High‐Efficiency Stable Flexible Organic Solar Cells with PEDOT:PSS Electrodes via Superacid Fumigation Treatment

Strong acid treatment is regarded as the most effective approach to increase the electrical conductivity of poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) electrodes. However, the conventional soaking treatments of strong acids have drawbacks, including limited flexibility of PEDOT:PSS electrodes coated on thermoplastic underlying substrates, high preparation cost with large acid consumption, and moderate stability of flexible organic solar cells (OSCs). Herein, a unique and cost‐effective fumigation treatment using trifluoromethanesulfonic acid (CF 3 SO 3 H) vapors is proposed. The CF 3 SO 3 H fumigation treatment leads to a highly conductive, smooth, homogeneous, and flexible PEDOT:PSS electrode. On the basis of the CF 3 SO 3 H‐fumigated PEDOT:PSS electrodes, the inverted flexible OSCs yield a high power conversion efficiency (PCE) of 13.62%. Moreover, the flexible solar cells maintain most (≈91%) of the initial efficiency in long‐term storage. This work provides a novel route to make solution‐processed flexible OSCs simultaneously have a high PCE and good storage stability.