Photovoltaic devices based on photosynthetic reaction center protein

The electronic coupling between the photoactive proteins and metals are used for the fabrication of hybrid bio-solid-state electrooptical devices. The robust cyanbacterial nano-sized protein-chlorophyll complex photosystem I (PS I) molecules can generate photovoltage of 1 V with absorbed light energy conversion efficiency of 47% (≈23% for solar energy), quantum efficiency of ≈1 are used in photovoltaic devices. Functional oriented junctions were self assembled by covalently binding genetically engineered cysteine mutants of PS I proteins through the formation of sulfide bond with the metal electrode. The dry monolayer generated photovoltage of up to 0.5 V, as measured by KPFM. Using PS I monolayer on gold as a working electrode a sizeable reversible photocurrent was recorded in electrochemical measurements, thus indicating a formation of efficient electronic junction between the protein and the electrode. Placed between metal electrodes and a transparent conducting polymer or glass PS I cells showed a photodiode like response, in preliminary results, recording a sizable photocurrent and voltage. The absorption cross section of the devices can be enhanced by the formation of oriented multilayers. Serially oriented PS I layers were fabricated by the use of nanometric metal junctions formed by autometalization. The metal junctions were used to connect between the outlet and the inlet of electrons in the successive layers. Plasmon enhancement can also be applied to increase the absorption cross section by a formation of an electronic junction between hybrid metal nanoparicles-PS I complexes and metal electrode.