Excimer emission based on the control of molecular structure and intermolecular interactions

Abstract

Three triple-core chromophore derivatives based on anthracene and pyrene or chrysene moieties, 1,6-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (1,6 DAP-TP), 6,12-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-chrysene (DAC-TP), and 2,7-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (2,7 DAP-TP), were designed and synthesized. For 1,6 DAP-TP, anthracene was attached to the 1,6 positions of pyrene. In the case of DAC-TP, two anthracenes were connected to chrysene, located at the center position within the core, whereas in 2,7 DAP-TP anthracene was connected to the 2,7 positions of pyrene. All three materials had highly twisted core structures and bulky m-terphenyl side groups introduced into the core. Excimer emission was observed in the solid film state and can be interpreted as the result of anisotropic intermolecular alignment (orientation effect). The wavelength of excimer formation was controlled through the change of the center position of the triple-core chromophore, and the color coordinate of white light and efficiency could be controlled when the materials were used in an electroluminescence (EL) device. Excimer EL emissions of 1,6 DAP-TP, DAC-TP, and 2,7 DAP-TP were at 591 nm, 556 nm, and 538 nm, respectively, and CIE coordinate values of the devices were (0.37, 0.31), (0.30, 0.37), and (0.32, 0.44), respectively, showing single molecular white emission. 2,7 DAP-TP showed a white OLED efficiency of 6.01 cd A⁻¹ at 10 mA cm⁻².