The Metal Intermediate Electrode: A Method to Improve the Current Efficiency of a Tandem Organic Light-Emitting Diode

We prepare a tandem (OLED) with two independent units and three electrodes. One of the units consists of ITO/TPD/Alq₃:DCJTB (5%)/LiF/Al/Au, and the other is Al/Au/TPD/Alq₃/LiF/Al. Two units sharing one transparent intermediate electrode Al/Au, together constitute the entire device. With the same current density, the voltage of the entire device is approximately equal to the sum of two units. The current efficiency of the entire device is several times higher than the sum up of two components. Without directly contacting an external power supply, the bi-metal intermediate electrode has the ability to produce electrons and holes for two adjacent emitting units, respectively. This kind of tandem device is characterized by controllable emission color and higher current efficiency than its two components added up.