A high contrast organic light emitting device employing an emissive organic phase tuning layer

A high contrast-ratio organic light emitting device (OLED) with an emissive phase tuning layer is proposed and experimentally demonstrated. The OLED is implemented by stacking two organic phase tuning layers between composite metal layers of LiF/Al/C₆₀ and LiF/Al and optimizing their thicknesses. Electroluminescence spectrum reveals that the phase tuning layer emits light due to the insertion of ultra-thin C₆₀. Such a tandem device can reduce the operating voltage by 1.1 V, in comparison to conventional high contrast OLEDs. Measured reflection spectra validate the high-contrast capability of the OLED, and demonstrate experimentally an average reflectivity of 6.0% in the visible range from 400 nm to 750 nm, which is much lower than 20.3% for conventional high contrast OLED.