MAGNESIUM AS ELECTRODE IN POLYMER LEDS

Qualitative studies of the effect of the presence of oxygen during the vapor deposition of magnesium electrodes in the fabrication of single -layer polymer light-emitting diodes (poly-LEDs) in ultrahigh vacuum ( UHV) have been carried out. Using a figure-of-merit based upon yield, intensity and lifetime, the best devices are obtained when fabricated in an essentially oxygen-free environment. The formation of oxides dur ing the magnesium deposition contributes negatively to the charge inje ction characteristics and, therefore, leads to poor poly-LEDs. These r esults, that the poly-LED devices with magnesium as the negative elect rode have the highest performance when fabricated in UHV, are in contr ast to the case of calcium, where fabrication of electrodes is optimum in the presence of about 10(-6) mbar partial pressure of oxygen, as r eported previously.