Effect of the thickness of Zn(BTZ)2 emitting layer on the electroluminescent spectra of white organic light-emitting diodes

White organic light-emitting diodes (OLEDs) are fabricated with a simple bilayer structure: ITO/TPD/ Zn(BTZ)2/Al. White emission is composed of two parts: one is 470 nm, which originates from exciton emission in Zn(BTZ)2 emitting layer; the other is 580 nm, which originates from exciplexes formation at the interface of TPD and Zn(BTZ)2. Specially, the thickness of Zn(BTZ)2 layer effects the relative intensity of two emissions. When the Zn(BTZ)2 layer becomes thin (or thick), the 470 nm (or 580 nm) emission intensity turns into weak (or strong). Finally, We successfully fabricated pure white OLED when the thickness of Zn(BTZ)2 layer was 65 nm.