An organic p–n junction as an efficient and cathode independent electron injection layer for flexible inverted organic light emitting diodes

We demonstrate an organic p–n junction as an efficient electron injection layer for green inverted bottom-emission organic light emitting diodes (IBOLEDs). The organic p–n junction composed of a p-CuPc/n-Bphen layer showed very efficient charge generation under a reverse bias reaching to 100 mA/cm2 at 0.3 V, and efficient electron injection from indium tin oxide (ITO) when adopted in IBOLEDs. Moreover, the organic p–n junction resulted in the same current density–voltage–luminance characteristics independent of the work function of the cathode, which is a valuable advantage for flexible displays.

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► Organic p–n junction is used as an efficient and cathode independent electron injection layer.
► Electron injection characteristics of p–n junction are independent of EF of electrodes.
► The new pn-i-p inverted OLEDs showed good performance, regardless of the electrodes.