Return Of The Bionic Leaf: Plant-Inspired Solar Cell Pushes Efficiency Envelope

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Laboring away in laboratories (hey, why do you think they call ’em laboratories) across the globe, scientists are hot on the trail of a new ultra efficient generation of solar cells based on photosynthesis, a complex series of chemical reactions which any old plant can do with their eyes closed and one hand tied behind their backs. How can human beings beat that? A US research team has just figured out part of the puzzle, so let’s take a look.

A New Ultra Efficient Solar Cell Based On Plants, Part 1.

Before we get over to the new solar cell, anybody here remember that HBO show “The Leftovers?” You know, the one where 10% of the global population suddenly disappears into thin air for no reason? No?

Well then how about the last two Marvel Avengers movies, Infinity Wars and Endgame? Come on, everybody saw those! They raised the bar on mass wipeouts, with 50% of the population disappearing from the entire universe.

That brings us to a real-life case of disappearing, which is more ambitious than The Leftovers though not quite as extreme as Avengers.

Okay, so you probably already guessed that it was the Executive Order signed last Friday night by US President* Donald Trump. One swipe of the pen, and just like that he ordered every federal agency to wipe out 30% of their science advisory committees.

Somebody’s been watching too many movies! Or reruns of old HBO shows! Or both!

A New Ultra Efficient Solar Cell Based On Plants, Part 2.

Where were we? Oh right, the new solar cell breakthrough based on photosynthesis.

The new solar cell is a biological-metallic hybrid, kind of like a bionic man, only a plant. Scientists from the Brookhaven National Laboratory paired up with Stony Brook University on Long Island, New York for the project. BNL’s media office has the explainer:

…scientists from the U.S. Department of Energy’s Brookhaven National Laboratory and Stony Brook University have assembled a nanohybrid structure that contains both biologically derived (biotic) and inorganic (abiotic) materials.

Gee, whiz! What’s it made out of?

They combined a light-harvesting protein from a cyanobacteria, semiconducting nanocrystals (quantum dots), and a two-dimensional (2-D) semiconducting transition metal only one atomic layer thick.

Got all that?  Cyanobacteria (aka blue-green algae) is one of the workhorses of the renewable energy movement, with applications in biofuel and methane conversion as well as solar energy conversion.

The transition metal is molybdenum diselenide, which is another important tool to emerge in the clean tech toolkit.

Quantum dots make up another part of the recipe. These are tiny crystalline particles of semiconductor materials. Also called “artificial atoms,” quantum dots can be tailored at the nanoscale to serve various purposes, like harvesting solar energy.

In the new solar cell, the quantum dots stand in for the light-harvesting protein complex found in plants. They get excited by solar energy, and they transfer that energy over to the APC protein (the one from cyanobacteria). From there it goes to the molybdenum diselenide, which functions as the “reaction center.”

According to the Brookhaven team, the APC layer boosts the efficiency of the solar cell by 30% compared to single-layer molybdenum diselenide, by acting as a sort of funnel.

Onward & Upward For The Bionic Leaf

For more details, look up the paper “Efficient Light Harvesting Biotic–Abiotic Nanohybrid System Incorporating Atomically Thin van der Waals Transition Metal Dichalcogenides” at the journal ACS Photonics.

Next steps for the research include gaining a more detailed insight into the mechanism at work.

That might take a while, so don’t hold your breath for that new hybrid solar cell.

Meanwhile, though, even without the efficiency improvements solar power is getting cheap, cheap, cheaper.

Last month the International Renewable Energy Agency reported that sometime next year, both onshore wind and solar PV will be the least expensive sources of new electricity in many parts of the globe, even without subsidies.

A Day Late & A Dollar Short

All of this sure puts a crimp in President* Trump’s plans for helping the US coal industry out of its doldrums.

The President already tried a couple of maneuvers to keep uneconomical coal power plants up and running in the US but nothing stuck, and renewable energy is beginning to run away with the game ball.

In what appears to be one last Hail Mary, EPA has been working on a rollback of the Obama-era Clean Power Plan.

Good luck with that. The plan got hung up in court and never went into effect, but even without a federal policy wind and solar are still driving coal out of the US power generation market. Natural gas is next on the hit list.

EPA is rolling out the rollback today — for what it’s worth.

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*Developing story.

Photo (cropped): via Brookhaven National Laboratory: Resarchers Mingxing Li (sitting) and Mircea Cotlet (left) of Brookhaven Lab’s Center for Functional Nanomaterials and Jia-Shiang Chen of Stony Brook University’s Materials Science and Chemical Engineering Department.