April 16, 2013, 4:49 PM — In June, Harvard's Clean Energy Project (CEP) plans to release to solar power developers a list of the top 20,000 organic compounds that could be used to make cheap, printable photovoltaic cells (PVCs).
The list, culled from about seven million organic molecules that a crowdsourcing-style project has been crunching over the past two-plus years, could lead to PVCs that cost about as much as paint to cover a one-meter square wall.
"We're in the process of wrapping up our first analysis and releasing all the data very soon," said Alan Aspuru-Guzik, an associate professor of chemistry and chemical biology at Harvard
Today, the most popular PVCs are made of silicon and cost about $5 per wafer to produce. Silicon PVCs have a maximum solar conversion efficiency rate of about 12%, meaning only 12% of the light that hits them is converted to energy.
There is also a small niche market of organic PVC vendors, but their solar cells offer only about 4% to 5% efficiency rate in converting solar rays to energy. In order for a solar product to be competitive, each would need to cost about 50 cents, according to Aspuru-Guzik.
The Clean Energy Project, however, uses the computing resources of IBM's World Community Grid for the computational chemistry to find the best molecules for organic photovoltaics. IBM's World Community Grid allows anyone who owns a computer to install secure, free software that captures the computer's spare power when it is on and idle.
By pooling the surplus processing power of about 6,000 computers around the world, the Clean Energy Project has been able to come up with a list of organic photovoltaics that could be used to create inexpensive solar cells. The computations also look for the best ways to assemble the molecules to make those devices.
Computational chemists typically calculate the potential for photovoltaic efficiency one organic molecule at a time. Over the past few years, computational chemists have identified a few organic compounds with the potential to offer around 10% energy conversion levels.
"But that's only two or three," Aspuru-Guzik said. "Through our project, we've identified 20,000 of them at that level of performance."
In fact, CEP's list of molecules include some that have upwards of 13% solar conversion efficiency rates, Aspuru-Guzik said.
The computing resources from IBM's World Community Grid are split for the CEP. Some of the computers in the grid are making mechanical calculations of molecular crystals, thin films and molecular and polymer blends; others are making electronic structure calculations to determine the relevant optical and electronic transport properties of the molecules.