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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 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.


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.

Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 16-98PrototypeAvailable01/26/201701/26/2017

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To: Bill Hadley<>