Solution-Processable Gradient Red-Emitting π-Conjugated Dendrimers Based on Benzothiadiazole as Core: Synthesis, Characterization, and Device Performances

A family of gradient pi-conjugated dendrimers, in which the 5,5,10,10,15,15-hexahexyltruxene unit is employed as the node, oligo(thienylethynylene)s (OTEs) are employed as light-harvesting branching units, and a 4,7-diaryl-2,1,3-benzothiadiazole is employed as the core, have been developed through the Sonogashira reaction in good yields. All dendrimers were fully characterized by (1)H and (13)C NMR, elemental analysis, and MALDI-TOF MS. Investigation of their steady-state and time-resolved photophysical properties revealed that the gradient dendritic scaffold resulted in efficient energy transfer and strong red emission. On the basis of the good solubility and excellent film forming properties, single-layer red-emitting diodes using these dendrimers as the active materials were fabricated by a simple solution spin-coating process. The moderate device performance was achieved; for example, the maximum luminance of 1290 cd/m(2) with a maximum luminescence efficiency of 1.07 cd/A was performed from BTDyn.