An iodine-doped polymer light-emitting diode

The performance of polymer light-emitting diodes (LEDs) having the configuration Al/MEH-PPV/ITO, where MEH-PPV=poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene) has been improved by light iodine doping of the emissive MEH-PPV polymer layer whereby the turn-on voltage is reduced and the external quantum efficiency is increased by an order of magnitude. It differs from nondoped MEH-PPV LEDs in that light emission is observed in both forward and reverse bias modes. It is believed that the mobility of the I-3(-) anions in the (MEH-PPV)(x)(+y)(I-3)(xy)(-) species formed on doping the MEH-PPV compensate for injected charges at the electrodes, thus reducing the electron and hole injection barriers. (C) 1997 American Institute of Physics. (C) [S0003-6951(97)00943-1].