Matthew Doty

William Shafarman

Associate Professor

Interim Director, Institute of Energy Conversion

Department of Materials Science and Engineering

Email: wns@udel.edu
Phone : (302) 831-6215
164 Institute of Energy Conversion
451 Wyoming Road

Research Interests

Dr. Shafarman’s research group at the Institute of Energy Conversion (IEC) investigates materials and processing of compound semiconductors for their application in thin film solar cells and the characterization of photovoltaic devices using these materials. This research has had a particular emphasis on copper indium gallium diselenide [Cu(InGa)Se2] and related alloys along with newer, promising materials. At IEC, we deposit these films using different processes including elemental co-evaporation, hydride gas reaction of sputtered metal precursors, and roll-to-roll evaporation for flexible solar cells. A range of other materials and processes are used in the fabrication of complete solar cell devices. The main objective of our research is to explore the complex relationships between processing, materials properties, device design, and electronic characteristics of the solar cells.

Representative Publications

“CIGS Module Design and Manufacturing” William Shafarman, Chapter 4.4 in Photovoltaic Solar Energy: From Fundamentals to Applications, ed. By A. Reinders, P. Verlinden, W. van Sark, A. Freundlich, John Wiley & Sons, Ltd., 204 (2017).

“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).

“Defect Studies Using Photocapacitance Spectroscopy in the Copper Indium Diselenide Alloys,” J.D. Cohen, J.T. Heath and W.N. Shafarman, in Wide Gap Chalcopyrites, ed. by U. Rau and S. Siebentritt, Springer Scientific, 69 (2005).

“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); 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); 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); doi.org/10.1016/j.nanoen.2016.12.011

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

“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); doi.org/10.1016/j.jprocont.2016.07.005

“Effect of Reaction Temperature and Time during Two-Step Selenization and Sulfurization of Se-Coated CuGa/In Precursors”, Jaseok Koo, Sunmo Kwon, Yong-Suk Roh, Seok-Jin Lee, Ki-Young Jung, William N. Shafarman, Ji-Hyeon Park, Do Hoon Kim, Jae-Min Myoung, Woo Kyoung Kim, Electronic Materials Letters 12, 484-493 (2016); doi.org/10.1007/s13391-016-4011-2

“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); 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); doi.org/10.1063/1.4948404

“Na incorporation in Cu(In,Ga)(Se,S)2 films grown on insulator-coated stainless steel foil using a metal precursor reaction” Kihwan Kim, Erten Eser and William N. Shafarman, IEEE Journal of Photovoltaics 5 ,1222–1228 (2015); doi.org/10.1109/JPHOTOV.2015.2435366

“Composition and bandgap control in Cu(In,Ga)Se2-based absorbers formed by reaction of metal precursors” Kihwan Kim, Hyeonwook Park, Gregory Hanket, Woo Kyoung Kim and William Shafarman, Progress in Photovoltaics, 23, 765–772 (2015); doi.org/10.1002/pip.2494.

“Transparent Back Contacts for Superstrate (Ag,Cu)(In,Ga)Se2 Thin Film Solar Cells” Hamed Simchi, Jes Larsen, and William Shafarman, IEEE Journal of Photovoltaics, 5, 406-409 (2015); doi.org/10.1109/JPHOTOV.2014.2365469

“Structural, optical, and surface properties of WO3 thin films for solar cells” H. Simchi, B.E. McCandless, T. Meng, W.N. Shafarman, Journal of Alloys and Compounds 617, 609–615 (2014); doi.org/10.1016/j.jallcom.2014.08.047

“Improved Performance of Ultrathin Cu(InGa)Se2 Solar Cells With a Backwall Superstrate Configuration” Hamed Simchi, Jes Larsen, Kihwan Kim, and William Shafarman, IEEE Journal of Photovoltaics, 4, 1630-35, (2014); doi.org/10.1109/JPHOTOV.2014.2345436

“Light Trapping in Thin Film Cu(InGa)Se2 Solar Cells” James G. Mutitu, Uwadiae Obahiagbon, Shouyuan Shi, William Shafarman and Dennis W. Prather, IEEE Journal of Photovoltaics, 4, 948-53, (2014); doi.org/10.1109/JPHOTOV.2014.2307487

“The Comparison of (Ag,Cu)(In,Ga)Se2 and Cu(In,Ga)Se2 Thin Films Deposited by Three-stage Co-evaporation” Lei Chen, JinWoo Lee, and William N. Shafarman, IEEE Journal of Photovoltaics, 4, 447-51, (2014); doi.org/10.1109/JPHOTOV.2013.2280471

“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); doi.org/10.1063/1.4862404

“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); doi.org/10.1063/1.4862651

“Microstructure and phase evolution in single phase in CuInSe2 particles using elemental precursors” Emre Yassitepe, William N. Shafarman, and S. Ismat Shah, Journal of Solid State Chemistry, 23, 198-203 (2014); doi.org/10.1016/j.jssc.2014.02.023

“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). doi.org/10.1063/1.4880243

“First quadrant phototransistor behavior in CuInSe2 photovoltaics” A. Rockett, J. vanDuren, A. Pudov, and W. Shafarman, Solar Energy Materials & Solar Cells 118, 141 (2013); doi.org/10.1016/j.solmat.2013.07.032

“Effect of Rapid Thermal Processing on the structural and device properties of (Ag,Cu)(In,Ga)Se2 thin film solar cells” H. Simchi, B.E. McCandless, K. Kim, J.H. Boyle, W.N. Shafarman, Thin Solid Films 535, 102-106 (2013); doi.org/10.1016/j.tsf.2012.11.061

“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); doi.org/10.1109/JPHOTOV.2012.2219501

“Characterization of (AgCu)(InGa)Se2 Absorber Layer Fabricated by Selenization Process from Metal Precursor” Yuki Tauchi, Kihwan Kim, Hyeonwook Park and William Shafarman, IEEE Journal of Photovoltaics, 3, 467-71 (2013); doi.org/10.1109/JPHOTOV.2012.2221083

“Characterization of reactively sputtered molybdenum oxide films for solar cell application” H. Simchi, B.E. McCandless, T. Meng, J.H. Boyle, and W.N. Shafarman, Journal of Applied Physics, 114, 013503 (2013); doi.org/10.1063/1.4812587

“Electron drift-mobility measurements in polycrystalline CuIn1−xGaxSe2 solar cells” S. A. Dinca , E. A. Schiff , W. N. Shafarman, B. Egaas, R. Noufi, Applied Physics Letters 100, 103901 (2012); dx.doi.org/10.1063/1.3692165

“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); doi.org/10.1063/1.4704390

“Ga homogenization by simultaneous H2Se/H2S reaction of Cu-Ga–In precursor” Woo Kyoung Kim, Gregory M. Hanket, William N. Shafarman, Solar Energy Materials & Solar Cells 95, 235–238 (2011).

“The electronic structure of Cu(In1−xGax)Se2 alloyed with silver” Peter T. Erslev, JinWoo Lee, Gregory M. Hanket, William N. Shafarman, J. David Cohen, Thin Solid Films 519, 7296 (2011).

“Structural characterization of the (AgCu)(InGa)Se2 thin film alloy system for solar cells” J.H. Boyle, B.E. McCandless, G.M. Hanket, W.N. Shafarman, Thin Solid Films 519, 792-795 (2011).

“Metastable properties of Cu(In1−xGax)Se2 with and without sodium” Peter T. Erslev, William N. Shafarman, and J. David Cohen, Applied Physics Letters 98, 062105 (2011).􏰀

“Cu(In,Ga)Se2 Film Formation From Selenization of Mixed Metal/Metal-selenide Precursors,” Rui Kamada, William N. Shafarman and Robert W. Birkmire, Solar Energy Materials & Solar Cells 94, 451 (2010).

“Hole drift mobility measurements in polycrystalline CuIn1−xGaxSe2” S. A. Dinca, E. A. Schiff, B. Egaas, R. Noufi, and D. L. Young, W. N. Shafarman, Physical Review B 80, 235201 (2009).

“The influence of Na on metastable defect kinetics in CIGS materials” Peter T. Erslev, Jin Woo Lee, William N. Shafarman, J. David Cohen, Thin Solid Films 517, 2277 (2009).

“Understanding Defect-related Issues Limiting Efficiency of CIGS Solar Cells,” Matgorzata Igalson, Pawel Zabierowski, Daniel Przado, Aleksander Urganiak, Marika Edoff, William N. Shafarman, Solar Energy Materials & Solar Cells 93, 1290-1295 (2009).

“P-i-n Double-heterojunction Thin-film Solar Cell p-layer Assessment,” J.A. Spies, R. Schafer, J.F. Wager, P. Hersh, H.A.S. Platt, D.A. Keszler, G. Schneider, R. Kykyneshi, J. Tate, X. Lu, A.D. Compaan, W.N. Shafarman, Solar Energy Materials & Solar Cells 93, 1296-1308 (2009).

“Composition Control of Cu(InGa)(SeS)2 Deposited by Elemental Coevaporation,” Shiro Nishiwaki and William N. Shafarman, Journal of Applied Physics 104, 034912 (2008). doi.org/10.1063/1.2965191

“Development of CuInSe2 Nanocrystal and Nanoring Inks for Low-Cost Solar Cells”, Qiije Guo, Suk Jun Kim, Mahaprasad Kar, William N. Shafarman, Robert W. Birkmire, Eric A. Stach, Rakesh Agrawal and Hugh W. Hillhouse, NanoLetters 8, 2982 (2008).

“Depth-resolved band gap in Cu(In,Ga)(Se,S)2 thin films” M. Bär, S. Nishiwaki, L. Weinhardt, S. Pookpanratana, O. Fuchs, M. Blum W. Yang, J. D. Denlinger, W. N. Shafarman, and C. Heske, Applied Physics Letters 93, 244103 (2008).

“Incongruent Reaction of Cu-(InGa) Intermetallic Precursors in H2Se and H2S,” G.M. Hanket, W.N. Shafarman, B.E. McCandless and R.W. Birkmire, Journal of Applied Physics 102, 074823 (2007).

“Comparison of Device Performance and Measured Transport Parameters in Widely-Varying Cu(In,Ga)(Se,S) Solar Cells,” I. L. Repins, B. J. Stanbery, D.L. Young, S.S. Li, W.K. Metzger, C.L. Perkins,W.N. Shafarman, M.E. Beck, L. Chen, V.K. Kapur, D. Tarrant, M.D. Gonzalez, D.G. Jensen, T.J.Anderson, X. Wang, L.L. Kerr, B. Keyes, S. Asher, A. Delahoy and B Von Roedern, Progress in Photovoltaics 14, 25 (2006).

“Surface Sulfurization Studies of Cu(InGa)Se2 Thin Films,” Udai P. Singh, William N. Shafarman, Robert W. Birkmire, Solar Energy Mat. & Solar Cells 90, 623 (2006).

“Void Formation and Surface Energies in Cu(InGa)Se2,” C. Lei, A. Rockett, I.M. Robertson, W.N. Shafarman and M. Beck, Journal of Applied Physics 100, 073518 (2006).

“TiN and TiO2:Nb thin film preparation using hollow cathode sputtering with application to solar cells,” S.Y. Guo, W.N. Shafarman, A.E. Delahoy, J. Vac. Sci. Tech. A 24, 1524 (2006).

“Cu(InGa)Se2 Solar Cells on a Flexible Polymer Web,” R.W. Birkmire, E. Eser, S. Fields and W.N.

“Five-Source PVD for the Deposition of Cu(In1-xGax)(Se1-ySy)2 Absorber Layers,” M. Gossla and W.N. Shafarman, Thin Solid Films 480-481, 33 (2005).

“Bulk and Metastable defects in CuIn1-xGaxSe2 Thin Films Using Drive-Level Capacitance Profiling,” J.T. Heath, J.D. Cohen and W.N. Shafarman, Journal of Applied Physics 95, 1000 (2004); doi.org/10.1063/1.1633982

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