Reversible Chemical Reactivity of Non-Fullerene Acceptors for Organic Solar Cells under Acidic and Basic Environment

The chemical stability of non-fullerene acceptors under acidic and basic environments is important because the printable electrodes and interfacial layers are typically acidic (such as PEDOT:PSS) or basic (such as PEI, or amine-stabilized ZnO nanoparticles). In this work, we report a reversible chemical reaction of non-fullerene acceptors (ITIC-family) under acidic and basic environments. OH- anions react as a nucleophile with C=C linkage of the donor and acceptor moieties of ITIC, resulting in a product of ITIC-OH. The reaction breaks the intramolecular charge transfer and destroys the photovoltaic performance. Furthermore, the ITIC-OH can be converted back to ITIC after adding H+. Thus, the non-fullerene acceptors are stable in an acidic environment, but not in a basic environment. This finding provides a guide for the design of interfaces for efficient and stable non-fullerene organic solar cells.