Accelerated ageing of organic LED panels using ultraviolet exposure

Abstract

Two different types of commercial organic LED panels were aged with ultraviolet light. One type was aged in an over-filled and open circuit condition with broadband ultraviolet radiation, and the other in an under-filled and closed circuit condition with spectrally dispersed light. Both the luminance values and the spectral power distributions of the panels were measured for both types. The results show that the light output and the spectrum of the panel decay faster when the panels are exposed to ultraviolet radiation when compared to natural ageing. For the panels aged using the under-filled method, the wavelength that reduces the output most is between 320 nm and 340 nm, and the ultraviolet exposure with wavelengths longer than 350 nm did not accelerate the ageing. The ultraviolet radiation exposure increased the ageing by a factor of eight as compared to natural ageing, when the used ultraviolet levels corresponded to one year of exposure on a clear summer day condition. Based on the results, the under-filled method is a valid option for accelerated ageing, especially for studying simultaneously accelerated and natural ageing.