The Solar Energy Technologies Office supports research and development projects that increase the efficiency and lifetime of hybrid organic-inorganic perovskite solar cells, as well as evaluate new materials for them.
Perovskite solar cells have shown remarkable progress in recent years with rapid increases in conversion efficiency, from reports of about 3% in 2006 to 23.3% in 2018. While perovskite solar cells have become highly efficient in a very short time, a number of challenges remain before they can become a competitive commercial technology.
Much of the recent work on perovskite solar cells has been dominated by absorber materials based on methylammonium lead halide. Although perovskite materials have been studied for more than a century, initial studies on methylammonium lead halides for semiconductor applications started in the past two decades. Initial applications of perovskite absorbers in solar cells occurred in 2006 and were published in 2009. However, these cells were not very efficient (less than 4%) and were not stable, since they relied on a corrosive liquid phase that slowly disrupted other layers within the device. By 2012 the liquid-phase components had been replaced with solid-state contacts and the efficiency was improved to 10%. Subsequent improvements in performance and stability have come through continued investigation of new materials, new device architectures, and improved fabrication processes, leading to a reported 20% cell efficiency in 2014.
Perovskite solar cells have demonstrated competitive efficiencies with potential for higher performance, but the stability of perovskite solar cells is limited compared to that of leading PV technologies: They don’t stand up well to moisture, extended periods of light, or high heat. To increase stability, researchers are studying the degradation in both the perovskite materials and the contact layers. Improved cell durability is paramount for development of commercial perovskite solar products.
Additional barriers to commercialization are the potential environmental impacts related to the perovskite absorber, which is lead-based. As such, current and future materials are being studied to evaluate, reduce, mitigate, and potentially eliminate toxicity and environmental concerns. Current materials discovery efforts are evaluating lead-free perovskite structures in order to reduce or eliminate these potential issues.
Another useful application for perovskite solar cells could be in high-performance tandem device architectures, structures in which they’re combined with another absorber material to deliver more power. Perovskite solar cells convert ultraviolet and visible light into electricity very efficiently, meaning they might be excellent tandem partners with absorber materials such as crystalline silicon that efficiently convert lower-energy light. Plus, the perovskite materials being investigated have tunable bandgaps, which means they can be custom-designed to complement the absorption of their partner material. Doing so could lead to even higher-efficiency and more cost-effective tandem PV applications.
A final and critical challenge lies in the scale-up and optimization of the fabrication processes for perovskite solar cells. If the processes were scalable and reproducible, manufacturing could increase, and perovskite PV modules could meet and potentially exceed the office’s levelized cost of electricity (LCOE) targets.
Learn more about the DOE SETO PV R&D awardees and the projects involving perovskites:
- University at Buffalo, The State University of New York (Photovoltaics Research and Development: Small Innovative Projects in Solar)
- University of Colorado Boulder (Photovoltaics Research and Development: Small Innovative Projects in Solar)
- Duke University (Next Gen III)
- National Renewable Energy Laboratory (Next Gen III)
- Stanford University (Next Gen III)
- University of Nebraska-Lincoln (Next Gen III)
- University of Washington (Next Gen III)
The scale-up of perovskite cells is an important area of research and is required to enable production of perovskite solar cells. The cells are thin-film devices that are built with layers of materials, either printed or coated from liquid inks or vacuum-deposited. Producing uniform, high-performance perovskite material in a large-scale manufacturing environment is difficult and has resulted in a substantial difference in performanc between small-area cell efficiency and large-area module performance. The future of perovskite manufacturing will likely depend on solving this challenge, which remains an active area of work within the PV research community.