Mechanical and environmental durability of roll-to-roll printed silver nanoparticle film using a rapid laser annealing process for flexible electronics

We investigate the mechanical durability and environmental stability of laser annealed silver (Ag) nanoparticle (NP) film. Roll-to-roll printed Ag NP film on polyethylene terephthalate substrate is annealed with a rapid laser annealing process in ambient conditions as an alternative to the conventional thermal annealing process. The laser annealed Ag NP film exhibits superior electrical and mechanical properties, with fast annealing time and no damage on the substrate. The outer/inner bending test results demonstrate that the flexibility of the laser annealed Ag film is excellent. The failure bending radii in the outer/inner bending tests are 3 mm. The laser annealed film can withstand 10,000 bending cycles. A nano-scratch test indicates that the adhesion strength of the laser annealed film is comparable to that of the thermal annealed film. The environmental reliability of Ag NP film is investigated under different high-temperature and high-humidity conditions, while being subjected to cyclic bending fatigue stress. The durability of printed Ag film is found to be influenced by temperature and humidity. The laser annealed film shows relatively large increase in resistance during the bending fatigue test under high temperature and humidity condition (60 °C/90% RH), which is attributed to the oxidation of Ag nanoparticles and initiation of cracks. Generation of cracks is accelerated owing to the combinational effects of the cyclic stress and humidity. These results suggest that, even though the laser annealed Ag film demonstrates sufficient mechanical durability, further improvement of the film properties is required for use in extreme mechanical and environmental conditions.