High efficiency warm white phosphorescent organic light emitting devices based on blue light emission from a bipolar mixed-host

摘要

In this study, we demonstrate a high-efficiency and low turn-on voltage warm white phosphorescent organic light emitting devices (PH-WOLEDs) based on a blue mixed-host emission layer (EML) and an orange ultrathin layer. The device has a simple structure and would simplify the fabrication process and reduce fabrication costs. The concept is based on the design a high-efficiency blue mixed-host EML, using an electron-transport material, 4,6-Bis(3,5-di(pyridin-4-yl) phenyl)-2-(3-(pyridin-3-yl) phenyl) pyrimi-dine (B4PYMPM) to enhance the carrier balance ability of the hole-transport material 13-Bis(carbazol-9-yl) benzene (MCP) which operates as the mixed-host and when the MCP: B4PYMPM ratio in the muted-film was 4:1 got better effects. Based on the blue EML, we realized WOLEDs, characterized by a peak power efficiency of 713 Im/W at 3.1 V and a low turn-on voltage of 2.65 V. The muted-host blue EML exhibited a much higher performance compared to the MCP host Stable warm white light emission with Commission International de L'Eclairage (CIE) coordinates from (0.37, 0.45) to (038, 0.47) for a luminance value ranging from 1000 to 10,000 cd/m~2 was obtained.