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Inverted Metamorphic III-V Tandem Device for Photoelectrochemical Water Splitting

Stage: Development

The process of photoelectrochemical (PEC) water splitting is a promising pathway for the generation of hydrogen due to its high conversion efficiency and potential for cost efficiency. Additionally, it is a renewable energy technology with relatively simple and inexpensive processes compared to other hydrogen production technologies. However, continued improvements in conversion efficiency, durability, and processing cost are needed to make the technology viable for use in the future hydrogen economy.

Scientists at the National Renewable Energy Laboratory (NREL) have invented a novel tandem GaInP/GaInAs PEC device with an architecture based on inverted metamorphic multi-junction concepts developed at NREL. This PEC device features a lattice-matched top absorber, a lattice-mismatched bottom absorber, a transparent tunnel junction, and a transparent graded buffer layer interposed between the two junctions for electrical interconnection and strain mitigation. The champion GaInP/GaInAs device with a 1.8/1.2-eV bandgap combination was benchmarked while an AlGaAs/GaInAs 1.7 eV/1.2 eV proof-of-concept device was also demonstrated. The architecture platform allows the bandgaps of both the top and bottom absorbers to be easily varied by tuning the III-V alloy compositions toward the predicted optimal 1.7/1.1 eV bandgap combination.

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

U.S. Patent # 10,087,535 B2

ROI 14-37

Applications and Industries

  • Photoelectrochemical water splitting
  • Hydrogen fuel production


  • Renewable fuel production from sunlight
  • High solar-to-fuel conversion efficiency
  • Flexible platform for further optimizing performance
  • Technology demonstrated in photovoltaic applications
  • Inverted design amenable to substrate removal and reuse
  • Reduces the balance-of system cost for water splitting