Microcavity two-unit tandem organic light-emitting devices having a high efficiency

In pursuit of further enhancement in luminance and efficiency of organic light-emitting devices (OLEDs), it is worth exploring what benefits could be obtained by combining two luminance-enhancement techniques, i.e., microcavity and tandem OLEDs. In this letter, we have investigated theoretically and experimentally the characteristics of noncavity and microcavity tandem OLEDs. Results show that with well designed microcavity and device structures (i.e., consistent with resonant and antinode conditions), a fivefold enhancement in luminance can be achieved with cavity tandem devices having only two emitting units. A very high efficiency of 200cd∕A has been demonstrated with a phosphorescent cavity two-unit device.