Stable white electroluminescence from single fluorene-based copolymers: using fluorenone as the green fluorophore and an iridium complex as the red phosphor on the main chain

Abstract

A series of novel fluorene-based copolymers with fluorenone and an iridium complex on the main chain have been synthesized by Suzuki polycondensation, and characterized by 1H NMR, 13C NMR, and GPC. The TGA results indicate good thermal stability of the copolymers. By incorporating less than 0.15 mol% of both green-emitting fluorenone and red-emitting iridium complex into the copolymers, single copolymers with simultaneous blue-, green- and red-light emission were achieved. Electrochemical study suggests that the fluorenone and iridium complex in the copolymers could function as traps for both electrons and holes. Single-active-layer polymer light emitting devices with the configuration ITO/PEDOT/copolymer/CsF/Al have been fabricated. The device from P3 exhibits a maximum luminance efficiency of 5.50 cd A–1 with CIE coordinates of (0.32, 0.45) and a maximum luminance of 3361 cd m–2. The device from P5 shows a maximum luminance efficiency of 3.25 cd A–1 with color coordinates (0.28, 0.32) and a maximum luminance of 1015 cd m–2. The white light devices based on P4–P6 exhibit low turn-on voltages around 4.0 V, and their CIE coordinates are insensitive to the applied voltages.