The long-term success of photosynthetic organisms has resulted in their global superabundance, which is sustained by their widespread, continual mass-production of the integral proteins that photocatalyze the chemical processes of natural photosynthesis. Here, a fast, general method to assemble wet and dry solar cells composed of one such photocatalytic protein complex, Photosystem I (PSI), onto a variety of electrode substrates, including gold, nanoporous gold, and graphene is reported. The resulting PSI films consist of a protein matrix that is permeable to electrochemical mediators in a wet cell and conducting for electron transfer in a dry cell. These results demonstrate how the assembly of micron-thick coatings of PSI on non-biological substrates yields a biohybrid ensemble that manifests the photocatalytic activity of the film’s individual protein constituents, and represent signifi cant progress toward affordable, biologically-inspired renewable energy conversion platforms.