Solar Cells: Too Toxic To Grow – By Michelle Gray

The solar industry, since its inception, has touted creation of a safe, renewable energy solution that would allow the world to stop its dependence on nonrenewable resources such as natural gas, oil and coal. At present, however, many solar manufacturers can reach their end goal only by first hurdling through a noxious and energy-consuming manufacturing process called Chemical Vapor Deposition (CVD).

Volatile, hazardous gases and chemicals are an integral part of the solar cell fabrication process utilizing the storage of gases such as silane and ammonia. Silane is an extremely flammable chemical compound, which loses stability when exposed to air and is listed as a Hazmat 2.1, with 4 being the most dangerous. Tanks of silane have to be stored and transported to solar cell manufacturing facilities. The real danger of silane gas is not its ability to spontaneously combust, but the first explosion and flames won’t occur at the source of the leak. For example, a fire could break out 500 feet from a tank of silane gas that has a leak, and there’d be no indication of a fire at the very source of the fire.

Chemical Vapor Deposition (CVD) is the step in production that requires conversion of noxious gases into an antireflective coating on wafers. A thermal vacuum furnace, running at temperatures of 1,800° F, drawing a tremendous amount of electricity at a dangerously high voltage, is used for the CVD process. So currently in order to conserve oil by using an alternative source like the sun to generate power, it’s necessary to first go through a toxic manufacturing process that uses precious and consumable resources.

Natcore Technology is an R&D company using advancements in nanotechnology research in order to change how the solar industry manufactures solar cells. They have devised a way to replace the CVD step in the manufacturing process with a Liquid Phase Deposition (LPD) process automated through its custom designed wet bench called AR-Box™. This process uses non-toxic, off-the-shelf chemicals in a water based bath at room-temperatures and pressures. Liquid Phase Deposition has benefits on a multitude of levels.

First, any waste that is created during the LPD process can be mixed with water and poured safely down an industrial-grade drainage system. This means Natcore’s waste doesn’t even have a Hazmat rating because it is non-toxic.

Second, Natcore is optimizing a way to recycle 100% of its chemical mixture, thus eliminating all waste, as well as the need for large quantities of water.

Thirdly, the current waste byproduct can be used to make calcium carbonate, a main ingredient in cement manufacturing. If the waste that is generated were used in this fashion it would help an additional industry. In many ways, this is the best form of recycling and aiding in the protection of our planet and its resources.

Lastly, power. Those thermal vacuum furnaces draw nearly 5 times as much power as Natcore’s AR Box™ to put an antireflective coating on the same number of solar cells. To say it another way, Natcore’s technology will reduce the amount of electrical energy required to deposit the AR coating by nearly 80%. That will result in tens of thousands of dollars to hundreds of thousands of dollars of savings per year for a manufacturer using the production version of the AR-Box™.

For example: One full-scale 150 MW production facility would use three furnaces. Natcore’s AR-Box™ would save 1.7 gigawatts of power over the course of a year. In Italy, where electricity is more expensive, it would represent $1.8 million in savings. Something else to consider, that silane gas we talked about earlier, in addition to it being dangerous and noxious, between 50% to 90% of it is actually wasted and has to be disposed of safely.

Natcore’s technology helps reduce the cost in solar manufacturing so that some day it will be feasible to be on everyone’s home. Natcore has spent millions of dollars and several years developing technology that will double the efficiency with a tandem solar cell and cut manufacturing cost in half with the creation of a roll-to-roll flexible solar cell. All the other ecological advantages and cost savings are just an added benefit of their unique technology.

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