The invention provides a tool to select reliable organic LED devices,
where the risk for failure before the end of its lifetime is low. This
tool comprises the steps of: i) subjecting the device to a high electric
field over the electroluminescent layer. This leads to a division of the
devices into two, clearly separated, populations, namely one population
with a low leakage current (current through the electroluminescent layer
in reverse voltage operation) and one population with a high leakage
current. In this step, the first population is selected in accordance
with a current criterion. ii) detecting instabilities in the leakage
current, referred to as noise. It has been established that these
instabilities arise in particular at reverse driving voltages between 1
and 10 Volts. These instabilities are a measure of the occurrence of
early failures during operation. In this step, the devices are selected
in accordance with a noise criterion.