Simulation of OLED And Its Performance Improvement by Electron Injection Layer Modification

Study of electron injection materials is one of the most important steps in obtaining high efficient and low driving voltage in organic light – emitting diodes (OLEDs). In this article, we simulated OLED devices with structure of ITO/PEDOT:PSS/PH-PPV/EIL/Al in Atlas Silvaco in which, NaSt, Al2O3 and TiO2 are used as electron injection layer (EIL). The OLED with Al2O3 exhibited higher current density, higher luminance (13550 cd/m2), lower driving voltage (2.3V) and lower operating voltage (4.05V) compared to the two other structures. The reason is greater electric field (about 2.4 times greater than that of two other structures) due to much more difference between work function of the device with Al2O3 and electron affinity of PH-PPV, causing improvement of charge carrier injection. Furthermore, recombination almost occurs in the middle of the light emission layer. However, the OLED that employs TiO2 as electron injection layer, showed the highest external efficiency due to increase in radiation recombination rate in comparison with other recombination mechanisms in the light emission layer.