Polyviologen as Electron Transport Material in Photosystem I-Based Biophotovoltaic Cells

Abstract

The photosynthetic protein complex, photosystem I (PSI), can be photoexcited with a quantum efficiency approaching unity and can be integrated into solar energy conversion devices as the photoactive electrode. The incorporation of PSI into conducting polymer frameworks allows for improved conductivity and orientational control in the photoactive layer. Polyviologens are a unique class of organic polycationic polymers that can rapidly accept electrons from a primary donor such as photoexcited PSI and subsequently can donate them to a secondary acceptor. Monomeric viologens, such as methyl viologen, have been widely used as diffusible mediators in wet PSI-based photoelectrochemical cells on the basis of their suitable redox potentials for accepting electrons. Polyviologens possess similar electronic properties to their monomers with the added advantage that they can shuttle electrons in the solid state. Depositing polyviologen directly onto a film of PSI protein results in significant photocurrent enhancement, which confirms its role as an electron-transport material. The polymer film not only improves the photocurrent by aiding the electron transfer but also helps preserve the protein film underneath. The composite polymer–PSI assembly enhances the charge-shuttling processes from individual protein molecules within the PSI multilayer, greatly reducing charge-transfer resistances. The resulting PSI-based solid-state platform demonstrates a much higher photocurrent than the corresponding photoelectrochemical cell built using a similar architecture.

Green Catalysts: Applied and Synthetic Photosynthesis

“…Metal NP aggregates, due to the high dielectric constant of the metal, and NP-PSI-NP antenna junctions cause broad-resonant and nonresonant electronic field enhancements, as well as enhancing PSI's light absorption capabilities [13]. Some researchers were able to achieve a 100% quantum efficiency with an integrated photoexcited PSI in solar energy conversion devices as the photoactive electrode [14]. Ag NPs have been found to enhance chlorophyll fluorescence up to 18-fold in peridinin-chlorophyllprotein assemblies, and 5-to 20-fold for thin films of cyanobacterial PSI [15,16].…”

“…Organometallic redox mediators include cobalt-, ruthenium-, and osmium-based complexes typically coordinated by bipyridine ligands. Solid-state electrons can be shuttled and be donated to a secondary acceptor via organic polycationic polymers, such as polyviologens [14]. There are multiple studies utilizing the biological PSI electron donor cyt c6 as well.…”

“…One commonly used class of molecules as diffusible sacrificial electron mediators in PSI-based systems are MV [14]. MV can also be used as a charge carrier for the collection of electrons at the reduced FB PSI site, as it can act as an acceptor of electrons from PSI [48].…”

“…Photoexcited PSI has also been shown to interact with polyviologens in solid state devices. PSI/polyviologen protein surfaces immobilized in Nafion polymer have been shown to significantly enhance photocurrent, aid in electron transfer, stabilize PSI through immobilization, and enhancing electrolyte conductivity [14]. Lower Nafion concentrations have been shown to increase redox mediator diffusivity with both Os(bpy)2Cl2 and MV redox mediators [6].…”

Absorption Analysis of Photosystem I in Different Plants for Biohybrid Solar Cell Applications

“…In each photosystem, the chlorophyll a is the main pigment for photosynthesis and the other supplementary pigments such as chlorophyll b and carotenoid absorb light and transfer the light energy to chlorophyll a. P 680 and P 700 are the critical chlorophyll a with, respectively, maximum absorbance in 680 and 700 nm of light wavelength. [4] PSI and PSII have different applications in photosensor, [5] biophotovoltaic cells, [6,7] and water splitting area. [8] To solve the global warming concerns and increasing the energy consumption demand (anticipated to be 40 TW by 2050), [9] human needs to use a new source of energy like solar cells.…”