Gallium solar panels can finally progress

Coming from a country where more than two million rooftops have solar panels, the Australian University of New South Wales has been exploring methods to reduce costs to the already cheapest form of electricity generation, and gallium may have given the answer to one of the solar panel's largest drawbacks.

The sun degrades conventional boron-filled silicon.

As one of the most commonly used materials in creating solar panels, direct sunlight on boron silicon reduces its quality in a process known as "light-induced degradation," which has had scientists wracking their brains for over a decade.

In typical silicon solar cells, sunlight is converted to electricity by using it to "break away" negative charges, or electrons, in the silicon, whereas the electrons are collected as electricity.

To allow for efficient generation of energy, impurities are added to the silicon to create a layer with more negative charges than normal silicon (n-type silicon) and a layer with fewer negative charges (p-type silicon).

When the two types are used together, a "p-n junction" is created, allowing a solar cell to operate.

The reason for the degradation is relatively well known. This doping of silicon with impurities allows undesirable elements – such as oxygen, which bonds with boron – to eventually reduce the amount of electricity a solar panel can generate.

Unfortunately, this means that the very sunlight used to generate energy also damages the solar panels over their lifetime. However, gallium appears to be the solution to this problem.

The idea of using gallium as a solar panel life-extending replacement for boron, however, is not new.

For the past 20 years, the process of doping silicon with gallium has been locked under a patent, preventing researchers and manufacturers from exploring this approach. But in May last year, the patents finally expired, allowing the industry to rapidly shift from boron to gallium. In fact, at the start of 2021, leading photovoltaic manufacturer Hanwha Q Cells estimated about 80% of all solar panels manufactured in 2021 used gallium doping rather than boron – a massive transition in such a short time!

As the technology has practically stagnated over two decades, new innovations using gallium are now unlocked for development, allowing UNSW to explore a method called "silicon heterojunction," which has led to the highest efficiency silicon solar cell to date.

In testing this process, the measured voltage of both boron- and gallium-doped solar cells during a light-soaking test for over three days showed that boron solar cells exhibited the traditional degradation, whereas the gallium solar cells maintained higher voltage and stability.

The researchers believe that it may be possible to work at scale with gallium, producing solar cells that are both more stable and potentially cheaper.

Ultimately, it is the prospect of having an entirely new, albeit delayed, venue for study regarding solar renewable energy generation that within the next few years, alongside the ongoing renewable transition, access to cheaper and more efficient energy will be that much easier.