Electroluminescence performance of organic light-emitting devices with KCl inside hole transport layer

A new multilayer organic light-emitting device (OLED) is fabricated by inserting kalium chloride (KCl) thin layer (1nm) into hole transport layer (HTL). It has the configuration of ITO/NPB(15nm)/KCl(1nm)/NPB(25nm)/Alq3(60nm)/KCl(1nm)/Al. The electroluminescence (EL) result shows that the performance of the novel device has obviously improvement compared with the normal structure (ITO/NPB(40nm)/Alq3(60nm)/KCl(1nm)/Al). The EL and efficiency are about 1.4 and 1.3 times than that of conventional device. The suggested mechanism is that the KCl layer in N,N′-diphenyl-N,N′-bis(1-napthyl–phenyl)-1,1′-biphenyl-4,4′-diamine (NPB) can block the holes of NPB and then balance the holes and electrons. The better recombination of holes and electrons is beneficial to the enhancing properties of OLED.