Systematic investigation of transparent organic light-emitting diodes depending on top metal electrode thickness

We investigate the optical characteristics of transparent organic light-emitting diodes (TOLEDs) with thickness variation of the top metal electrode. We find that the thickness variation of the top cathode shows a different influence on the bottom and top side emissions, respectively. The overall efficiency which is the sum of the bottom and top emissions can be enhanced up to 17.7% of external quantum efficiency (EQE) and 25.1 lm/W of power efficiency (PE) at a driving current density of 15 mA/cm2. Furthermore, we carefully investigate the angular distribution of the bottom and top side emissions separately with a spectrogoniometer. We find that both considerably differ from a Lambertian assumption and exhibit opposite trends, depending on the top metal cathode thickness.

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► The optical characteristics of transparent OLEDs are investigated.
► The top electrode thickness variation enhance the overall efficiency.
► The angular distributions of bottom and top side emissions are considerably different from a Lambertian assumption.