WP4 Task 2. Ageing

Measurement procedures

 „Natural ageing“

Stable laboratory DC-power supplies are utilized for supplying the operating current or voltage for the devices in the ageing bench. The photometric / radiometric performance of the artefacts, as well as the temperature and current / voltage of the artefacts are monitored.

The electrical and photometric / radiometric performance of each artefact shall be measured after the initial seasoning and after every 2000 h of ageing. Regarding the measurements, the general conditions of IES LM-79 and IEC 62922 apply, unless otherwise specified. The parameters to be measured for each artefact on each measurement round include the following, in this order:

o   Ambient temperature (°C)

o   Relative humidity (% R.H.)

o   Artefact temperature (°C)

o   DC-current (A) and forward voltage (V)

o   Total luminous flux (lm)

o   Relative spectral radiant flux

Chosen artefacts include OLEDs. Due to the possibility of black spots that can form during the operation of OLEDs, the luminance or spectral radiance output of the panels shall be measured for possible changes.

„Accelerated ageing“

An initial seasoning of 100 hours is applied for all products before applying an accelerated ageing stress given below:

·        High Temperature Operating Life test (HTOL);

·        Temperature and humidity stress  (damp-heat);

·        Electrical stress;

·        UV exposure stress.            

It is agreed, that the main output parameters (luminance, luminous flux, colourimetric parameters, voltage, current) will account for the lifetime determination as relative parameters and the operating ageing parameters (current, voltage, junction or board temperature, humidity) will account for the lifetime determination as absolute parameters.