We investigated the luminescence properties of Alq3 in the device structure of ITO/CuPc/TPD/Alq3/Al. The CuPc as a hole-injection material and TPD as hole-transport material. Emission properties were measured by varying a layer thickness of CuPc (0 nm to 50 nm), which is the hole-injection layer. As a result, it was found that the hole injection occurs smoothly when the layer thickness was 20 nm among the thicknesses from 0 nm to 50 nm.
