Electropolymerization of Starburst Triarylamines and Their Application to Electrochromism and Electroluminescence

Starburst triarylamines 2 and 3 were electropolymerized to form electrochromic thin films. Film from 2 showed intense absorption at 372 nm before voltage was applied. There were two absorption bands at 496 nm and 1000-2000 nm at 0.3 V, and a broad band, which peaked at 807 nm at 0.6 V. Film from 3 showed intense absorption at 372 nm before voltage was applied. There were two absorption bands at 498 nm and 1000-2000 nm at 0.3 V, and a broad band, which peaked at 890 nm at 0.7 V. The switching time studies revealed that thin film from 2 would require 3 s at 0.46 V for switching absorbance at 1600 nm and 1 s for bleaching. It would also require 4 s at 0.66 V for coloration at 800 nm and 2 s for bleaching. On the other hand, thin film from 3 would require 3 s at 0.46 V for switching absorbance at 1500 nm and 1 s for bleaching. It would also require 3.3 s at 0.76 V for switching absorbance at 900 nm and 1.5 s for bleaching. Electropolymerized thin films of 2 and 3 were also used as the surface modification layers to modify the surface of ITO for polymeric light emitting diode (PLED). To evaluate the performance of the modification layer, we selected a device of ITO/modification layer/PVK-Alq₃-coumarin 6/metal electrode as the standard for comparison. We discovered that co-electropolymerization of the triarylamines 2 or 3 with poly(vinylcarbazole) (PVK) on ITO greatly reduces the turn-on voltage of the PLED devices and their performance is comparable to that of the commercially available PEDOT.