Mershin's research, which was described in a publicly available paper published in Scientific Reports, builds on a previous project started eight years ago by Shuguang Zhang, associate director at MIT's Center for Biomedical Engineering. Zhang was able to extract tiny structures within plant cells that carry out photosynthesis. He then used chemicals to stabilize the molecules known as photosystem-I to make sure it keeps living and working its photosynthesis magic inside of a solar cell. The green goo, as it's been described, was layered onto a glass substrate where it produced an electric current.
The process Zhang came up with worked. It also required expensive chemicals and the kind of sophisticated lab equipment found only in places like MIT. Not to mention the efficiency of the solar cell was too low to be useful.
Mershin's research made the process simple and cheap, all while boosting the solar cell efficiency by 10,000 percent. Once again, nature provided the inspiration. In Zhang's work, the photosystem-I (or PS-I) was a thin flat layer. Mershin wanted to find a way to expose more of that structure to the sunlight. According to the MIT News Office, he noticed that some pine trees, in addition to the large canopy of branches on top, had a few small branches dotted along the length of the trunk. Those small branches captured any sunlight that managed to get through the massive canopy above. Mershin created a tree-like structure and coated it with PS-1 -- all, of course, on a microscopic scale.
He found a way to create a tiny forest of zinc oxide nanowires (see graphic) and a sponge-like titanium dioxide nanonstructure coated with a light-collecting material from bacteria. The upshot? A supportive structure that carried the electrons generated by the molecules down into material where it could be connected to a circuit. Mershin explains (in simple terms) his research and ultimate goal in the MIT News Office video below.
Despite the improvements, the solar cells are a long way from practical use. The plant-based solar cells only convert 0.1 percent of sunlight to electricity and would need to be improved tenfold or so to be useful, Mershin told the MIT News Office. Still, Mershin believes his dream to bring electricity to the most remote villages is within reach, largely because the process is simplified enough that high school and college labs can begin to replicate and hopefully find ways to improve it.
Mershin hopes that within a few years the solar efficiency will reach 1 or 2 percent, enough to be useful. The only ingredient that would need to be purchased would be a benign, cheap and long-lasting chemical powder that stabilizes the plant waste. The mixture or green goo could then be painted onto any piece of substrate, such as metal or glass, connected by a couple of wires and used to generate enough electricity to charge batteries or provide nighttime light.
[Via: MIT News Office]
Photo: Flickr user pranav, CC 2.0; Video MIT News Office, graphics Scientific Reports