Publication date: 8th October 2020
The Photosystem I (PSI) protein complex is known to enhance bioelectrode performance for many liquid-based photoelectrochemical cells. A hydrogel as the electrolyte media allows for simpler fabrication of more robust and practical solar cells in comparison to liquid-based devices. This manuscript reports a natural, gel-based dye-sensitized solar cell that integrates PSI to improve device efficiency. TiO2-coated FTO slides, dyed by blackberry anthocyanin, act as a photoanode while a film of PSI deposited onto copper comprises the photocathode. Ascorbic acid (AscH) and 2,6-dichlorophenolindophenol (DCPIP) are the redox mediator couple inside an agarose hydrogel, enabling PSI to produce excess oxidized species near the cathode to improve device performance. A comparison of performance at low pH and neutral pH was performed to test the pH-dependent properties of the AscH/DCPIP couple. Devices at neutral pH performed better than those at lower pH. The PSI film enhanced photovoltage by 75 mV to a total photovoltage of 0.45 V per device and provided a mediator concentration-dependent photocurrent enhancement over non-PSI devices, reaching an instantaneous power conversion efficiency of 0.30% compared to 0.18% without PSI, a 1.67-fold increase. At steady state, power conversion efficiencies for devices with and without PSI were 0.042% and 0.028%, respectively.
We gratefully acknowledge support from the National Science Foundation (DMR-1507505 and 156014), the NSF Graduate Research Fellowship Program (DGE-1445197 and DGE-1937963), and the U.S. Department of Agriculture (2019-67021-29857). We also thank the Vanderbilt Institute of Nanoscale Science and Engineering (VINSE) for their assistance.