Blue-emitting dendritic molecule with dual functionality as host and dopant for solution-processed white OLEDs with red-emitting material

Abstract

In this study, a three-armed dendritic molecule, 1,3,5-tris(10-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-9,9-diphenyl-9,10-dihydroacridin-2-yl)benzene (3PDPAc), was successfully synthesized and utilized as a blue dopant and its host of two-component white organic light-emitting diodes (WOLEDs). The high molecular weight of dendritic 3PDPAc showed an advantage in the production of rigid thin films with fine surface morphology after doping with red-emitting 7-(7,7-dimethyl-5,13,13-triphenyl-7,13-dihydro-5H-indeno[1,2-b]acridin-2-yl)benzo[c][1,2,5]thiadiazole-4-carbonitrile (IABTCN). Transient photoluminescence spectroscopy confirmed that 3PDPAc and IABTCN displayed conventional fluorescence behavior. Furthermore, it was possible to form a two-component emission layer with 3PDPAc and IABTCN when fabricating a WOLED. The WOLED device bearing 3PDPAc and IABTCN (99.5:0.5 wt. ratio) exhibited 3.80% of the maximum external quantum efficiency (EQE) and CIE coordinates of (0.33, 0.34) which indicates almost pure white emission. The chromaticity of white color emission could be tuned from cool white to warm white by varying the concentration of IABTCN. Moreover, the device with 3PDPAc and IABTCN has been observed to display emission stability because of the miscibility of the host and dopants. Thus, the dendritic structure of 3PDPAc is advantageous for fabrication of a rigid emitting layer.