Optical and electroluminescent studies of white-light-emitting copolymers based on poly(9,9-dioctylfluorene) and fluorenone derivatives

A novel type of single white-light-emitting copolymers, PF-DTFOx, derived from poly(9,9-dioctylfluorene) (PF) in which 2,7-di-(2-thienyl)-9-fluorenone (DTFO) is introduced as an orange-emitting unit, is reported, and their application in white-light polymer light-emitting devices (PLEDs) is explored. Because of the very simple structure of DTFO, the synthetic routes to PF-DTFOx are not complicated, and the raw materials are cheap; these are advantageous in reducing the fabrication cost of white-light PLEDs. In the fluorescence spectra, PF-DTFOx in solid powder shows dual peaks at around 460 and 560 nm. In white-light PLEDs, the color of the white-light emission is tunable; this can be achieved by changing the content of DTFO in PF-DTFOx. The light-emission color varies from blue-white to pure white and orange-white when the composition of DTFO increases. All the PLEDs based on PF-DTFOx exhibit maximum luminance above 1800 cd m^-2 and a color rendering index above 80. A class of white-light-emitting copolymers based on polyfluorene is synthesized, in which 2,7-di-(2-thienyl)-9-fluorenone (DTFO) is introduced as the orange-emitting unit. It can be used in white-light organic light-emitting diodes with a single light-emitting layer. The color of the white light can be tuned by changing the content of DTFO.