How Two Overhyped Materials Could Change Solar Forever

Author: Jon Okun

What if solar panels could generate twice the power for a fraction of the cost, making them cheap enough that you’d actually want them on your roof? Researchers in Australia may have just pulled it off. This is a solar cell made with both perovskites and graphene, the record-breaking result of a collaboration between three Aussie teams: the Queensland University of Technology (QUT), Halocell Energy, and First Graphene. This perovskite cell initially had an efficiency of 16.65%, which is behind the 20% efficiency range of standard silicon.¹ The introduction of graphene, though, almost doubled that initial figure to 30.6% … all while cutting production costs by 80%.²

How is this possible? And more importantly, when might these actually end up on your roof? Well, perovskites have some pretty notable weaknesses, and graphene might be just the thing perovskites need to move forward. The question is, is it feasible for the real world? Both perovskites and graphene have been overhyped for years and tricky to manufacture, let alone manufacture at scale. Can they really solve each others’ problems, or will the financial and engineering challenges keep them benched?

First, let’s back up. What are perovskites, what’s graphene, and why should you care?

We’ve covered perovskites plenty of times before and I’ll link to other videos in the description, so I’ll keep this light and breezy. Perovskites are materials with a crystal structure that lets electrons move freely. This makes them excellent solar absorbers, better than silicon. But they’re fragile. UV rays, heat, and moisture all degrade them, which is a problem when solar panels need to last 20 to 30 years outdoors.³⁴

Silicon, by contrast, is tough and proven. It’s the solar standard for good reason. But it has a hard ceiling at around 30% efficiency.⁵ Perovskites can push past that, if they can survive.

Enter graphene. Again, I’ve touched on this in the past and I’m working on a deeper dive video coming up, so stay tuned for that. Graphene was discovered in 2004, which means it’s barely old enough to legally drink in the US. Despite its youth, it’s strong, lightweight, and highly conductive. Researchers thought it would revolutionize everything.⁶ It hasn’t, mostly because it’s hard to produce pure graphene at scale (that’s starting to change though).

But here’s the thing: graphene’s toughness and water-resistance can protect perovskites from moisture. And combining graphene’s conductivity with perovskites’ efficiency yields impressive results.⁷⁸ So why combine these materials? Because if researchers can make this work, you’re looking at solar panels that could pay for themselves in half the time, survive extreme weather better, and actually make financial sense for the average homeowner. They cover each other’s weaknesses. Graphene protects and enhances perovskites’ performance. Together, they enable manufacturing techniques like the industry-standard roll-to-roll processing that could actually make them viable.⁸

Industry Leaders and Breakthroughs

With that context in mind, let’s take a closer look at the QUT-HaloCell-First Graphene triumvirate. The secret to their success is reportedly using First Graphene’s PureGraph product to add a “layer” to PVs that boosts their conductivity.⁹ The team claims that replacing precious metals with graphene has allowed them to save 80% on material costs.⁹ Again, they maintained those costs while boosting efficiency to that 30.6% benchmark.²

Their graphene pellet additive is made from graphite ore that has a carbon content of over 98%. A proprietary method uses electrochemical exfoliation to produce graphene from graphite. This is already a popular graphene fabrication technique, and it works by applying a voltage to graphite ore. This drives ions into the graphite layers and forces them apart, leaving us with ultra-thin graphene layers.¹⁰ The team claims that the process allows for a graphite-to-graphene conversion rate above 95%.¹⁰ To put that into context, a conversion yield of 65-70% was considered highly efficient even just a few years back.¹¹ ¹² This matters because graphene’s strength has also been its weakness. It’s so tough that integrating it into other systems has been notoriously difficult. If First Graphene’s process makes graphene easier to work with, that’s as important as the efficiency gains.

Proprietary processes always make a me a little skeptical, but I should mention that a 2021 paper in the Turkish Journal of Chemistry did briefly describe a very similar sounding electrochemical exfoliation method. This one uses a sodium hydroxide/hydrogen peroxide/water system that can make “high-quality” graphene nanosheets with the same 95% yield figure.¹³ First Graphene could be using a similar process behind the scenes.

Assuming that these claims are true, an 80% drop in material costs is nothing to sneeze at. It seems that all parties involved are eager to get a competitively priced perovskite-graphene PV on the market. Both Halocell’s perovskites and First Graphene’s PureGraph are compatible with roll-to-roll manufacturing techniques.² This is, more or less, the cheapest and easiest way to a make a PV cell, which should help to further drop costs.

Halocell is currently in the process seeking extra funds to expand its plant in Wagga Wagga, Australia. Earlier this year, that plant began producing commercial perovskite PVs (but not graphene) for use in smaller IoT devices.¹⁴ That’s not as exciting as full-blown PV modules, but it is a verifiable step toward commercialization. The company’s goal is to “eventually“ boost manufacturing up to 60 million perovskite solar cell units annually.¹⁵

Australia isn’t the only place researchers are working to commercialize a graphene-perovskite wombo combo. Actually, if I had a nickel for every time three organizations recently started working together to commercialize graphene-perovskite solar cells… well, then I’d have two nickels.

Swiss company GraphEnergyTech (GET) is teaming up with Taiwan Perovskite Solar Corp (TPSC) and the University of Cambridge. Luckily for me, they have a name for their collective: The Graphene Electrode Technology for Perovskite Solar Cells, or GETPSC.¹⁶

GETPSC’s approach differs from the Australian team. They’re specifically working on swapping out the precious metal electrodes in perovskite cells with graphene. Solar cells typically rely on expensive silver electrodes. This isn’t ideal because silver is expensive, and getting more expensive (expected to reach $50/oz in the next year). Since silver accounts for around 10-15% of your average PV module’s cost, eliminating it doesn’t just help manufacturers … it directly affects what you pay at installation.¹⁷ ¹⁸ Silver electrodes also degrade when in contact with perovskite components.

On top of this, lab versions of PV cells tend to use gold in their electrodes for best results, which isn’t really viable for real-world applications. Graphene, with its super conductivity and durability, already works great as an anode. So, if we can make graphene anodes affordably and at scale, than we can cut costs by a ton.¹⁸

GETPSC is well aware of the difficulties of manufacturing graphene, but the team claims it’s figured out a way to get around that. There aren’t a lot of details, but whatever the method, GETPSC says its electrodes are compatible with scalable manufacturing methods like screen printing, slot-die coating, and inkjet printing, enabling seamless integration within current solar cell production.¹⁶

This particular attempt to commercialize graphene-perovskite cells has garnered some pretty significant funding from outside parties. Innovate UK, a British national R&D agency, recently awarded GETPSC a cool £884,129 (or over $1,176,000). Saudian Arabian oil-giant Aramco also has a hand on the ball. Last year, it invested £1 million ($1.34 million) in the project.¹⁹ GraphEnergyTech’s CEO, Thomas Baumeler, has also mentioned that they’re working on replacing silver electrodes in traditional, silicon heterojunction PVs, too.¹⁶ That could be an interesting area of study to revisit later.

While we’re mostly focusing on attempts to commercialize graphene-perovskite PVs today, research in the field is still ongoing. Just last spring, a team of researchers from the East China University of Science and Technology (ECUST) tackled perovskites’ longevity issue with the aid of graphite. Part of the issue is that perovskites expand by around 1% when exposed to light. This doesn’t sound like much, but repeatedly exposing a perovskite to light, day in and day out, will eventually lead to failure through thermal and physical stresses. At best that will cut into its efficiency, or in the worst case scenario cause outright structural failure.²⁰

The ECUST team needed something ultra-thin and ultra-tough to protect the perovskite from itself. Sounds like a perfect job for graphene! And indeed, they developed a special graphene-polymer “armor” for perovskites. The armor is transparent too, since we don’t want to interrupt the PV processes.²¹ Their tests showed that the graphene armor reduced the expansion rate down to 0.08%. That’s from a tiny amount to next to nothing. Here’s why that matters to you: solar panels are an investment that needs to last 20-30 years to make financial sense. If perovskite panels degrade after just a few years, you’re replacing them before they’ve paid for themselves. The graphene armor extended lifespan to 3,670 hours of continuous operation under simulated real-life conditions, and the cells were still running at 97% efficiency when testing stopped.²¹ The real challenge isn’t just lab endurance, it’s whether these cells can match silicon’s proven 20-30 year performance in real-world outdoor conditions.

According to China Central Television, the ECUST team has begun pilot trials with industry partners.²⁰ Unfortunately, the language barrier means that I’m struggling to find out how those pilot trials are going or who those industry partners might be … so if you happen to know more, let me know in the comments.

MXenes

Graphene is a cool, tiny-layered material, but its not the only one. In fact, a whole bunch of elements like nitrides, transition metal carbides, or carbonites can form fun 2D materials. These all fall under the umbrella of “MXene nanomaterials.” Some of them work a lot like graphene. That’s why researchers from the University of Electronic Science and Technology of China (UESTC) are attempting to make a MXene-perovskite cell that functions just like the graphene-perovskite cells we’ve been talking about.²²

Morphologically, MXene works a lot like graphene by forming a very conductive lattice-like structure. It’s tough, it’s thermally and electronically conductive, and it provides that nice electron highway for fast transfers. So, naturally, it works great with perovskites in a PV capacity. The thinness of MXene allowed the researchers to make a perovskite film that was just 15.2 nanometers. The team claims this thinness translated to an improved surface smoothness in the absorber, which in turn resulted in the formation of super-efficient heat conduction pathways.²² That’s pretty important when heat is one of perovskites’ big killers.

When the team tested their MXene-perovskite cell under standard illumination conditions, they found it had a respectable power conversion efficiency of 25.13%, an open-circuit voltage of 1.177 V, a short-circuit current density of 25.29 mA cm2, and a fill factor of 84.4%. For context, a solar cell without MXene nanosheets achieved values of 23.70%, 1.145 V, 25.18 mA cm2, and 82.2%, respectively. Small but important jumps. The cell also showcased a decent longevity too, retaining almost 80% of its original efficiency after 500 hours.²³

That all said, maybe MXene is a little too much like graphene. The researchers cautioned that big commercial barriers for MXene are its the high cost and complexity. Maybe with more research, MXene will develop its own edge or niche. We’ll have to wait and see.

Reality Check

Clearly, perovskites are making incredible progress. Graphene is making incredible progress. Companies are putting a growing amount time, effort and capital into bringing these technologies to market. It sure feels like it’s matter of time before graphene-perovskite cells are in your hands, but I want to pump the brakes. Despite the rapid advancement of these technologies, there’s still some challenges that will need to be addressed before you start seeing them on store shelves (so to speak).

First and foremost, longevity is still an issue. The various ways researchers have incorporated graphene in these cells is helping. However, “helping” is not the same thing as solving. So, while the cells made by the QUT-HaloCell-and-First Graphene triumvirate are logging impressive lifespans of 153 days … when placed in context next to the 20+ year-lifespans of silicon cells, you can see just how vast of gulf there is between these advanced new cells and good ol’ silicon.²⁴

There’s also a lot of hidden costs when it comes to manufacturing these technologies. Remember, graphene and perovskites are both divas. While companies and universities are in fact successfully developing ways to mass produce them with commonplace fabrication techniques like roll-to-roll processing… this doesn’t eliminate the need to invest in the things that will stop these materials from degrading before you’re even done making the PV. Things like advanced barrier films and protective coatings are all needed to keep moisture, air and light from messing things up. Plus, these are advanced materials: they require some measure of specialized training to manufacture. Advanced training isn’t cheap and it takes time. And as we all know, time is money.²⁵ ²⁶ ²⁷

These issues are all compounded by how young these technologies are. Graphene was only discovered in 2004. Again, it’s barely old enough to drink.⁶ While perovskites have technically been around since the mid 1800s, the first working perovskite PV wasn’t successfully fabricated until 2009!³ As far as my team and I could find, Graphene and perovskites weren’t combined until 2013.²⁸ That means these technologies are very immature compared to silicon PVs, which have been commercially available since the 1950s.²⁹ Plus, silicon works well enough. It’s hitting its theoretical ceiling at 30%, but researchers have found ways around that with multijunction and tandem cells. That represents decades of innovation, optimization and mass production that have all helped to bring down the cost of silicon PV. So, despite the real and rapid improvements in both graphene and perovskite, silicon has a multi-generational head start, and it may well takes decades for graphene-perovskite PVs to reach the kind of maturity and market penetration that silicon has.

Where does that leave perovskites-graphene cells? Looking at where the technology is right now, I’d have say these fall on the lower end of NASA Technological Readiness Level scale — somewhere around 3 or 5.³⁰ We’ve seen some positive tests in simulated environments, especially QUT, HaloCell and First Graphene. They’re creeping up the scale pretty quickly, but there’s no real way of telling when or if they’ll make the leap to commercialization. That makes more sense when you look at the core pieces of tech here. Perovskites have only just had their first commercial deployment last year, courtesy of Oxford PV.

Then again, the technology has advanced pretty quickly in the last few years. I wouldn’t be surprised if we check in next year to find it has hopped a rung or two up the TRL ladder. Graphene manufacturing used to be the major bottleneck, but the claims of these companies are proven, at least to the extent that its now cheaper than the alternatives. This is reflected in the financial forecasts for graphene, which predict huge growth in the next 3 to 8 years, with a predicted compound annual growth rate (CAGR) of 36.5%.³¹ The same thing is true for perovskites,³² with a CAGR of 43.34%. So maybe we won’t have to wait too long. If this tech lives up to even half of its promise, we could be looking at even cheaper, more efficient, and more sustainable solar panels down the road. That’s worth being tentatively, patiently, cautiously… excited about.