Electroluminescent Polyhedral Oligomeric Silsesquioxane-Based Nanoparticle

A polyhedral oligomeric silsesquioxane (POSS)-based blue light electroluminescent nanoparticle, POSS-FL3, which contains a terfluorene chromophore on each of its eight arms, was easily prepared via the hydrosilation reaction between octakis(dimethylsiloxy)silsesquioxane and an allyl-functionalized terfluorene chromophore that emits blue light as a result of photo- or electroexcitation. POSS-FL3 exhibits good solubility in common organic solvents, such as chloroform, THF, toluene, p -xylene, and chlorobenzene, and good film-forming properties on a quartz plate or an indium tin oxide (ITO) plate; i.e., it has good solution processing properties. The good spectral overlap of the maximum absorption wavelength (391 nm in THF solution) of poly(dihexylfluorene) with the maximum emission wavelengths (394 nm in THF solution) of POSS-FL3 suggests that POSS-FL3 can be used as a dopant of blue light-emissive conjugated polymers such as polyfluorenes to increase their quantum efficiencies through energy transfer. A single-layered electroluminescence (EL) device with the configuration of ITO/PEDOT:PSS/POSS-FL3/Ca (500 nm)/Al (800 nm) was fabricated, with maximum EL peaks at 400, 422, and 464 nm. The external quantum efficiency (EQE) of the POSS-FL3 device (0.0164%) was found to be higher than that of poly(dihexylfluorene) devices in EL devices (0.0095%). Surprisingly, the external quantum efficiencies in EL devices of POSS-FL3 doped poly(dihexylfluorene) blends were found to be about 4−8 times greater than that of poly(dihexylfluorene).