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In the last ten years a huge amount of research has focused on the use of Perovskite materials as semiconductors that can be tuned to harvest energy from the sun. Light from the sun excites electrons in the perovskite material, and through clever engineering these electrons can be harnessed to produce electric current. First introduced in the 1950s, modern solar panels use silicon as the semiconductor. Silicon requires a lot of energy to produce and is expensive to manufacture, factors which have driven many researchers to replace silicon with perovskite-based systems – however that technology is still someway off, and we need better solar energy systems right now.

Tandems for Efficient and Advanced Modules using Ultrastable Perovskites, or TEAMUP, a project that has just secured $9M in federal funding from the U.S. Department of Energy Solar Technologies Office (SETO), brings together a consortium of researchers from Academic (CU Boulder, Northwestern University, Arizona State University and UC Merced), Industrial (Swift Solar, Tandem PV and Beyond Silicon) and Federal Labs (the National Renewable Energy Laboratory), who have a near term solution for more efficient solar panels using a combination of the new perovskite-based systems and the existing silicon-based systems. So-called Tandem perovskite-silicon solar modules bring together the best of both technologies by putting a layer of perovskite on top of silicon-based devices, boosting the efficiency of capturing solar power. Because this approach builds on top of existing silicon-based technologies instead of completely replacing it, it can be more quickly realized and deployed, even potentially upgrading existing installations. Accessing these more efficient and affordable solar energy harvesting technologies is crucial for transitioning more communities to renewable energy sources in a fair and just fashion.

The tandem perovskite-silicon research community is currently working to answer three main questions on the path to commercialization; how to combine the perovskite and silicon devices (monolithic or mechanically stacked tandems), how to create and process the perovskite layer (vapor or solution processing) and how to make the tandem devices more stable and robust. The TEAMUP consortium has chosen not to limit their research focus by selecting one particular device strategy or processing approach and instead adopting a collaborative approach that brings together expertise across these disciplines to address the stability of tandem solar modules. By working together in this unique innovation ecosystem, one in which researchers who might otherwise be considered competitors can openly share the advantages and disadvantages of each approach, understanding of the challenges can be enhanced and realization of solutions that are applicable broadly, across the different strategies, can be accelerated.

Mike McGehee, the lead investigator from CU Boulder says “We have an extraordinary team who bring many different types of expertise to the Consortium and I look forward to seeing what we can accomplish”. Colin Bailie, Founder and CEO of Tandem PV comments on the collaborative nature of this project “Tandem PV and Swift Solar have long sought to work directly together and with the broader US research community on common research topics that can be solved more quickly as a group. We are excited by the opportunity to work on the same team and not as competitors”.

“We have an extraordinary team who bring many different types of expertise to the Consortium and I look forward to seeing what we can accomplish” - Mike McGehee, TEAMUP lead PI

The key to long-term, real-world operation of these solar modules is the stability of these systems. Solar panels are expected to survive extreme conditions – the heat of the day and the cold of night can provide significant swings in temperature, humidity and general weather scenarios. Under these conditions the perovskite materials can degrade – in the same way that a metal can rust. This can cause reduction in performance efficiencies and lead to blistering in the solar modules. Researchers in TEAMUP are developing strategies to contain and protect the perovskite layers from degradation and enhance stability and real-world operation.

The teams have outlined a two-stage iteration process; innovation followed by comprehensive testing. The innovation stage will explore different perovskite materials, device structures and fabrication approaches. The testing stage will use a comprehensive suite of tools to simulate long-term use under real-world conditions and characterize how these new solar modules perform, the experience and understanding from which will be fed back into the innovation stage. By collecting data at every step of this feedback process TEAMUP will build detailed forecasting models capable of describing performance in real world conditions over a 25 year period, a critical tool in taking this technology to a commercial product.

The importance of the tandem module technology was highlighted by Colin Bailie “Perovskite-silicon tandems represent not only the opportunity to make solar more affordable for more communities in the US, but also a unique opportunity to return the United States to a position of leadership in solar manufacturing and develop a domestic manufacturing base around this new technology. TEAMUP’s success will ensure perovskite-silicon tandems are in a strong technological position as companies prepare for mass production”. Tomas Leijtens, Co-Founder and CTO of Swift Solar agrees “We’re excited to work with this diverse team to tackle the most pressing stability and performance challenges as we scale up perovskite solar technology. This consortium should help accelerate perovskite tandem commercialization in the US”.

Understanding and solving the degradation mechanisms that negatively impact stability in tandem perovskites is essential to demonstrating their feasibility to future investors and customers. By adopting an approach that is agnostic to both perovskite processing and device design, TEAMUP will develop solutions that can be applied across a wide cross-section of the perovskite industry.