A systematical investigation in fabrication of white organic light emitting devices (OLED) in combination of fluorescent and phosphorescent materials is reported. In these devices, OXD-7 as blue layer and Ir(MDQ)2acac as a red dopant are doped into host material(s) to make dual-band white OLED. It is discovered that a joint interaction between three components, OXD-7, Alq3 and NPB cause a formation of electroplex in multilayered structure. And a red shift can be observed, which undermines the device performance. This problem can be solved by inserting TDAF as an intermediate layer, which effectively inhibit the electroplex formation and hence eliminate the red shift. Thus, the luminous intensity and efficiency of device are improved.