Hyperbranched red light-emitting phosphorescent polymers based on iridium complex as the core

• Published in: Journal of luminescence Vol. 167; pp. 179 - 185
• Main Authors: Guo, Ting, Yu, Lei, Yang, Yong, Li, Yanhu, Tao, Yun, Hou, Qiong, Ying, Lei, Yang, Wei, Wu, Hongbin, Cao, Yong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2015
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2015.06.026

A series of hyperbranched π-conjugated light-emitting polymers containing an iridium complex as the branched core unit and polyfluorene or poly(fluorene-alt-carbazole) as the branched segments were synthesized via a palladium catalyzed Suzuki polymerization. Apparent Förster energy transfer in the photoluminescent spectra as thin films was observed, while no discernible characteristic absorbance and photoluminescence of the iridium complex can be realized in dilute solutions. Copolymers based on poly(fluorene-alt-carbazole) as the branched segments demonstrated enhanced highest occupied molecular orbital energy levels relative to those based on polyfluorene. The electroluminescent spectra of these copolymers exclusively showed the characteristic emission of the iridium complex, with corresponding CIE coordinates of (0.67±0.01, 0.31). All devices exhibited relatively slow roll-off of efficiency, and the best device performance with the maximum luminous efficiency of 5.33cdA−1 was attained by using PFCzTiqIr3 as the emissive layer. These results indicated that the hyperbranched conjugated architectures can be a promising molecular design strategy for efficient electrophosphorescent light-emitting polymers. •Hyperbranched red light-emitting polymers are synthesized.•Red light-emitting iridium complex is used as the branched core unit.•Hyperbranched polymers based on PFCz exhibit higher luminescence.•The highest luminous efficiency of 5.33cdA−1 is attained.