Abstract
Summary: A strategy to generate an efficient whiteโlight emission has been developed by mixing fluorescence and phosphorescence emission from a single polymer. Fluorene is used as the blueโemissive component, benzothiadiazole (BT) and the iridium complex [(btp)~2~Ir(tmd)] are incorporated into a polyfluorene backbone, respectively, as greenโ and redโemissive chromophores by Suzuki polycondensation. By changing the contents of BT and [(btp)~2~Ir(tmd)] in the polymer, the electroluminescence spectrum from a single polymer can be adjusted to achieve whiteโlight emission. A white polymeric lightโemitting diode (WPLED) with a structure of ITO/PEDOT:PSS/PVK/PFIrR1G03/CsF/Al shows a maximum external quantum efficiency of 3.7% and the maximum luminous efficiency of 3.9 cdโยทโA^โ1^ at the current density of 1.6 mAโยทโcm^โ2^ with the CIE coordinates of (0.33, 0.34). The maximum luminance of 4โ180 cdโยทโm^โ2^ is achieved at the current density of 268 mAโยทโcm^โ2^ with the CIE coordinates of (0.31, 0.32). The whiteโlight emissions from such polymers are stable in the whiteโlight region at all applied voltages, and the electroluminescence efficiencies decline slightly with the increasing current density, thus indicating that the approach of incorporating singlet and triplet species into the polymer backbone is promising for WPLEDs.
Structure of PFIrR1G04 and the EL spectra of its devices under various voltages. Device structure: ITO/PEDOT:PSS/PVK/polymer/CsF/Al.
magnified imageStructure of PFIrR1G04 and the EL spectra of its devices under various voltages. Device structure: ITO/PEDOT:PSS/PVK/polymer/CsF/Al.