Improvement of the Injection and Transport Characteristics of Electrons in Organic Light-Emitting Diodes by Utilizing a NaCl N-Doped Layer

The injection and transport characteristics of electrons are enhanced by using sodium chloride (NaCl) as an n-type dopant doped into a 4,7-diphnenyl-1, 10-phe-nanthroline (Bphen) electron-transporting layer, which improves the performance of organic light-emitting diodes (OLEDs). Meanwhile, a NaCl-doped Bphen layer can effectively influence electrical characteristics of the devices, and significantly improve the current and power efficiency. The turn-on voltage and the operation voltage of the optimal device are decreased drastically from 6.5 V and 10.8 V to 3.3 V and 5 V, respectively, compared with those of the reference device. The maximum current efficiency and power efficiency of the optimal device are 7.0 cd/A and 4.4 lm/W at the current density of 16.70 mA/cm2, which are about 1.7 and 4 times higher than those of the reference device, respectively. Moreover, the enhancement of the injection and transport ability for electrons is attributed not only to the reduced energy barrier between Al cathode and Bphen, but also to the increased mobility of electrons by the doping effect of NaCl. Therefore, both the electron injection and transport ability are enhanced, which improve the carrier balance in OLEDs and lead to the better device efficiency.