High efficiency all phosphorescent white light-emitting diodes based on conjugated polymer host

High efficiency all phosphorescent white electroluminescence was realized by double doping of blue-light-emitting bis(2-(4,6-difluorophenyl)-pyridinato-N,C2′) picolinate (FIrpic) and red iridium complex Ir(DMFPQ)2pbm into conjugated polymer host poly(9,9-dioctylfluorene) (PFO). Effects of hole-transport layer (HTL) on the performances of white polymer light-emitting diodes (WPLEDs) were investigated. First of all, PVK as the HTL was essential, because the back energy transfer from FIrpic to PFO caused by the low-lying triplet energy level of PFO was suppressed by PVK. Furthermore, performances of the WPLEDs were enhanced by introducing CBP into PVK owing to improved balance of electron and hole current. The resulting all phosphorescent WPLEDs have a peak luminous efficiency of 15.5 cd/A and a peak power efficiency of 6 lm/W. Commisssion Internationale de L’Eclairage (CIE) coordinates of (0.41, 0.38) were realized at a current density of 18 mA/cm2. The obtaining of the efficient all phosphorescent white electroluminescence with PFO as host polymer will broaden the approaches of white light generation and be a big promote for the application of phosphorescent WPLEDs.