Electromechanical reliability of flexible transparent electrodes during and after exposure to acrylic acid

Abstract

The effect of deposition temperature on pulsed laser deposition (PLD) fabricated flexible transparent electrodes subjected to mechanical loading, after exposure to acrylic acid, and the combined effect of fatigue and corrosion on sputter-deposited polyester-based indium tin oxide (ITO) films are both investigated in this study. Acrylic acid containing pressure sensitive adhesives, which are commonly used in various flexible device stacks, can corrode the ITO film. In addition, fatigue due to cyclic loading can lead to film cracking. The combined effect of fatigue and corrosion can lead to catastrophic failure of the system. We found that PLD-produced ITO on polyethylene naphthalate samples deposited at 150°C performs better than samples deposited at 50°C under uniaxial mechanical loading. They were found to exhibit higher crack onset strain than their 50°C counterparts. However, they were observed to be more sensitive to increasing acid concentrations. Scanning electron microscopy images show a larger number of adhesive cracks on the surfaces of the 150°C-deposited samples than the 50°C-deposited samples. Atomic force microscopy results reveal that the increased temperature causes a significant increase in surface roughness which may affect the corrosion behavior of the ITO film.Furthermore, in situ electrical resistance measurements and crack density analysis suggest that the combination of fatigue and corrosion can cause film failure at low strains, less than those needed for failure with no corrosion. For example, at 0.9% applied strain and 500,000cycles, the crack density under fatigue–corrosion is 1.7 times that of the fatigue-only case.