High color rending index and high-efficiency white organic light-emitting diodes based on the control of red phosphorescent dye-doped hole transport layer.

We have investigated the transport characteristics of red phosphorescent dye bis(1-(phenyl)isoquinoline) iridium (III) acetylanetonate (Ir(piq)₂acac) doped 4,4',4"-tri(N-carbazolyl)triphenylamine (TCTA), and found that the increasing doping ratio was facilitated to improve the ability of hole transporting. A high color rendering index (CRI) and high-efficiency WOLED was achieved by employing Ir(piq)₂acac doped TCTA film as an effective red emissive layer due to the generation of charge transfer complex (CTC) at the interface. The relative proportion in red: green: blue emission intensity can be controlled by the CTC concentration to obtain high CRI WOLEDs. The WOLED with an optimal red dye doping concentration of 5 wt% exhibits a high CRI of 89 and a power efficiency of 31.2 lm/W and 27.5 lm/W at the initial luminance and 100 cd/m², respectively. The devices show little variation of the Commission Internationale de I'Eclairage coordinates in a wide range of luminance.