Organic tunable electroluminescent diodes from polyfluorene derivatives

We report on the electroluminescent properties of recently synthesized fluorine-based pi -conjugated polymers. The spectral emission varies from blue to yellow depending on the composition of the alternated copolymers containing thiophene or phenylene moieties. The luminance of the devices can be enhanced by adequate balancing of the hole and electron injection/transport. Incorporation of a hole transporting molecule in the polymer and insertion of an insulating buffer layer in the device resulted in enhancement of the luminous efficiency. A 30-fold enhancement of the luminance was obtained by inserting an electron transporting layer. The highest luminance reached was 1640 cd/m(2) at 17 V and was obtained with a green emitter, poly(2,2 '-(5,5 ' -bithienylene)-2,7-(9,9-dioctylfluorene)) (PBTF). (C) 2001 Elsevier Science B,V, All rights reserved.