Over 2 Years of Outdoor Operational and Storage Stability of ITO-free, Fully Roll-to-Roll Fabricated Polymer Solar Cell Modules

We report on the stability of large-area (100 cm2), low-cost, indium-tin-oxide (ITO)-free modules over two years (>17 500 h) under outdoor operational conditions in Denmark and under indoor storage condition by following ISOS-O-3 and ISOS-D-2 protocols. Irrespective of the testing regimes (storage and outdoor), all modules maintain the maximum power point (MPP) above T80 (the duration over which a solar cell retains above 80 % of its initial MPP) over two years using a simple low-cost packaging barrier with a water vapor transmission rate (WVTR) of 0.04 g m-2 day-1, an oxygen transmission rate (OTR) of 0.01 cm3 m-2 bar-1 day-1, and a UV cut-off at 390 nm. Unlike previous studies, localized degradation through edges and contact points in the modules are not overwhelming even after more than two years; therefore, the differences in degradation under long-term outdoor and storage conditions could be probed. The results suggest that oxygen permeation may be mainly responsible for degradation under outdoor conditions, whereas WVTR has a larger bearing under storage conditions.