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

National Renewable Energy Laboratory

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Technology Marketing Summary

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.

  • Improved conversion efficiency and VOC and ­FF
  • Enhanced conductivity
  • Reduced hysteresis
Applications and Industries
  • Perovskites
  • Photovoltaics
More Information

For further information on the status of the provisional patent application, please contact Bill Hadley.

Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Application 20180005762
An aspect of the present disclosure is a device that includes a first layer that includes a hole-transport material and an acid, where the first layer has a conductivity between 20 .mu.S/cm and 500 .mu.S/cm. In some embodiments of the present disclosure, the first layer may absorb light having a wavelength between 400 nm and 600 nm. In some embodiments of the present disclosure, the hole-transport material may include at least one of 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), a derivative of spiro-OMeTAD, poly(triarylamine), poly(3-hexylthiophene), and/or N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine.
National Renewable Energy Laboratory 06/29/2017
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 16-98PrototypeAvailable01/26/201701/26/2017

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To: Bill Hadley<>