VOLTAGE-CONTROLLED 2-COLOR LIGHT-EMITTING ELECTROCHEMICAL-CELLS

A polymer light-emitting electrochemical cell (LEC) is a bipolar p-n j unction device; when biased, a dynamic light-emitting p-n junction is created. In this letter, we report a two color LEC in which the color can be switched by simply reversing the bias voltage. The two color LE C consists of a polymer bilayer structure sandwiched between two elect rodes. In this study, the polymer bilayer consists of a poly(1,4-pheny lene vinylene) (PPV) layer and a poly[2-methoxy-5-(2'-ethylhexyloxy)-1 ,4-phenylene vinylene] (MEH-PPV) layer. When biased at one polarity, t he voltage induced p-n junction is completely inside the PPV layer, an d the LEC emits the green light of PPV. When biased at the opposite po larity, the p-n junction is completely inside the MEH-PPV layer, and t he LEC emits the orange light characteristic of MEH-PPV. (C) 1996 Amer ican Institute of Physics.