polymeric orange–red light-emitting diodes

Fluorescent copolymers based on 3,4-diphenylmaleimide-thiophene-fluorene triad were newly synthesized and characterized. The copolymers exhibited orange–red fluorescence (λmaxem in the range of 598–620 nm) with fluorescence quantum yields of 32–37% in solution and of 13–22% in solid film. Polymer light-emitting diodes with simple device structure of ITO/PDOT:PSS/copolymers/LiF/Al, where PEDOT:PSS is (poly-ethylenedioxythiophene):poly(styrene sulfonate), were preliminarily fabricated and tested. Similar color to solution photoluminescence, the devices showed orange–red electroluminescence with a maximum electroluminance of 2020 cd/m2 and peak efficiency of 1.25 cd/A.