Photogalvanic Effect in Solar Energy Conversion

The photogalvanic effect harnesses photochemical redox processes in a liquid electrolyte to generate and store electrical energy directly from sunlight. In a typical cell, a photosensitiser absorbs photons and enters an excited state, transferring an electron to an acceptor species. A reductant then regenerates the ground‐state sensitiser, completing a closed redox cycle. Unlike conventional photovoltaic devices, photogalvanic cells combine energy conversion with intrinsic storage capacity, offering a dual function that may mitigate intermittency in solar power. Recent advances in low‐cost electrode materials, natural and synthetic sensitiser‐reductant couples, and surfactant‐mediated reaction environments have driven conversion efficiencies and storage lifetimes towards levels compatible with practical applications. Global interest centres on scalable designs, eco-friendly dyes and electrolytes, and integration with off-grid power systems.

Research from Nature Portfolio

Studies have demonstrated the durability and long-term performance of natural extract-based photogalvanic electrolytes. One investigation characterised crude spinach extract as a sensitiser, revealing that its chlorophyll–protein complex retains photogenerative capacity even after extensive illumination and chemical ageing at high pH, with current densities remaining within 20% of initial values after several thousand hours. Another report introduced a novel dye–reductant couple based on Congo red and formaldehyde in an alkaline surfactant medium. Optimisation of surfactant concentration and pH yielded a peak power output exceeding 780 µW, open-circuit potentials over 1 V and a storage half-time of approximately two hours, while elucidating the mechanistic basis for charge separation and back-electron transfer inhibition.

Photogalvanic Effect in Solar Energy Conversion publication trend

The graph below shows the total number of articles in photogalvanic effect in solar energy conversion across all publications each year (not limited to Nature Index journals).

Technical terms

Photogalvanic effect: Generation of electrical current through light-induced redox reactions in an electrolyte cell.

Photosensitiser: Molecule that absorbs photons and initiates electron transfer in a photogalvanic cell.

Reductant: Chemical species that donates electrons to regenerate the ground-state photosensitiser.

Conversion efficiency: Ratio of electrical energy output to incident light energy.

Open-circuit voltage: Maximum voltage across the cell when no external load is connected.

Short-circuit current: Current measured when the cell’s terminals are directly connected with negligible resistance.

Storage capacity (t₀.₅): Time required for the cell’s stored energy output to decay to half its initial value in the dark.

Surfactant: Amphiphilic additive that improves dye dispersion and accelerates interfacial electron transfer.

References

1. Graphite counter electrode modified Tropaeolin‐O photo‐sensitized photogalvanic cells for solar power and storage. EcoEnergy (2024).
2. Increasing photogalvanic solar power generation and storage capacity of brilliant cresyl blue by employing surfactant and natural sunlight. Battery Energy (2024).
3. Simultaneous electrochemical solar power generation and storage using metanil yellow-formic acid as a new sensitizer-reductant couple in photogalvanic cells. RSC Advances (2019).
4. Use of Congo red dye-formaldehyde as a new sensitizer-reductant couple for enhanced simultaneous solar energy conversion and storage by photogalvanic cells at the low and artificial sun intensity. Scientific Reports (2020).
5. Characterization, stability, and feasibility of long-term use of light-absorbing components of aqueous spinach extract-based photogalvanic electrolyte. Scientific Reports (2022).