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Passivating Window and Capping Layers for Improved Photoelectrochemical (PEC) Efficiency and Durability

Stage: Development

Hydrogen is a clean burning fuel that has been proposed as a substitute for gasoline in the transportation sector, as well as an important feedstock for ammonia fertilizers essential to the global fuel supply. Unfortunately, the current process which dominates hydrogen generation converts fossil fuels into hydrogen and releases significant amounts of carbon dioxide (CO2) and other greenhouse gases. In order for hydrogen to become a truly clean technology new methods of generation must be found. One promising early stage solution is the splitting of water into hydrogen and oxygen using solar energy from semiconductor cells.

Researchers at NREL have created a novel photoelectrochemical (PEC) cell which converts solar energy to stored energy in hydrogen bonds at an unprecedented efficiency of 16%. The device uses another NREL invention, the inverted metamorphic multijunction (IMM) cell, optimized for water-splitting to achieve the record efficiency. The use of an IMM cell with a transparent graded buffer allowed the researchers to vary the cell junction bandgaps independently to generate a higher photocurrent, which correlates directly with water-splitting conversion efficiency. This new high efficiency cell can reduce balance of system costs to make hydrogen production via PEC pathways more economic.

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

ROI 16-114

Applications and Industries

  • Hydrogen production
  • Hydrogen powered transportation
  • Hydrogen fuel cells
  • Fertilizer and agriculture


  • Emission-free hydrogen production
  • Storable solar energy