Journal Article organic solar cells Polymers stability 3D structure Fullerenes active layer air processing alkoxy side chains all‐photolithography all‐polymer solar cells antioxidant asymmetric solvent transport balanced mobility benzo[1,2-b:4,5-b′]difuran bioinspired blade coating complementary absorption crystallization kinetics donor-acceptor materials gradient covalent organic framework membrane high mobility indoor photovoltaics intramolecular charge transfer effect ion‐gated transistors isomeric solid additives large bandgap polymers mechanical durability medium‐bandgap polymer acceptors morphology stability