**3.2. Increasing electron current in IBOLEDs via the combination of two n-doped layers**

The n-doped organic electron acceptors, e.g., n-NTCDA, n-PTCDA, n-C60, possess markedly higher conductivities but markedly lower capabilities of injecting electrons into electron transport layer (such as BCP, Alq3, etc.), as compared to the frequently used n-doped materials (such as n-BCP, n-Alq3, etc.) in OLEDs. However, recent work [13-16] shows that the combination of the above two classes of n-doped materals may increase current in IBOLEDs as described below.
