Indenofluorene- and carbazole-based copolymers for blue PLEDs with simultaneous high efficiency and good color purity†
A series of blue-emitting poly(2,8-indenofluorene-co-2,7-carbazole)s, namely P(IF-Cz10), P(IF-Cz25), and P(IF-Cz50), has been designed and synthesized for use in polymer light-emitting diodes (PLEDs). With increasing carbazole content, the resultant copolymers are found to show blue-shifted emission and reduced photoluminescence quantum yields (PLQYs) in films. Consequently, P(IF-Cz25) represents the best trade-off between PLQY and blue light of these materials. The corresponding device reveals a peak external quantum efficiency of 4.12% (3.19 cd A−1, 2.78 lm W−1) and Commission Internationale de L’Eclairage coordinates of (0.150, 0.081). The results clearly indicate that the copolymerization of indenofluorene and carbazole is a promising strategy for developing blue PLEDs with simultaneous high efficiency and good color purity, with a CIEy value of <0.10.