Howard Branz — Research Fellow
Dr. Branz is a leader in film, crystal, and amorphous silicon photovoltaic research and development in the National Center for Photovoltaics. He is recognized for his creative approaches to putting quality crystal Si films on inexpensive substrates, for the development of new methods of cheaply fabrication nano-structured anti-reflective "black" silicon, and for his studies of transport, defects and hydrogen diffusion in amorphous semiconductors. In 1998, Branz proposed and published the widely-cited hydrogen collision model of metastable degradation. He has also worked in fields as diverse as photoelectrochemical hydrogen production, electrochromics, memory switching devices, neutron detectors and field-induced DNA motion. Branz has published more than 110 papers in refereed scientific journals and has about 20 U.S. patents issued or pending.
In 2011, a team led by Branz developed a confirmed 18.2% efficient black silicon solar cell—the best intentionally-nanostructured solar cell ever made. This technology is now being commercialized by Natcore Technology. Dr. Branz also led a cooperative research initiative that launched a venture-capital-funded start-up, Ampulse Corp., using an NREL-developed chemical vapor deposition process to grow the silicon on Oak Ridge National Laboratory's inexpensive textured rolled-metal foil.
Dr. Branz began his scientific career as an Associate Engineer at in the MIT Lincoln Laboratory Photovoltaic Systems Engineering group. After completing his Ph.D. thesis at MIT under the direction of Profs. David Adler and John Haggerty on hydrogenated amorphous silicon (a-Si:H) growth, transport physics, and solar cells, Dr. Branz joined NREL in 1987. From 1996 to 2001, Branz led the NREL Amorphous Silicon Photovoltaics Team. From 2003 to 2007, Branz was Manager of the NCPV Silicon Materials and Devices Group. From April 2012, Branz will be on assignment as a Program Director at the DOE Advanced Research Projects Agency (ARPA-E), while continuing to participate in NREL research.
- Film crystal silicon photovoltaics
- Defects, metastability, and diffusion in semiconductors
- Amorphous semiconductors
- Solar hydrogen production
- Nanostructured black silicon antireflection
- Massachusetts Institute of Technology (MIT), Cambridge, MA, Ph.D. in Physics (1987)
- Brandeis University, Waltham, MA, B.A. in Physics (1978).
- Founding Fellow, Renewable and Sustainable Energy Institute (RASEI), a joint institute of NREL and the University of Colorado, 2011–2012
- Session Organizer, 16th American Conference on Crystal Growth and Epitaxy, 2005, (ACCGE-16)
- Co-Chair, 22nd International Conference on Amorphous and Nanocrystalline Semiconductors, 2007 (ICANS22)
- Co-organizer MRS Spring Meeting Amorphous and Microcrystalline Silicon Symposium, 1998, 1999 and 2000
Program Committee Member
- International Conference on Amorphous Nanocrystalline Semiconductors
- 25th Conference, Toronto 2012
- 24th Conference, Nara, Japan, 2011
- 23rd Conference, Netherlands, 2009
- 21st Conference, Portugal, 2005
- SPIE Solar Energy and Technology Conference, San Diego, 2011, 2012
- 1st International Workshop on the Staebler-Wronski Effect, Berlin 2009
- International Symposium on Solar Cell Technologies, Taiwan, 2008
- MRS Symposium A on Amorphous and Microcrystalline Silicon, San Francisco, 1997.
Government Science and Technology Report Author or Contributor
- DOE Energy Efficiency and Renewable Energy Film Silicon Photovoltaic Roadmap, 2011
- NIST Grand Challenges for Advances in Photovoltaic Technologies and Measurements, 2010
- DOE Energy Efficiency and Renewable Energy Film Silicon Photovoltaic Roadmap, 2007
- DOE Basic Energy Sciences Basic Research Needs for Solar Energy Utilization, April 2005.
- 2012: NREL's Hubbard Award for "sustained high-level research contributions and leadership in renewable energy"
- 2011: Federal Laboratory Consortium National Award for Excellence in Technology Transfer for Ampulse "Flexible Thin Film Solar Photovoltaics on RABiTS"
- 2010: R&D 100 Award for "Black Silicon Nanocatalytic Etch"
- 2010: Southeast Regional Laboratory Consortium Award for Excellence in Technology Transfer for Ampulse "Flexible Thin Film Solar Photovoltaics on RABiTS"
- 1999: NREL Staff Award for Outstanding Research for "Hydrogen Collision Model of Amorphous Silicon Metastability"
- 1997: Fulbright Scholar
- Conference Plenary Talks
- 2011: SPIE Solar Energy and Technology Conference, San Diego, CA
- 2001: 19th International Conference on Amorphous and Microcrystalline Semiconductors, Nice, France
- Twenty Seven Conference Invited Talks, including
- 2012: SPIE Photonic Europe Photonics for Solar Energy Systems, Brussels, Belgium
- 2011: 5th Conference on Silicon Solar Cells, Boston, MA
- 2010: Electrochemical Society Annual Meeting, Las Vegas, NV
- 2010: Photovoltaics for Emerging Energy Technologies, Albuquerque, NM
- 2010: DARPA Black Si Workshop, Washington, DC
- 2009: 6th Intl. Conference on Si Epitaxy, Los Angeles, CA
- 2009: MRS Spring Meeting Symposium A, San Francisco, CA
- 2009: 4th International Hot-Wire CVD Conference, Paris
- 2009: 1st International Workshop on Staebler-Wronski Effect, Berlin
- 2009: Center for Revolutionary Solar Photoconversion, Annual Meeting, Golden, CO
- 2009: Stanford Workshop on Inorganic Photovoltaics, Palo Alto, CA
- 2009: 23rd International Conference on Amorphous and Nanocrystalline Semiconductors, Utrecht, Netherlands
- 2009: MIT-OSA Optics and Photonics for Advanced Energy Technology, Cambridge, MA.
- Teplin, C.W.; Paranthaman, M.P.; Fanning, T.R.; Alberi, K.; Heatherly, L.; Wee, S.-H.; Kim, K.; List, F.A.; Pineau, J.; Bornstein, J.; Bowers, K.; Lee, D.F.; Cantoni, C.; Hane, S.; Schroeter, P.; Young, D.L.; Iwaniczko, E.; Jones, K.M.; and Branz, H.M., "Heteroepitaxial film crystal silicon on Al2O3 for solar cells on cube-textured metal foil," Energy and Environmental Science, DOI: 10.1039/C1EE01555A, 2011.
- Oh, J.; Deutsch, T.G.; Yuan, H.-C.; and Branz, H.M., "Nanoporous black silicon photocathode for H2 production by photoelectrochemical water splitting," Energy and Environmental Science, vol. 4, 2011, pp. 1690–94.
- Alberi, K.; Martin, I.T.; Shub, M.; Teplin, C.W.; Romero, M.J.; Iwaniczko, E.; Duda, A.; Stradins, P.; Branz. H.M.; Young, D.L. "Material quality requirements for efficient epitaxial film silicon solar cells," Appl. Phys. Lett., Vol. 96, 2010; pp. 73502.
- Yuan, H.-C.; Yost, V.E.; Page, M.R.; Stradins, P.; Meier, D.L.; Branz, H.M. "Efficient black silicon solar cell with a density-graded nanoporous surface: Optical properties, performance limitations and design rules," Appl. Phys. Lett., Vol. 95, 2009; pp. 123501.
- Teplin, C.W.; Jiang, C.S.; Stradins, P.; Branz, H.M. "Cone kinetics model for two-phase film silicon deposition." Appl. Phys. Lett., Vol. 92, 2008; pp. 93114–6.
- Du, M.-H.; Branz, H.M.; Crandall, R.S.; Zhang, S.B. "Self-trapping enhanced carrier recombination at light-induced boron-oxygen complexes in silicon," Phys. Rev. Lett., Vol. 97, 2006; pp. 256602–5.
- Branz, H.M. "The hydrogen collision model: Quantitative description of metastability in amorphous silicon," Phys. Rev. B, Vol. 59, 1999; pp. 5498–5512.
- Yelon, A.; Movaghar, B.; Branz, H.M. "Origin and consequences of the compensation (Meyer-Neldel) law," Phys. Rev. B, Vol. 46, 1992; pp. 12244–12250.