Dr. Ptak is a Senior Scientist in the National Center for Photovoltaics. He received his doctorate from West Virginia University where he worked on growth kinetics and doping of III-Nitride materials grown by molecular beam epitaxy (MBE). He joined NREL after graduation in 2001 and has since worked on the growth and characterization of various materials and devices, including dilute nitrides and dilute bismides, coincident-site lattice matched alloys, and other novel materials for photovoltaic applications. 

He currently leads an effort to drastically reduce the cost of high-efficiency III-V solar cells, focused on the use of hydride vapor phase epitaxy to enable the use of highly efficient III-V materials in one-sun and low-concentration applications. Dr. Ptak has authored or co-authored more than 125 papers and 2 book chapters, given more than 100 invited and contributed presentations, and been awarded 6 patents. His research interests include growth kinetics, new materials, low-cost III-V deposition techniques, and photovoltaic materials and devices.

Featured Work

A.J. Ptak, M.R. Millecchia, T.H. Myers, K.S. Ziemer, and C.D. Stinespring "The Relation of Active Nitrogen Species to High-Temperature Limitations for (0001) GaN Growth by Radio Frequency Plasma-Assisted Molecular Beam Epitaxy," Appl. Phys. Lett. 74, 3836 (1999).

A.J. Ptak, D.J. Friedman, Sarah Kurtz, and R.C. Reedy, “Low-acceptor-concentration GaInNAs grown by molecular-beam epitaxy for high-current p-i-n solar cell applications,” J. Appl. Phys. 98, 94501 (2005).

A.J. Ptak, R. France, D.A. Beaton, K. Alberi, J. Simon, A. Mascarenhas, and C.-S. Jiang, “Kinetically-limited growth of GaAsBi by molecular-beam epitaxy,” J. Cryst. Growth. 338, 107 (2012).

J. Simon, K.L. Schulte, D.L. Young, Nancy M. Haegel, and A.J. Ptak, “GaAs Solar Cells Grown by Hydride Vapor Phase Epitaxy and the Development of GaInP Cladding Layers,” IEEE J. Photovoltaics 6, 191 (2016).

C.A. Sweet, K.L. Schulte, J.D. Simon, M.A. Steiner, N. Jain, D.L. Young, A.J. Ptak, and C.E. Packard, “Controlled exfoliation of (100) GaAs-based devices by spalling fracture,” Appl. Phys. Lett. 108, 011906 (2016).

K.L. Schulte, J. Simon, and A.J. Ptak, “Multijunction GaInP/GaAs Solar Cells Grown by Hydride Vapor Phase Epitaxy,” Progress in Photovoltaics 26, 887 (2018).