Underwater Organic Solar Cells via Selective Removal of Electron Acceptors near the Top Electrode

Electron acceptor degradation of organic solar cells is considered a main contributor to performance instability and a barrier for the commercialization of organic solar cells. Here, we selectively remove the electron acceptors on the surface of donor:acceptor blend films using a tape stripping technique. The near-edge X-ray absorption fine structure (NEXAFS) spectrum reveals that only 6% of the acceptor component is left on the blend film surface after the tape stripping, creating a polymer-rich surface. The optimized morphology avoids direct contact of electron acceptors with the oxygen and water molecules from the film surface. Moreover, the polymer-rich surface dramatically enhances the adhesion between the photoactive layer and the top metal electrode, which prevents delamination of the electrode. Our results finally demonstrate that the selective removal of electron acceptors near the top electrode facilitates the realization of highly durable organic solar cells that can even function under water without encapsulation.