Degradation of Silver Nanowire Transparent Conductors by Module-level Weathering under Electrical Stress

Module-level weathering tests are essential to widen the applications of silver nanowires (AgNWs). In this work, electrical stress is applied to AgNWs in pseudo-module and weathering tests are conducted. The degradation of AgNW network under electrical stress depends on the environmental conditions such as UVA exposure, temperature, and humidity. Nanowire density is a crucial parameter of AgNW network to prolong lifespan of the AgNW transparent conductor (TC). The failure mechanism of AgNW network under weathering test with DC electrical stress includes localized Joule heating, electromigration and photo-induced chemical corrosion. Synergistic effect of DC electrical stress and UVA exposure at elevated temperature results in a narrow break line in the AgNW network perpendicular to the current flow. The conductivity breakdown is caused due to the propagation of the break line as weathering goes on. Under electrical stress, there is no electrical conductivity breakdown in the conditions of UVA exposure at low temperature (40°C in this study) and humid air, because the dominant mechanism of degradation is surface sulfidation of AgNWs. In addition, in a 66.4-day test, there is no degradation with the stressor of electrical stress alone in 40°C dark conditions. Outdoor field test results demonstrate the significance of daily thermal cycle and seasonal humidity. With electrical stress, the failure mechanism of outdoor test is the same as indoor accelerated weathering. Moreover, high humidity coupled with UV and high temperature in the outdoors significantly impair the capping agent of AgNWs, resulting in re-configured morphologies of silver. Systematical and long-term investigation of the outdoor field test of AgNW TCs will be conducted to gain more understanding to the electrical failure mechanism of AgNW network in the outdoor applications.