Will tandem solar be deployed at gigawatt scale by 2022? Would you take that bet?

Last year, Frank van Mierlo, the CEO of solar silicon company 1366 Technologies, bet this reporter that ​“the solar market will see 2 gigawatts of tandem solar in the marketplace by the end of 2022.”

In a transparent effort to win this bet, van Mierlo just merged his direct silicon wafer company with Hunt Perovskite Technologies. The newly formed company, CubicPV, will use HPT’s printed perovskite process combined with 1366’s silicon process to manufacture tandem photovoltaic modules, with the ultimate aim of making higher-efficiency solar panels.

CubicPV, which is now helmed by van Mierlo, just raised $25 million from Hunt Energy Enterprises, First Solar, Breakthrough Energy Ventures, North Bridge Venture Partners and Polaris Partners. This is in addition to the more than $100 million raised by 1366 over the last decade.

Ever higher solar efficiency

Solar panels with higher efficiencies mean greater electricity production, less land use and lower costs for zero-emission power. The promise of higher-efficiency solar has attracted tens of billions of dollars in venture and corporate funding over the last decade.

High-quality solar modules on the market today have efficiencies of 21 percent to 22 percent. Commercial crystalline silicon is forecast to reach efficiencies of 22 percent to 24 percent by the end of the decade, and possibly higher if interdigitated back-contact heterojunction products get to market.

A tandem solar panel combines two photovoltaic materials in a single panel and could potentially break through the efficiency barrier of single-junction silicon because of the different wavelength ranges of silicon and perovskite materials. The practical limit for tandem module efficiency is 30 percent, according to van Mierlo.

A tandem solar structure can be created by depositing a photovoltaic material on a photovoltaic substrate or mechanically stacking two photovoltaic materials. The National Renewable Energy Laboratory has been researching the technology for years, but recent technology gains in photovoltaic perovskite materials have accelerated the development of tandem modules. 

Last year, van Mierlo said that tandem modules combining high- and low-bandgap material are ​“the most important innovation in solar since solar was first conceived in Bell Labs in 1954.” 

A wager

Last year, when I asked van Mierlo about his company’s shift from silicon wafer technology to tandem technology and aired my concerns about this technology path, the CEO suggested we embark on a small wager on tandem’s commercial future, with one bottle of fine champagne going to the winner.

He is betting that tandem will soon become a significant part of the solar market and believes that 2 gigawatts of commercial tandem solar will be sold worldwide by the end of next year.

He went even further, writing last year, ​“In fact, not only do I believe that multiple gigawatts of tandem will be sold before the end of 2022, but I am also confident that in a decade’s time, tandem will command more than 50 percent of our industry’s market share.”

The current figure is zero percent.

In the interest of mercy, I urge van Mierlo to save face by conceding now and, in lieu of that champagne, making a meaningful donation to Canary Media to support fierce, independent journalism on the energy transition. (It’s tax-deductible; we’re a 501(c)(3).)

I win this bet

Perovskites have the potential for high efficiency and low cost, but we won’t see gigawatts of tandem cells anytime soon because of a number of factors, including:

• Reliability. Moisture and oxygen make a perovskite solar cell act more like a fuse than a diode after hundreds or thousands of hours of use. On the other hand, silicon is the most studied element in the periodic table, and more than 100 gigawatts of the stuff will be deployed in PV applications around the world this year. We know silicon’s failure modes and its long-term behavior. It will take years to gain confidence in the long-term reliability of a new materials system or tandem combination and to understand failure modes and degradation paths. Hunt Perovskite Technologies, now merged into 1366, does claim to be developing ​“stable and efficient” metal halide perovskite materials for the utility-scale market. (For more on utility-scale solar, see Canary’s inaugural Solar High Rollers column.)
• Developers, banks and underwriters. A solar project is an investment tool that turns photons into kilowatt-hours and dollars — and the extremely risk-averse financial community does not tolerate new and unproven technologies. Greater risk in any aspect of a solar project translates to nervous underwriters, a higher cost of capital and an uncompetitive project.
• History is on my side. The road is littered with the remains of hundreds of solar aspirants, all keen to commercialize some alternative to straight-up crystalline silicon, whether amorphous silicon, CIGS, CdTe or GaAs. Not one company, other than First Solar, has been able to succeed commercially in this effort.

The perovskite contenders

In addition to CubicPV, other tandem and perovskite solar startups are angling for share in this market:

• BlueDot Photonics uses ​“continuous flash sublimation production” techniques to improve the efficiency of perovskite photovoltaics and aims to drop into existing manufacturing configurations. The startup has raised $1 million in a round led by VoLo Earth Ventures, along with Clean Energy Venture Group. 
• Microquanta Semiconductor, a Chinese firm, is building panels from glass-packaged perovskites and has recently pulled in $55 million in funding.
• Oxford PV has raised more than $140 million to develop perovskite-on-silicon tandem solar cells and modules. Meyer Burger has partnered with the startup to develop equipment and has also taken an equity stake in the firm. 
• Saule Technologies is developing an inkjet printing technique for manufacturing perovskite solar cells packaged in bendable plastic. 
• Swift Solar stacks perovskite solar cells to make tandem cells. The Department of Energy–funded startup can deposit these layers on flexible substrates and foils.
• Tandem PV aims to monolithically print thin-film perovskites on a glass panel and mechanically stack them on top of silicon cells.

A poll

Do you think CubicPV CEO Frank van Mierlo will be proven right, or is he overly optimistic?

(If you’re having trouble seeing the poll, vote here.)

Perovskite crystal image from Los Alamos National Laboratory (Flickr cc): In recent experiments, Los Alamos National Laboratory scientists have produced perovskite crystals that exhibit solar conversion efficiencies comparable to those of silicon. This image shows the kind of high-efficiency perovskite crystals regularly produced at Los Alamos.