Calcium electrodes in polymer LEDs

The qualitative results of a study of the fabrication of Ca/CN-PPV/ITO polymer light-emitting diodes (LEDs) in ultrahigh vacuum (UHV) are reported, where CN-PPV is a cyano-substituted poly(p-phenylenevinylene). If the calcium electrode is deposited on a clean polymer surface under UHV conditions, the device yield is very low, and, for the devices that do function, the electroluminescence lifetimes are extremely short. If the calcium electrode is deposited in the presence of a high partial pressure of oxygen, the diodes are much better in terms of yield, lifetime and luminescence.