Graphene, Perovskites, and Silicon -- An Ideal Tandem

Graphene Flagship researchers at the University of Rome Tor Vergata, the Italian Institute of Technology (IIT) and its spin-off, Graphene Flagship Associate Member BeDimensional, in cooperation with ENEA have successfully combined graphene with tandem perovskite-silicon solar cells to achieve efficiencies of up to 26.3%. Moreover, they envisioned a new manufacturing method that, thanks to the versatility of graphene, allows to reduce production costs and could lead to the production of large-area solar panels. Graphene-based tandem solar cells almost double the efficiency of pure silicon.

Laws of physics limit the maximum efficiency of silicon solar cells to 32%. For that reason, scientists have spent decades trying to come up with other alternatives, such as III-V and perovskites. However, the latter present several manufacturing challenges, and scaling up the production of solar panels is a key step towards success. With 'tandem cells', scientists had previously combined the advantages of both silicon and perovskites - however stability, efficiency and large-scale manufacturing still seemed like a far-fledged dream.

But then graphene came into play - and it could be a game changer. Graphene Flagship researchers identified its potential for energy harvesting, and in fact have dedicated two different industry-oriented 'Spearhead Projects' to dig into the possibilities of graphene-based solar cells. This new paper published in Joule - a reference journal in the field of energy research - is yet another proof that graphene and related layered materials will enable the commercialisation of more efficient and cost-effective large area solar panels.

Aldo di Carlo, lead author and researcher in Graphene Flagship partner University of Rome Tor Vergata, explains: "Our new approach to manufacture graphene-enabled tandem solar cells provides a double advantage. First, it can be applied to enhance all the different types of perovskite solar cells currently available, including those processed at high temperatures. But more importantly, we can incorporate our graphene using the widespread 'solution manufacturing methods', key to further deploy our technologies industrially and deliver large-surface, graphene-enabled solar panels."

Francesco Bonaccorso, co-author, co-founder of Graphene Flagship spin-off BeDimensional, says: "This innovative approach proposed in the context of the Graphene Flagship is the first step toward the development of tandem solar cells delivering an efficiency higher than the limit of single junction silicon devices. Layered materials will be pivotal in reaching this target.".

Emmanuel Kymakis, Graphene Flagship Energy Generation Work Package Leader, says: "There are some compatibility issues that have to be tackled before the full exploitation of the perovskite-Si tandem PVs concept. This pioneering work demonstrates that the integration of GRMs inks with on-demand morphology and tuneable optoelectronic properties in a tandem structure, can lead to high-throughput industrial manufacturing. Graphene and related materials improve the performance, stability and scalability of these devices. The stacked silicon-perovskite configuration will act as the foundation of the new Graphene Flagship Spearhead Project GRAPES, in which a pilot line fabrication of graphene-based perovskite-silicon tandem solar cells will take place, paving the way towards breaking the 30% efficiency barrier and a significant decrease on the Levelized Cost of Energy."

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship and Chair of its Management Panel, adds: "The application of graphene and related materials to solar energy generation was recognized as a strategic priority since the start of the Graphene Flagship. The first graphene-based solar farm is being set up this year. These new results underpin our effort for the following 3 years to produce panels defining the state of the art. This also shows how the work of the Graphene Flagship strongly aligns with the UN's Sustainable Development Goals."

EurekAlert!, the online, global news service operated by AAAS, the science society: https://www.eurekalert.org/pub_releases/2020-03/gf-gpa030320.php