Effect of thermal annealing on the lifetime of polymer light-emitting diodes

Thermal annealing of a polymer light-emitting diode (PLED) is shown to result in a remarkable improvement in the long-term stability of the device. The annealing for such a PLED has to be layer-specific in that the annealing should be carried out for the layer with the lowest glass transition temperature (Tg) to harvest the benefits of annealing. Annealing of this key layer, which is usually the emitting layer, can enhance the thermal stability of the device. The best half-life is obtained at an annealing temperature above the Tg of emitting polymer. It is shown that the annealing of the emitting polymer layer results in a more than an order of magnitude increase in the half-life, in spite of a decrease in the efficiency of the device as the annealing temperature increases.