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Methods for Making Perovskite Solar Cells Having Improved Hole-Transport Layers

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 method to enhance the conductivity of spiro-OMeTAD layers in perovskite solar cells through the use of acidic additives with Li-TFSI and/or Co (III) salts for hole transport layers. This novel method of doping the spiro-OMeTAD layer with acidic additives catalyzes the oxidation of spiro-OMeTAD by alkali metal salts and has demonstrated hydrogen bonding interactions between the acid and spiro-OMeTAD through Proton Nuclear Magnetic Resonance (1H NMR) and ultraviolet photoelectron spectroscopy (UPS) results. In addition, this method enables the development of high-efficiency, hysteresis-less TiO2-based planar perovskite solar cells with a 2% increased conversion efficiency over perovskites without an acid additive.

This technology is within the Hole and Electron Extraction Layer Engineering group 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 group 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 device interface layers such as spiro-OMeTAD.

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

ROI 16-98

U.S. Patent # 10,332,688 B2

Applications and Industries

  • Perovskites
  • Photovoltaics


  • Improved conversion efficiency and VOC and ­FF
  • Enhanced conductivity
  • Reduced hysteresis