Enhancement on electroluminescence of OLEDs with high transmittance and low resistance of NiO/ITO composite anode

This paper presents the use of composite NiO/ITO as a transparent conductive anode to enhance the electroluminescence (EL) of organic light-emitting diodes (OLEDs). The work function of NiO/ITO was approximately of 5.1 eV, which falls between that of ITO (4.8 eV) and NPB (5.4 eV). Consequently, the use of a NiO/ITO anode enhanced hole injection, leading to charge balance in the Alq3 emission layer. Hall measurement revealed that the carrier concentration in the NiO/ITO decreased with an increase in NiO thickness, thereby increasing the sheet resistance of the anode. When a 1 nm-thick NiO was deposited on the ITO glass, the mobility of NiO/ITO increased to 30.72 m2 V-1 s-1, compared to 30.61 m2 V-1 s-1 for ITO. As a result, the EL performance of the OLEDs was improved when a 1 nm-thick NiO was deposited. Luminance was enhanced by 33.2%, increasing from 8543 to 11380 cd/m2.