For the general public, the word solar is as synonymous with the bulky units on people’s rooftop as it is with the sun. New advances in technology are proving that the manufacture of tiny, efficient solar cell wafers for use in everyday electronics is closer than we think.
There’s a seismic shift happening in the solar industry. The World Economic Forum estimates that the solar power capacity expected to be added in the coming years is equivalent to 70,000 new solar panels every hour. According to the International Energy Association (IEA), photovoltaic solar power grew faster than any fuel in 2016, and there will be far more solar capacity added in the next four years than any other type of renewable energy, including wind and hydropower. But If we’re going to continue this momentum and start developing solar-powered electronic devices—most notably the ones we’re most attached to (our phones)—we must address two problems that exist in the current solar cell manufacturing process.
- The unreliability of the existing processes that use silicon.
- The cost-per-watt of scaling the most efficient semiconductor material available to date: gallium arsenide (GaAs).
Problem #1: Conventional Silicon Solar Cell Manufacturing is Wasteful and Inefficient
The current manufacturing process for solar cells is full of waste and inefficiency. Conventional solar cell manufacturers saw/slice off a thick piece of silicon, leaving behind waste in the form of silicon dust. This byproduct is an environmental and economic burden, and despite the fact that silicon is one of the world’s cheapest and most abundant elements (second only to oxygen), a significant amount of silicon is needed to make up for this loss in the silicon cutting process, which drives up the cost of production significantly. What’s more, a silicon solar cell wafer manufactured specifically for solar electronics must be lightweight, flexible and durable, and it must capture enough energy in low light situations in order for it to be viable for use on the back of your phone. As of today, no such silicon solar cell wafer is available.
Problem #2: Thin-film, GaAs solar cell manufacturing processes are costly
Gallium Arsenide (GaAs) is a semiconductor material and a compound of Gallium and Arsenic. Gallium arsenide solar cells have significant advantages over silicon-based cells. For starters, they are flexible and durable enough to be attached to a portable electronic device like a smartphone or a tablet. It’s also available in a faster, more efficient substrate material than silicon. GaAs is used today in a handful of applications primarily by NASA and the military for satellites, spacecraft, and UAVs, and it produces a far more efficient solar cell when compared to silicon due to an enhanced ability to convert sunlight into electricity. Its band gap is 1.43 eV, ideal for single-junction solar cells. Its absorptivity is so high that it requires only a two-micron thick wafer to absorb sunlight. A panel the size of a phone or a tablet and could add 80 percent to the battery life, can work indoors and outdoors, and can capture energy in low-light conditions, unlike its silicon solar cell counterpart. As you would expect, it can cost about $5,000 to make a wafer of gallium arsenide 8 inches in diameter, versus $5 for a silicon wafer, according to Stanford researchers.
Compounding this issue is that fact that conventional thin-film GaAs solar cells that exist today are manufactured using an epitaxial lift-off technique. While this has helped achieve record-setting solar cell efficiency levels, the process itself is inefficient. At a price of $100 per watt, producing gallium arsenide solar cells is an
Rayton Solar is developing low cost engineered GaAs solar cell wafers
Rayton Solar is a solar cell and engineered wafer manufacturer that is using a proprietary ion implantation technology to make gallium arsenide affordable enough for use in solar powered electronics. Rayton Solar uses advanced particle accelerator technology to develop solar cells consisting of a thin layer of gallium arsenide (GaAs). The company’s approach to manufacturing thin film cells eliminates the need to grow and produce the gallium arsenide material; instead, Rayton can purchase raw ingots to implant and process. Here’s how it works: A proton beam is accelerated and directed into a thin layer of GaAs film where it’s penetrated to a depth of two microns below the surface. The implanted GaAs is bonded, annealed and exfoliated to separate the top layer of GaAs from the ingot. The exfoliated GaAs film is fabricated to create solar cells using standard semiconductor processing including metallization, doping, and anti-reflective coating. By replacing the typical MOCVD production step with Rayton Solar’s ion implantation step, there is a huge reduction in startup costs and cost of overall manufacturing, in addition to an overall reduction in per watt costs to $75/watt.
Gallium Arsenide Solar Cells May Address Our Solar Powered Battery Problem
Behind the cloak of large, colorful screens, processors, and lots of applications, most modern cell phones contain 3-4 grams of Cobalt— the key ingredient used in the lithium-ion batteries that make up the smartphone. In 2018 alone, demand for cobalt could increase 40-50%, with use in the battery sector alone exploding 15-20 fold by 2030. Better battery technology simply hasn’t arrived yet, which means it’s down to software and settings to squeeze out as much out the limited power for as long as possible—or turn to other solutions, such as GaAs.