Al:SiO thin films for organic light-emitting diodes

Al:SiO cermet thin films were synthesized by thermal coevaporation. Physical properties of these thin films were characterized by scanning electron microscope, transmission electron microscope, x-ray photoelectron spectroscopy, current–voltage, and optical absorption measurement. The data show that the Al:SiO films consist of crystalline Al islands embedded in an amorphous network of mixed Si, $SiO2,$ and $Al2O3$ as Al weight percentage exceeds ∼50%. It is found that the size of Al islands increases with increasing Al concentration, which leads to a dramatic reduction in resisitivity and optical transmittance. A multilayered SiO:Al/Al/LiF structure has been utilized as a cathode for top-emission organic light-emitting diode (TOLED). A model based on Fabry–Pérot cavity has been used to simulate the TOLED light emission spectra. The results indicate that Al:SiO films can also be used as a semitransparent mirror for a half-wavelength planar microcavity light-emitting diode.