Spin Coating Photoactive Photosystem I–PEDOT:PSS Composite Films

Photosystem I (PSI), a naturally abundant multi-subunit protein complex known for its ability to harvest solar energy and transform it into chemical energy in photosynthesis, is mixed with an intrinsically conducting polymer (ICP) poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) to deposit well-mixed thin films via spin coating from aqueous solution. This process enables uniform, reproducible, and rapid film formation in which the composition and thickness of composite films can be readily tuned up to a few hundred nanometers. We assess the size distributions of the system in solution as well as the composition, thickness, conductivity, scalability, and photoactivity of the resulting biohybrid PSI–polymer films. The combination of the protein and ICP yields increased photocurrents and turnover numbers when compared to single-component films of the protein or ICP alone to reveal a synergistic combination of film components. Based on photocurrents and turnover numbers, the efficiency of integrating the protein with the polymer is highest at low PSI loadings where protein–polymer interactions are maximized.