Abstract:
Recently, semiconducting organic materials have attracted considerable-interest-due-to their - potential application in electronics and optoelectronics. Among their . many application fields, electroluminescence (EL) devices using small molar mass organic materials have ' become the. most popular technology that have already been employed in practical , applications such as : flat-- ~ - panel or flexible display devices.1'2 A typical multilayer- (often trilayer) electroluminescent device consists of a light emitting layer, an' electron-transporting ,layer; as., well. as a.: hole: transporting layer. Therefore, the EL performance significantly depends on the recombination efficiency of the holes and electrons injected, from the anode and cathode, respectively. Large efforts are devoted to optimizing the charge flux balance for improving the-device efficiency and limiting the energy consumption, because the hole-transporting material -has a-higher carrier drift than the electron-transporting material in most organic light emitting, diode (OLED) materials.
Bipolar materials with
emission characteristics incorporating
both hole-
and-
electron-.
transporting segments can effectively stabilize exciton formation
and balance
the
hole and
electron charge in the emitting layer.3 6 Moreover, the utilization of bipolar compounds will significantly simplify the device structure with double layers or even a single layer, which will largely limit the overall cost and accelerate its ongoing commercialization activities................
