Electroluminescence of polymer/small-molecules heterostructure doped light-emitting diodes

We have successfully fabricated polymer/organic heterostructure doped light-emitting diodes with high stability and efficiency using a novel poly-TPD (PTPD) as hole transport material and the high fluorescent Rubrene as dopant. The basic structure of the heterostructure is PTPD/Alq₃. The device was doped in the single layer and double layer. The structure of energy bands for the doping device was given. Initial voltage, initial luminance, luminance efficiency, EL quantum efficiency and operational stability under constant current driving as well as turn-on voltage were measured. With the doping of double layers, the EL quantum efficiencies are about 2 times greater than that of the undoped device but the turn-on voltage is increased. Comparing the doped device with the undoped device and conventional TPD/Alq₃ diode, it is found that (a) the durability of the devices with PTPD as HTL is higher than that of the referenced device with TPD as HTL, and (b) the stability of the doped devices is significantly higher than that of the undoped device and the lifetime for the device of doped double layers is the longest.