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

Stage: Development
Perovskite photovoltaics are a new class of light absorbers with exceptional and unparalleled progress in solar power performance. A perovskite is any material with a specific ABX3 crystal structure. In photovoltaic applications, the A cation can be either organic, inorganic, or hybrid in composition. The B component is typically a metal cation such as lead, and X is a halide such as iodine or bromine. Work on solar cells using perovskite materials has advanced rapidly as a result of the material’s excellent light absorption, charge-carrier mobilities, and lifetimes – resulting in high device efficiencies with low-cost, industry-scalable technology. While the potential for perovskite photovoltaic devices is high, commercialization will require overcoming other challenges relating to material stability, efficiency, and environmental compatibility.

Low cost, scalable perovskite manufacturing methods show great promise for tandem solar cell applications in which a perovskite absorber layer is deposited on top of a low-bandgap (e.g. Silicon) sub-cell. These devices would substantially increase device efficiency compared to a Si-only cell without significantly increasing the overall cost. In order to integrate these technologies, however, a high-quality perovskite layer with an optimally-wide bandgap is required.

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 an ideal bandgap of 1.71 eV. When a Bromine-rich precursor solution is utilized, a 1.75 eV perovskite film with desirable crystallographic properties (crystallinity and orientation) is created. 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 Film Chemistry group 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 by demonstrating both increased stability and efficiency, and to enable perovskite use in alternative mediums such as quantum dots.

For more information, contact Bill Hadley at Bill.Hadley@nrel.gov

ROI 17-100

Applications and Industries

  • Perovskite photovoltaics
  • Tandem solar cells (Si, CIGS, CdTe)


  • Decreased bandgap of 1.71 eV
  • Improved crystallinity and orientation without affecting the final perovskite composition