U.S. Department of Energy

Next-Generation Thermionic Solar Energy Conversion

Stanford/SLAC logo Image of a fire-red glow above an image of small holes in the center of a flat place with grooves

Microscale-enhanced thermionic emitters will enable high efficiency solar to electrical conversion by taking advantage of both heat and light.

Stanford University and the SLAC National Accelerator Laboratory, under the 2012 SunShot Concentrating Solar Power (CSP) R&D funding opportunity announcement (FOA), is designing and testing an innovative high-temperature power cycle for CSP systems that does not require any mechanical equipment, resulting in reduced maintenance costs. In addition, the system can be integrated with conventional CSP cycles to create ultra-efficient plants.


The SLAC/Stanford University research team is creating a new solid-state energy conversion technology based on microfabricated and photon-enhanced thermionic energy converters (PTECs). When used as a topping cycle in concentrated solar thermal electricity generation, PTECs will enable system efficiencies in excess of 50%. The goals of this project are to:

  • Design thermally isolated thermionic arrays and microelectromechanical systems (MEMS)-based wafer-stack technologies for PTEC fabrication that could exceed the SunShot Initiative targets for system conversion efficiency and cost
  • Fabricate heterostructure semiconductor cathodes based on active-layer absorbers with the addition of band-engineered passivating layers to demonstrate PTECs with high quantum efficiency
  • Demonstrate a next-generation thermionic energy converter device with a stand-alone laboratory efficiency >15% as a significant intermediate step toward a stand-alone unit of >30%.


Through the use of modern design tools and wafer-scale microfabrication methods, this project is demonstrating for the first time a manufacturable approach to thermionic energy converter production that overcomes the space-charge-induced efficiency limitations of traditional thermionic devices. Also, through the novel application of appropriately designed and fabricated semiconductor heterostructure cathodes, the efficiency is being further improved by the photon-enhanced thermionic emission process.

Publications, Patents, and Awards

SunShot logo

Progress Reports
April 2013

Project Fact Sheet

The SunShot CSP R&D program seeks to accelerate progress toward the cost target of $0.06 per kilowatt-hour through novel and revolutionary research into CSP technologies. Learn about other DOE competitive awards for concentrating solar power research that are in progress.