Organic light-emitting diodes(OLEDs) with a structure of ITO/NPB/Alq3/Al/Ag are prepared.The experimental results show that when Ag is deposited rapidly and the Ag is thicker,the device performance is worse.And when a 200 nm Ag is deposited slowly,the device performance is also poor.However,after inserting a BCP/C60/LiF spacer layer between Alq3 and Al cathode,even if there is 280 nm Ag deposited rapidly,the maximum current density,maximum brightness and maximum current efficiency of the device are still as...