Biological Construction of Single‐Walled Carbon Nanotube Electron Transfer Pathways in Dye‐Sensitized Solar Cells

We designed and mass‐produced a versatile protein supramolecule that can be used to manufacture a highly efficient dye‐sensitized solar cell (DSSC). Twelve single‐walled carbon‐nanotube (SWNT)‐binding and titanium‐mineralizing peptides were genetically integrated on a cage‐shaped dodecamer protein (CDT1). A process involving simple mixing of highly conductive SWNTs with CDT1 followed by TiO 2 biomineralization produces a high surface‐area/weight TiO 2 ‐(anatase)‐coated intact SWNT nanocomposite under environmentally friendly conditions. A DSSC with a TiO 2 photoelectrode containing 0.2 wt % of the SWNT–TiO 2 nanocomposite shows a current density improvement by 80 % and a doubling of the photoelectric conversion efficiency. The SWNT–TiO 2 nanocomposite transfers photon‐generated electrons from dye molecules adsorbed on the TiO 2 to the anode electrode swiftly.