Light extraction for a doubly resonant cavity organic LED: the RC~2LED

摘要

The RC~2LED is a substrate emitting OLED which has three additional interference layers between the ITO electrode and the glass substrate. This creates two resonant optical cavities. The RC~2LED has 2 resonant optical cavities. The first cavity is also present in regular devices and is formed by metal/organic layers/ITO. The second cavity is formed by 3 additional layers: a high refractive index layer (Nb_2O_5), a low refractive index layer (SiO_2) and a high refractive index layer (Nb_2O_5). The additional layers introduce a strong wavelength dependent improvement of the extraction efficiency compared to the OLED without the additional layers. Our simulations show an improvement of the extraction efficiency of over 70% over a wavelength range of 75 nm compared to an OLED without the 3 layers. Light extraction is worse compared to the reference OLED for wavelengths outside this wavelength range. This improvement has been experimentally verified for a green OLED with an emission between 500nm and 650 nm. A numerical study shows a relative improvement of 10% for the luminous power efficiency of a 3 color white OLED with the additional layers. The emitted white corresponds with the light emitted by illuminant A. The WOLED has been composed of a fluorescent blue emitter, green and red phosphorescent emitters.