We demonstrate high-efficiency organic light-emitting diodes by incorporating a double-emission layer (D-EML) into p-i-n-type cell architecture. The D-EML is comprised of two layers with ambipolar transport characteristics, both doped with the green phosphorescent dye tris(phenylpyridine)iridium. The D-EML system of two bipolar layers leads to an expansion of the exciton generation region. Due to its self-balancing character, accumulation of charge carriers at the outer interfaces is avoided. Thus, a power efficiency of approximately 77 lm∕W and an external quantum efficiency of 19.3% are achieved at 100cd∕m2 with an operating voltage of only 2.65 V. More importantly, the efficiency decays only weakly with increasing brightness, and a power efficiency of 50 lm∕W is still obtained even at 4000cd∕m2.

We report on the fabrication of organic phototransistors based on the spiro-conjugated molecule 2,7-bis-(N,N′-diphenylamino)-2′,7′-bis(biphenyl-4-yl)-9,9′-spirobifluorene. Intramolecular charge transfer leads to an increase in charge carrier density, providing the amplification effect. The sensitivity is better than 1 A/W for ultraviolet light at 370 nm, making the device interesting for sensor applications.

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