Alleviate microcavity effects in top-emitting white organic light-emitting diodes for achieving broadband and high color rendition emission spectra

It is challenging to obtain broadband emission spectra in top-emitting white organic light-emitting diodes (WOLEDs) due to the well known microcavity effects. In this work, we demonstrate that the microcavity effects can be greatly alleviated by employing a low reflection tri-cathode-layer Yb (5 nm)/Au (15 nm)/MoO3 (35 nm). Top-emitting WOLEDs with evenly separated red, green and blue emission peaks have been achieved. The white emission spectra show weak angle dependence as well. At a luminance of 1000 cd/m2, the top-emitting WOLEDs show an efficiency of 23 cd/A, 10.5 lm/W, a 1931 Commission International de L’Eclairage coordinate of (0.36, 0.42) and a high color rendering index of 85. The top-emitting WOLEDs have been successfully applied in the Si based microdisplay.

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► Microcavity effects have been greatly alleviated by a low reflection cathode.
► The low reflection cathode consist of Yb (5 nm)/Au (15 nm)/MoO3 (35 nm).
► Top-emitting WOLEDs with evenly separated R, G, B peaks have been obtained.
► At 1000 cd/m2, efficiency of 23 cd/A, CIE (0.36, 0.42) and CRI 85 were achieved.
► Top-emitting WOLEDs have been successfully applied in the Si based microdisplay.