Engineered Bacteriorhodopsin Film with Oriented Patterns for the Improvement of the Photoelectric Response

The use of photosensitive proteins has become a competitive solar energy solution, owing to its pollution-free nature, high conversion efficiency, and good biocompatibility. Bacteriorhodopsin (bR) is an important light-sensitive protein that is widely used in the fabrication of photoelectronic devices. However, research on the optimization and comparison of the immobilization techniques is lacking. In this study, in order to obtain bR films with a high energy conversion efficiency, three immobilization techniques, namely dropcasting, electrophoretic sedimentation, and Langmuir-Blodgett deposition, were used to fabricate films, and their topographical and photoelectrical characteristics were compared. All three immobilization techniques can transfer bR molecules to substrates, forming functional photosensitive bR films. The absorption of the bR films at 568 nm reached the highest value of 0.3 under the EPS technique. The peak photocurrent for the EPS technique reached 5.03 nA. In addition, the EPS technique has the highest efficiency factor of 13.46, indicating that it can generate the highest value of photocurrent under the same light conditions, owing to the improved orientation, and no significant decrease in the peak photocurrent was observed after three weeks, which indicates the stability of the photoelectric response. These results indicate that the EPS technique has a great potential for the photoelectrical device fabrication and solar-energy conversion.