A systematic study on efficiency enhancements in phosphorescent green, red and blue microcavity organic light emitting devices

The role that microcavities play in the output of an organic light-emitting device (OLED) has now been studied in detail. Chaoyu Xiang and co-workers from the University of Florida in the USA and Yamagata University in Japan investigated the efficiency and spectral characteristics of phosphorescent green, red and blue microcavity OLEDs. They concluded that the luminance output of a device is strongly affected by the reflectivity of its semitransparent electrode and its spectral match to the organic material’s electroluminescence. They fabricated device electrodes from indium-tin-oxide-coated distributed Bragg reflectors comprising two separated stacks of alternating layers of titanium oxide and silicon dioxide. They recorded a luminous efficiency of up 224 cd A–1 for an optimized green microcavity device, with smaller values achieved for blue and red devices.

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