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Improving the Performance of Wide-Bandgap Perovskite Solar Cells via Non-stoichiometric Solution Chemistry

National Renewable Energy Laboratory

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Technology Marketing Summary

Perovskite halides (e.g. CH3NH3PbI3 or MAPbI3) are a new class of light absorbers with exceptional and unparalleled progress in solar cell performance. A perovskite is any material with a specific ABX3 crystal structure, wherein an organic based cation is A, a metal cation is B, and a divalent halide anion is X. Work on solar cells using these perovskite materials has advanced rapidly as a result of the material’s excellent light absorption, charge-carrier mobilities, and lifetimes that result in high device efficiency with low-cost, industry-scalable technology. However, this potential for low cost and scalability requires overcoming barriers hindering the commercialization of perovskite devices related to perovskite stability, efficiency, and environmental compatibility. NREL researchers have made significant technical contributions within six areas critical to developing commercialized perovskite devices, which include increases in film efficiency and stability and innovations in perovskite film deposition methods, film chemistry, hole and electron extraction layer engineering, and device architecture.


Low cost, scalable perovskite manufacturing methods show great promise for tandem solar cell applications in which a perovskite layer is deposited on top of a silicon (Si) layer. These devices would substantially increase device efficiency compared to a Si-only cell without introducing impractical additional costs. In order to integrate these technologies, however, a high quality perovskite layer with a bandgap larger than that of Si is needed.

Researchers at NREL have created wide-bandgap perovskite devices with improved performance by using a non-stoichiometric precursor chemistry with excess methylammonium halides. When an iodine-rich precursor solution was used the resulting device exhibited a bandgap of 1.71 eV, a more ideal bandgap than that of existing perovskite tandems. Researchers also used a bromide-rich precursor solution to create a device with improved crystallographic properties (crystallinity and orientation) with a sufficiently high bandgap of 1.75 eV without greatly affecting the final perovskite composition. A tandem perovskite-Si cell created with this method demonstrated an efficiency of 20.3%.

This technology is within the Film Chemistry group of NREL’s perovskite portfolio. For further information regarding NREL's broader perovskite portfolio, please visit NREL's Perovskite Patent Portfolio website.

The Perovskite Film Chemistry category consists of alternative film chemistries to the common methylammonium lead halide (CH3NH3PbI3) perovskite devices. These alternative film compositions have been shown to improve the performance of perovskite films, demonstrating both increased stability and efficiency, and to enable perovskite use in alternative mediums such as quantum dots.

  • Decreased bandgap of 1.71 eV
  • Improved crystallinity and orientation without affecting the final perovskite composition
Applications and Industries
  • Perovskite photovoltaics
  • Tandem solar cells (Si, CIGS, CdTe)
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 17-100PrototypeAvailable04/27/201804/27/2018

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To: Bill Hadley<>