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Single-Walled Carbon Nanotube Buffer Layer for the Enhanced Performance of Perovskite Solar Cells

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.

NREL researchers have developed a novel process of inserting an ultrathin (e.g., 5-nm) layer of purely semiconducting single-wall carbon nanotubes (s-SWCNTs) between the perovskite and spiro-OMeTAD-based hole-transport layer. This process, which comprises depositing the s-SWCNT buffer layer through simple solution processing, is compatible with future low-cost manufacturing methods and has demonstrated through transient absorption dynamics to improve hole extraction efficiency. Furthermore, this process increases both short-circuit current (JSC) and fill factor and improves the conversion efficiency of MAPbI3 perovskites by about 2% when compared to a perovskite without an s-SWCNT buffer layer.

This technology is within the Hole and Extraction Layer Engineering category of NREL's perovskite portfolio. For further information regarding NREL's broader perovskite portfolio, please visit NREL's Perovskite Patent Portfolio website.

The Hole and Electron Extraction Layer Engineering category comprises improvements to material layers in a perovskite solar cell device beyond the perovskite absorber layer itself. These technologies overcome the limitations of metal-organic device interfaces and spiro-OMeTAD interface layers.

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

ROI 16-14

U.S. Patent # 10,586,657 B2

Applications and Industries

  • Perovskites
  • Photovoltaics


  • 2% increase in conversion efficiency
  • Improves hole extraction efficiency
  • Increases JSC and fill factor