Enhanced performance in organic light-emitting diode by utilizing MoO3-doped C60 as effective hole injection layer

We report an efficient hole injection layer (HIL) composed of MoO3-doped C60 for organic light-emitting diodes (OLED). The structure of the OLED device is ITO/MoO3:C60 (5 nm:5 nm)/NPB (45 nm)/Alq3 (55 nm)/LiF (0.5 nm)/Al. Compared with normal device without a HIL, the device using MoO3-doped C60 as HIL can significantly enhance both hole injection efficiency and electroluminescence. The power efficiency has been increased by approximately 40.7% and 41.7% at the current density of 10 mA/cm2 and 100 mA/cm2, respectively, for the device using MoO3-doped C60 as HIL than the control device. The cause for the enhancement was ascribed to the charge transfer complex formed by co-evaporation of MoO3 and C60. Hole-only devices were fabricated to confirm the hole injection enhancement. Ultraviolet/visible/near-infrared absorption spectra were measured to confirm the formation of the charge transfer complex.