Chlorophyll-based Bio-Photovoltaic Cells

Robert Murray-Smith. 2014. Making a Solar Cell from a Leaf. Video. Retrieved from

  • 0:32–1:46: On its use of Cu and Al strips and an electrolyte-impregnated paper towel, and how it's not a battery despite this arrangement; to demonstrate this, a version with significantly larger electrodes was constructed that sandwiched the electrolyte (in a way that left no part of it exposed to light), and which showed 0uA
  • 1:50–: In contrast, the 'solar cell' version / geometry (which had an active area of, perhaps, 20cm2) produces 40–50uA under (ambient) fluorescent lighting, even after three days
  • 2:44–3:32: On the lack of corrosion of the electrodes, and the use of disparate metals to provide some 'current direction'. “But we're getting constant supplies of small amounts [of current] from that structure, where we've got leaf extract between two different metals. I used these two different metals to do a bit of current direction. If you have two same metals then you still get an output from it, but the output is much, much lower because, I think, the electrons don't know where to go. And in this setup, they know where to go, so you get a much better capture of it.”
  • 3:46–4:33: A rather unconvincing demonstration of its increased output under direct exposure to a halogen light. (Spoilers: it didn't seem to make a difference, at least within the few seconds that the exposures were changed.)

Robert Murray-Smith. 2014. Making a Solar Cell from a Leaf: Extracting Chlorophyll into a Deep Eutectic Solvent. Video. Retrieved from

In this video, approx. 10g of birch leaves are placed into 250mL of deionised water and blended for 20 mins; the resulting liquid is double-vacuum filtered. The resulting filtrate will ultimately be added to a deep eutectic solvent made from a 2:1 (molar ratio) mixture of Mono-ethylene(?) glycol and (?) chloride. (The chemical names were not clear from the audio, but the molecular masses were given as 62 and 139g/mol, respectively, suggesting they are, in fact, Ethylene glycol (62.07g/mol and Choline chloride (139.6g/mol).)

To prepare the solvent, the mixture needs to be heated to approx. 80°C (whereupon its consistency will change from that of a more sugary molasses to a liquid). This is then mixed, 1:1 with the chlorophyll extract, and kept at approx. 95°C until its volume has reduced back down to a single unit of volume, by which time virtually all of the water will have evaporated (given the much higher boiling points of the other solvents).

Robert Murray-Smith. 2014. Solar Cell from a Leaf: Update. Video. Retrieved from

In this video, an electrolyte made with twice the starting leaf material is presented, and shown to produce ~75uA (compared to ~40uA from an equally-sized 20cm2 cell); its response upon exposure to a halogen light is also noticeably quicker.

“What that's suggesting to me, and should be suggesting to you, I guess, is that it's the chlorophyll that's actually responsible for the effect that we're seeing.”

Robert Murray-Smith. 2014. Working on the Leaf Based Solar Cell: A Lab Log. Video. Retrieved from

The design, as shown at the end of the video, was reported to produce approx. 0.5W/sqm. While still a lot less than the approx. 30 to 50W/sqm that is typically produced by commercial silicon-based PV cells under real-world situations, this is also much better than the 1.2mW/sqm generated by Copper(I) oxide-based cells. And, when the environmental and financial costs of production (and the feasibility of refurbishment) are taken into account, this type of cell becomes even more interesting.


Robert Murray-Smith. 2014. Solar Cell from a Leaf Update: In The Sun. Video. Retrieved from

Robert Murray-Smith. 2014. Solar Cell from a Leaf: Review and Direction. Video. Retrieved from

  1. Exactly why does this work the way it does? (Note to self: look into the liberation / use of electrons in plant-based light-dependent reactions; e.g., see this)
  2. Could algae be used instead (as they're almost entirely chlorophyll, at least when compared to leaves)?
  3. How quickly does chlorophyll degrade / decompose? Given that it's not actually alive (rather an organic compound produced by living organisms), can it be sterilised (in a way that doesn't break it down) to extend its useful lifespan?
  • Last modified: 2022-05-28 21:32
  • by Peter