A non-planar pentaphenylbenzene functionalized benzo[2,1,3]thiadiazole derivative as a novel red molecular emitter for non-doped organic light-emitting diodes

A novel non-planar pentaphenylbenzene functionalized benzo[2,1,3] thiadiazole derivative (BPTBTD) has been designed and synthesized with only three steps, and applied into non-doped organic light-emitting diodes (OLEDs) as a red molecular emitter. The molecule exhibits good solubility in common organic solvents, excellent thermal stability and film-forming properties. The most important feature is that photoluminescence of BPTBTD shows excellent stablity in different solvents, at different concentrations and in different solid states. Red organic light-emitting diodes were fabricated in a facile non-doped configuration with different thicknesses of emission layers. Saturated red-emission was observed with an emission peak at 621 nm, a maximum external quantum efficiency of 1.0% and a maximum brightness of 1572 cd m^-2. Especially, the properties of devices with thick emission layers are two times better than those of the devices with thin emission layers. These results indicate that the non-planar pentaphenylphenyl functional groups substantially suppressed the tendency for molecular aggregation in thin solid films, leading to a very stable photoluminescence and higher efficiency of devices with thicker layers.