Lasers Create New Materials for Cheaper Solar Cells and LEDs

Lasers Create New Materials for Cheaper Solar Cells and LEDs
Lasers Create New Materials for Cheaper Solar Cells and LEDs

Achieving Cheaper Cells.

Photo-voltaic are very similar to computer chips and light emitting diodes ( LED ) in that they are all based on semi-conductors. The process to make a solar cell shares similarities with micro-chips. For these technologies the process can be very highly automated which helps to produce a cheaper solar cell.

In fact there are not workers needed the most modern robotic factories.

The international prices for solar PV have fallen so dramatically in the last decade. In fact now solar electricity generation from solar PV arrays is almost on par to fossil fuels as far as cost. Much of this cost reduction has come from manufacturers in China. You can argue that Chinese solar manufacturers are dumping solar panels on the market at less than the cost to make them. The reality is that these factories in China are extremely automated and high tech in nature.

ABB Robots are used to manufacture solar cells and modules

ABB Robots are used to manufacture cheaper solar cells and modules

If in fact some countries are dumping solar panels on the market, then the current price is artificial and will likely bounce back up. That is why research in cheaper solar cells using different materials and processes is so important. If we are ever to move away from fossil fuels we will need to continue to lower the costs.

Researchers investigating materials and methods for cheaper solar cells

Researchers investigating materials and methods for cheaper solar cells


 

This is especially true when you consider what has happened to the price of gasoline in the last few years. As automobiles become more efficient and electric cars enter the market. the supply of fossil fuels is out pacing demand. More pressure for renewable electricity to continue to drop.

Techniques for cheaper solar cells.

The most common way to reduce prices of solar cells and modules is to increase the speed and automation of the process. The other way to reduce the price of solar generated electricity from PV is to make the cell itself more efficient and for this researchers around the world are working with new materials and methods.

Materials scientists at Duke University have developed a method to create hybrid thin-film materials that would otherwise be difficult or impossible to make. The technique could be the gateway to new generations of solar cells, light-emitting diodes and photodetectors.

The research team described their methods Dec. 22, 2017 in the journal ACS Energy Letters.

Perovskites are a class of materials that — with the right combination of elements — have a crystalline structure that makes them particularly well-suited for light-based applications. Their ability to absorb light and transfer its energy efficiently makes them a common target for researchers developing new types of solar cells, for example.


The most common used in solar energy today, methylammonium lead iodide (MAPbI3), can convert light to energy just as well as today’s best commercially available solar panels. And it can do it using a fraction of the material which is a sliver 100 times thinner than a typical silicon-based solar cell.

Inside maple

This is an inside look at the RIR-MAPLE technique that has the ability to build new solar cell crystal technology. The white circle at the center of the table is a frozen solution containing the molecular building blocks for the solar cell material, which is blasted by lasers, vaporizing the solution which carries the materials to coat the bottom of the target above.
CREDIT
E. Tomas Barraza

Methylammonium lead iodide is one of the few perovskites that can be created using standard industry production techniques, though it still has issues with scalability and durability. To truly unlock the potential of perovskites, however, new manufacturing methods are needed because the mixture of organic and inorganic molecules in a complex crystalline structure can be difficult to make.

Organic elements are particularly delicate, but are critical to the hybrid material’s ability to absorb and emit light effectively.

“Methylammonium lead iodide has a very simple organic component, yet is a very high-performing light absorber,” said David Mitzi, the Simon Family Professor of Mechanical Engineering and Materials Science at Duke.

If we can find a new manufacturing approach that can build more complex molecular combinations, it will open new realms of chemistry for multi-functional materials.

maple chamber

This is a view inside of the RIR-MAPLE chamber after the thin-film deposition process is over. None of the original frozen solution is left in the center, as it has all been vaporized to coat the bottom of the target hanging above.
CREDIT
E. Tomas Barraza

In the new study, Mitzi teams up with colleague Adrienne Stiff-Roberts, associate professor of electrical and computer engineering at Duke, to demonstrate just such a manufacturing approach. The technique is called Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation, or RIR-MAPLE for short, and was developed by Stiff-Roberts at Duke over the past decade.

Adapted from a technology invented in 1999 called MAPLE, the technique involves freezing a solution containing the molecular building blocks for the perovskite, and then blasting the frozen block with a laser in a vacuum chamber.

When a laser vaporizes a small piece of the frozen target about the size of a dimple on a golf ball, the vapor travels upward in a plume that coats the bottom surface of any object hanging overhead, such as a component in a solar cell. Once enough of the material builds up, the process is stopped and the product is heated to crystallize the molecules and set the thin film in place.

Lasers are used by researchers the world over to find and work with new materials

Lasers are used by researchers the world over to find and work with new materials – credit DLR


In Stiff-Roberts’s version of the technology, the laser’s frequency is specifically tuned to the molecular bonds of the frozen solvent. This causes the solvent to absorb most of the energy, leaving the delicate organics unscathed as they travel to the product surface.

“The RIR-MAPLE technology is extremely gentle on the organic components of the material, much more so than other laser-based techniques,” said Stiff-Roberts.

That also makes it much more efficient, requiring only a small fraction of the organic materials to reach the same final product.

Although no perovskite-based solar cells are yet available on the market, there are a few companies working to commercialize methylammonium lead iodide and other closely related materials. And while the materials made in this study have solar cell efficiencies better than those made with other laser-based technologies, they don’t yet reach those made with traditional solution-based processes.

But Mitzi and Stiff-Roberts say that’s not their goal.

“While solution-based techniques can also be gentle on organics and can make some great hybrid photovoltaic materials, they can’t be used for more complex and poorly soluble organic molecules,” said Stiff-Roberts.

“With this demonstration of the RIR-MAPLE technology, we hope to open a whole new world of materials to the solar cell industry,” continued Mitzi.

We also think these materials could be useful for other applications, such as light-emitting diodes, photodetectors and X-ray detectors.

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