Improvement of OLED performance by tuning of silver oxide buffer layer composition on silver grid surface using UV-ozone treatment

In this study, silver grid/Ag₂O and AgO_x/MoO₃ transparent conductive electrodes (TCEs) were fabricated and implemented in organic light-emitting diodes (OLEDs). The effects of ultraviolet (UV)-ozone treatment time on the silver grids are discussed. With a treatment duration of 15 s, the Ag₂O thin films do not grow completely and current-voltage characteristics are poor. However, a 30 s UV-ozone treatment yielded good-quality Ag₂O thin films. The Ag₂O thin films were reconverted into the AgO_x phase with further increases in UV-ozone exposure time. The Ag₂O work function is nearly 5.0 eV, which decreases the injection barrier of the silver grids (∼4.7 eV) and MoO₃ (∼5.3 eV). Nevertheless, excessive treatment time leads to the production of AgO_x thin films and an increase in the work function to 5.3 eV, the same as the highest occupied molecular orbital energy of MoO₃, which causes a work function mismatch. The work function mismatch between the Ag grids and the MoO₃ layer results in a high injection barrier, decreasing OLED performance. The electrical properties of the electrodes and devices apparently depend on the composition of the silver oxide buffer layer, as determined using X-ray photoelectron spectroscopy. The surface and optical properties of the TCEs were also investigated. The results show that the OLED devices with the proposed TCEs have better roll off and current efficiency compared to traditional ITO-based devices.