Biosketch

Dr. William N. Shafarman joined the Materials Science Department after working since 1986 at the Institute of Energy Conversion where he is now the Director. His research group investigates materials, processing, and characterization of compound semiconductors for their application in thin film solar cells and related optoelectronic applications. This research has had a particular emphasis on copper indium gallium diselenide [Cu(InGa)Se2] and related alloys along with newer, promising materials including hybrid perovskites. At IEC, these thin films are deposited using a wide range of processes and in the fabrication of complete solar cell devices. The main objective of this research is to explore the complex relationships between processing, materials properties, device design, and electronic characteristics of the solar cells. In this work, he has collaborated extensively with university and industrial research groups both in the US and internationally. Dr. Shafarman earned his Ph.D. in physics from the University of Rochester after earning his B.S. in physics from the University of Delaware.

Research Interests

• Alloying and bandgap engineering of thin film chalcogenide materials
• New compound materials for photovoltaics and related optoelectronic applications
• Design and validation of new device structures and contacts
• Development thin film deposition processes to facilitate manufacturing scale-up

Representative Publications

 “The Growth of Methylammonium Lead Iodide Perovskites by Close Space Vapor Transport” Alexander J. Harding, Austin G. Kuba, Brian E. McCandless, Ujjwal K. Das, Kevin D. Dobson, Babatunde A. Ogunnaike, William N. Shafarman, RSC Advances 10, 16125 (2020). https://doi.org/10.1039/D0RA01640C

“Precursor reaction method with high Ga Cu(In,Ga)(S,Se)₂ to achieve increased open-circuit voltage” Isaac K. Lam, Gregory M. Hanket, William N. Shafarman, IEEE Journal of Photovoltaics 10, 1185-1190 (2020).  https://doi.org/10.1109/JPHOTOV.2020.2984017

“Influence of Ga on the KF Treatment Chemistry for CIGS Solar Cells” Nicholas Valdes, Kevin Jones, Robert Opila, William Shafarman, IEEE Journal of Photovoltaics 9, 1846-1851, (2019).  https://doi.org/10.1109/JPHOTOV.2019.2930210

“Comparison of Ag and Ga alloying in low bandgap CuInSe₂-based solar cells” Nicholas Valdes, JinWoo Lee, William Shafarman Solar Energy Materials & Solar Cells 195, 155-159 (2019).  https://doi.org/10.1016/j.solmat.2019.02.022

“Ag Alloying and KF Treatment Effects on Low Bandgap CuInSe₂ Solar Cells” Nicholas Valdes, JinWoo Lee, William Shafarman IEEE Journal of Photovoltaics 9, 906-911, (2019).  https://doi.org/10.1109/JPHOTOV.2019.2899962

“Reaction Rate Enhancement for Cu(In,Ga)Se₂ Absorber Materials using Ag-alloying” Sina Soltanmohammad, Ho Ming Tong, Timothy J. Anderson, William N. Shafarman, IEEE Journal of Photovoltaics 9, 898-905 (2019).     
https://doi.org/10.1109/JPHOTOV.2019.2897582

“Voltage-Induced Charge Redistribution in Cu(In,Ga)Se₂ Devices Studied With High-Speed Capacitance-Voltage Profiling” Jeff Bailey, Dmitry Poplavskyy, Geordie Zapalac, Lorelle Mansfield, William Shafarman, IEEE Journal of Photovoltaics. 9, 319-324 (2019).                          
https://doi.org/10.1109/JPHOTOV.2018.2882204

“Reaction Pathway Analysis of (Ag_xCu_1-x)(In_0.75Ga_0.25)Se₂ with x = 0.75 and 1.0” Sina Soltanmohammad and William N. Shafarman, Solar Energy Materials & Solar Cells 182, 142-57 (2018).  https://doi.org/10.1016/j.solmat.2017.12.023.

“High V_OC in (Cu,Ag)(In,Ga)Se₂ solar cells” Marika Edoff , Tobias Jarmar, Nina Shariati Nilsson, Erik Wallin, Daniel Högström, Olof Stolt, Olle Lundberg, William Shafarman and Lars Stolt, IEEE Journal of Photovoltaics 7, 1789 – 1794 (2017). https://doi.org/10.1109/JPHOTOV.2017.2756058

“Phase Stability in Ag-Cu-In-Ga Metal Precursors for (Ag,Cu)(In,Ga)Se₂ Thin Films” Sina Soltanmohammad, Lei Chen, Brian McCandless, William N. Shafarman, Solar Energy Materials & Solar Cells 172, 347–352 (2017).                    
https://doi.org/10.1016/j.solmat.2017.08.009

“An improved method for determining carrier densities via drive level capacitance profiling” Charles W. Warren, Ellis T. Roe, D. Westley Miller, William N. Shafarman, Mark C. Lonergan, Applied Physics Letters 110, 203901 (2017).             
https://doi.org/10.1063/1.4983367

“A quaternary Laves-type phase in Ag-Cu-In-Ga thin films” Sina Soltanmohammad, Brian McCandless, William N. Shafarman, Journal of Alloys and Compounds 710 819-824 (2017).  https://doi.org/10.1016/j.jallcom.2017.03.228

“Secondary Phase Formation in (Ag,Cu)(In,Ga)Se₂ Thin Films Grown by Three-stage Co‑evaporation” Lei Chen, Sina Soltanmohammad, JinWoo Lee, Brian E. McCandless, William N. Shafarman, Solar Energy Materials & Solar Cells 166, 18-26, (2017).                       
https://doi.org/10.1016/j.solmat.2017.03.001

“Grain engineering: How nanoscale inhomogeneities can control charge collection in solar cells” Bradley M. West, Michael Stuckelberger, Harvey Guthrey, Lei Chen, Barry Lai, Jörg Maser, Volker Rose, William Shafarman, Mowafak Al-Jassim, Mariana I. Bertoni, Nano Energy 32 488–493 (2017).  https://doi.org/10.1016/j.nanoen.2016.12.011

“Comparison of CIGS Solar Cells Made With Different Structures and Fabrication Techniques” Lorelle M. Mansfield, Rebekah L. Garris, Kahl D. Counts, James R. Sites, Christopher P. Thompson, William N. Shafarman, Kannan Ramanathan, IEEE Journal of Photovoltaics 7, 286-293 (2017).  https://doi.org/10.1109/JPHOTOV.2016.2616188

“Alternative device structures for CIGS-based solar cells with semi-transparent absorbers,” Kihwan Kim, William N. Shafarman, Nano Energy 30, 488-493 (2016).  https://doi.org/10.1016/j.nanoen.2016.10.038

“Ag–Cu–In–Ga Metal Precursor Thin Films for (Ag,Cu)(In,Ga)Se2 Solar Cells” Sina Soltanmohammad, Lei Chen, Brian McCandless, William N. Shafarman, IEEE Journal of Photovoltaics 7, 273-280 (2017).  https://doi.org/10.1109/JPHOTOV.2016.2615682

“Design and experimental implementation of an effective control system for thin film Cu(InGa)Se₂ production via rapid thermal processing”, Robert J. Lovelett, Gregory M. Hanket, William N. Shafarman, Robert W. Birkmire, Babatunde A. Ogunnaike, Journal of Process Control 46 24–33 (2016).  https://doi.org/10.1016/j.jprocont.2016.07.005

“Development of Cu(In,Ga)Se₂ superstrate devices with alternative buffer layers” Peipei Xin, Jes K. Larsen, Fei Deng, William N. Shafarman, Solar Energy Materials & Solar Cells 157, 85–92 (2016).  https://doi.org/10.1016/j.solmat.2016.05.018

“A stochastic model of solid state thin film deposition: application to chalcopyrite growth” Robert J. Lovelett, Xueqi Pang, Tyler M. Roberts, William N. Shafarman, Robert W. Birkmire, Babatunde A. Ogunnaike, AIP Advances 6, 045015 (2016).                
https://doi.org/10.1063/1.4948404

“Structural and optical properties of (Ag,Cu)(In,Ga)Se₂ polycrystalline thin film alloys” J. H. Boyle, B. E. McCandless, W. N. Shafarman, and R. W. Birkmire, Journal of Applied Physics 115 , 223504 (2014).  https://doi.org/10.1063/1.4880243

“Backwall superstrate configuration for ultrathin Cu(In,Ga)Se₂ solar cells” J. K. Larsen, H. Simchi, P. Xin, K. Kim,  and W. N. Shafarman Applied Physics Letters 104, 033901 (2014).  https://doi.org/10.1063/1.4862651

“Structure and interface chemistry of MoO₃ back contacts in Cu(In,Ga)Se₂ thin film solar cells” Hamed Simchi, Brian E. McCandless, T. Meng, and William N. Shafarman, Journal of Applied Physics 115, 033514 (2014).  https://doi.org/10.1063/1.4862404

“Effect of Reduced Cu(InGa)(SeS)₂ Thickness Using Three-Step H₂Se/Ar/H₂S Reaction of Cu–In–Ga Metal Precursor” Kihwan Kim, Hyeonwook Park, Woo Kyoung Kim, Gregory M. Hanket and William N. Shafarman, IEEE Journal of Photovoltaics, 3, 446-50 (2013).
https://doi.org/10.1109/JPHOTOV.2012.2219501

“Three-step H₂Se/Ar/H₂S reaction of Cu-In-Ga precursors for controlled composition and adhesion of Cu(In,Ga)(Se,S)₂ thin films” Kihwan Kim, Gregory M. Hanket, Trang Huynh, William N. Shafarman. Journal of Applied Physics, 111, 083710 (2012).                
https://doi.org/10.1063/1.4704390

“Cu(InGa)Se₂ Solar Cells,” W.N. Shafarman, S. Siebentritt, and L. Stolt, Chapter 13 in Handbook of Photovoltaic Science and Engineering, Second Edition, ed. by A. Luque and S. Hegedus, John Wiley & Sons, Ltd., 546 (2011).   https://doi.org/1002/9780470974704.ch13

“Cu(InGa)Se₂ Solar Cells on a Flexible Polymer Web,” R.W. Birkmire, E. Eser, S. Fields and W.N. Shafarman, Progress in Photovoltaics 13, 141 (2005).   https://doi.org/10.1002/pip.605

“Thin Film Solar Cells: Device Measurements and Analysis,” S.S. Hegedus and W.N. Shafarman, Progress in Photovoltaics 12, 155 (2004).  https://doi.org/10.1002/pip.518

“Bulk and Metastable defects in CuIn_1-xGa_xSe₂ Thin Films Using Drive-Level Capacitance Profiling,” J.T. Heath, J.D. Cohen and W.N. Shafarman, Journal of Applied Physics 95, 1000 (2004).   https://doi.org/10.1063/1.1633982