Hybrid-structured indium tin oxide with Ag nanoparticles as crystalline seeds for transparent electrode with enhanced flexibility and its application to organic light emitting diodes

We present highly flexible metal-oxide composite transparent conductive electrodes to apply in flexible organic light emitting diodes (f-OLED). Ag nanoparticle (AgNP) solution were spin coated on polymer substrate to uniformly distribute 50nm diameter AgNPs. With O-2 plasma treatment, oxides formed on AgNPs. Indium tin oxide (ITO) was sputtered on AgNPs-coated substrates. The microstructural analysis by transmission electron microscopy revealed that the ITO on AgNPs grew as domains along (222) that was the mechanically strongest orientation. The rest of ITO around the domains had mixed growth orientations. Decreasing bending radius to 8mm, there was little electrical resistivity change in hybrid transparent conductive electrode (TCE), while ITO on bare polymer became almost insulating by severe cracking. With oxide layers on AgNPs, the optical transmittance of hybrid TCE improved by 7% as the oxides reduced light absorbance. f-OLED was successfully fabricated on hybrid TCE without top-coat, performing better than that on commercial ITO. (C) 2014 The Japan Society of Applied Physics