Micro-Transfer Printing for Solar Cells

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According to experts, micro-transfer printing is the way to go if you’re working with non-native substrates and want to assemble microscale semiconductor devices.

The process of micro-transfer printing involves bringing together a precision motion controller and an engineered elastomer stamp in order to register and allocate a range of microscale devices.

Micro-transfer printing can be done on a number of devices and materials. For example, it has been applied to Gallium Arsenide solar cells, Gallium Arsenide LEDs, Gallium Nitride LEDs, Gallium Arsenide lasers and even Silicon integrated circuits.

You need to have a really small and thin device that measures < 10 microns and has < 100um lateral dimension. This is so you can get wafer-level heterogeneous integration and compatibility with different device formats.

How Does It Work on Solar Cells?

Solar Cells

Micro-transfer printing was initially used to print flexible electronics. Since then, it has played a pivotal role in the way engineers concentrate on solar technology, especially at tech startups.

Although many tech startups are known for producing tiny solar cells that are the size of a ballpoint pen dot, they have been endorsed by the National Renewable Energy Laboratory as being able to have solar energy to electricity yield rate of 41%.

Brand-new production plants will be dedicated to the manufacture of concentrating solar arrays. The great thing about these solar arrays is that they’ll be produced using the micro-transfer printing technique.

The semiconductor printing technology is useful for a number of other applications, from improving the performance of LED lighting, medical device sensors, and hard drives.

In the meantime, the other production facilities will continue to focus on building a cutting-edge concentrating photovoltaic (CPV) collector. This particular collector has tiny solar cells that are able to concentrate 1,000 times more light.

The Benefits of Tiny Solar Cells

Tiny Solar Cells

The whole point of the focus on tiny solar cells is that they can reduce the cost of concentrating solar power, especially in sunny areas that are located in places like the southwest U.S.

In order to build a solar array made from microcells, a machine is used to build a small semiconductor upon a substrate.

Those cells are then transferred to a wafer through the same machine. The end result is usually a triple-junction solar cell that’s very efficient due to the layers that are spontaneously added to the wafer.

This process is so simple that it makes it possible to print thousands of cells at a time onto the wafer.

The machinery can also be used in conjunction with other semiconductor materials such as silicon and gallium arsenide.

According to NREL’s CPV applications engineering manager Kanchan Ghosal, the technique uses micro-cells as well as transfer printing to condense the number of materials that are required to create concentrated PV modules.

This makes it a great alternative to the usual manufacturing method. There are big plans for the future which include expanding the production capacity in order to create a system that’s able to produce viable electricity at just 10 cents or less per kilowatt-hour.

Normal CPV arrays use optics and mirrors to reflect light hundreds of times onto highly proficient triple-junction cells. They mount these onto trackers so that they’re able to get as much sunlight exposure as possible.

Mounting them at an angle also improves their performance. However, this improved performance does come at a cost due to the trackers and optics.

So far, flat solar panels are the most used for both residential and commercial applications while only a few CPV systems have been constructed.

However, the outlook for CPV technology is largely positive, as the market for it is expected to double and develop into a 10-gigawatt industry by the year 2020.

The Department of Energy was responsible for the initial funding when the technology was first developed many years ago.

Meanwhile, the State of North Carolina is expected to build and open a production plant that will have a solar panel production capacity of 5 megawatts.

NREL reports that the state has partnered with local agencies to finance the construction of the plant to the tune of $7.9 million.

How Tiny Solar Panels Can Power the Internet of Things?

Tiny Solar Panels

The Internet of Things (IoT) refers to a phenomenon of hyper-interconnectivity that forms a global network of objects. These objects will be responsible for practically running our lives.

Truth be told, IoT is already in full swing, as we have devices that are responsible for running SMART homes, self-driving cars, and even gadgets that monitor our health.

However, in order for the IoT to become a global reality by the projected time frame (2020), these smart sensors need to have a reliable source of power.

They could use mains electricity in a way similar to traffic light sensors, but this could be tricky due to the complexity of how these new sensors operate.

Energy experts recommend the use of organic solar panels because they’re affordable, and can power sensors of all shapes and sizes, even the tiny ones.

Although these cells have microscopic dimensions of two micrometres, they need a lot of power so that they can absorb bucket-loads of light at a time.

The difference between organic photovoltaics (OPVs) and silicon solar cells is the fact that specially-synthesized organic materials have to be used in order to construct the former.

This makes for a very cost-effective production process which involves PET and other cheap substrates. This makes the end product much more flexible and significantly lighter.

It also means that the consumer will now have more colour options than before, instead of settling for the usual plain black solar cells. The energy payback time of OPVs is an impressive 24 hours.

This means that the energy which was put into their products can be earned back in just one day.

Another benefit of organic photovoltaics is the fact that they can be shaped onto 3-D surfaces like clothes and even roof tiles. This particular feature makes them suitable for catching slanting or diffuse light and makes them ideal even for areas that experience cloud cover.

While these improvements may not seem like much right now, they’re expected to literally change the way the IoT works. Most of these sensors will be placed in less than ideal locations that wouldn’t normally allow for optimal energy harvesting.

These small organic solar cells will allow for on-going energy harvesting regardless of where they’re placed, whether they’re sewn onto clothing or placed indoors or in cloudy areas.