A simple method for the photometric characterization of organic light-emitting diodes

A simple method for the photometric characterization of organic light-emitting diodes (OLEDs) is reported. It is based on the indirect measurement of the total emitted optical power by using a calibrated photodiode and the optical emission spectrum and space emission diagram of the OLED. From this and by measuring the current–voltage characteristic of the OLED all the relevant radiometric and photometric quantities can be extracted, including the external quantum efficiency. The usual method to collect all photons emitted by a LED source in the half space uses an integrating sphere with the LED source placed at the entrance hole and a photodiode (PD) placed at an exit hole at some point on the sphere surface. Here we show that the same result can be also achieved in free space by a simple geometrical arrangement of the PD in respect of the OLED source, with no need of an integrating sphere. Moreover, we find that a large area photodiode placed in contact with the OLED surface measure about 82% of the total emitted power.