A comparative study of Cd‐ and Zn‐compound buffer layers on Cu(In1−x,Gax)(Sy,Se1−y)2 thin film solar cells

This paper reports a comparative study of Cu(In,Ga)(S,Se)2 (CIGSSe) thin‐film solar cells with CBD‐CdS, CBD‐ZnS(O,OH) and ALD‐Zn(O,S) buffer layers. Each buffer layer was deposited on CIGSSe absorber layers which were prepared by sulfurization after selenization (SAS) process by Solar Frontier K. K. Cell efficiencies of CBD‐CdS/CIGSSe, CBD‐ZnS(O,OH)/CIGSSe and ALD‐Zn(O,S)/CIGSSe solar cells exceeded 18%, for a cell area of 0.5 cm2. The solar cells underwent a heat‐light soaking (HLS) post‐treatment at 170 °C under one‐sun illumination in the air; among the three condtions, the ALD‐Zn(O,S)/CIGSSe solar cells showed the highest cell efficiency of 19.78% with the highest open‐circuit voltage of 0.718 V. Admittance spectroscopy measurements showed a shift of the N1 defect's energy position toward shallower energy positions for ALD‐Zn(O,S)/CIGSSe solar cells after HLS post‐treatment, which is in good agreement with their higher open‐circuit voltage and smaller interface recombination than that of CBD‐ZnS(O,OH)/CIGSSe solar cells. Copyright © 2015 John Wiley & Sons, Ltd.

[1]  T. Nakada,et al.  Post-treatment effects on ZnS(O,OH)/Cu(In,Ga)Se2 solar cells deposited using thioacetamide-ammonia based solution , 2014 .

[2]  T. Nakada,et al.  Thin-Film Solar Cells , 2002 .

[3]  L. Gedvilas,et al.  Cu(In,Ga)Se2 thin-film solar cells with ZnS(O,OH), Zn–Cd–S(O,OH), and CdS buffer layers , 2005 .

[4]  A. Zunger,et al.  Defect physics of the CuInSe 2 chalcopyrite semiconductor , 1998 .

[5]  T. Nakada,et al.  Effects of combined heat and light soaking on device performance of Cu(In,Ga)Se2 solar cells with ZnS(O,OH) buffer layer , 2014 .

[6]  D. Hariskos,et al.  New reaction kinetics for a high‐rate chemical bath deposition of the Zn(S,O) buffer layer for Cu(In,Ga)Se2‐based solar cells , 2012 .

[7]  Lars Stolt,et al.  Zn(O,S) buffer layers by atomic layer deposition in Cu(In,Ga)Se2 based thin film solar cells: Band alignment and sulfur gradient , 2006 .

[8]  T. Nakada.  Diffusion Behavior and Microstructural Properties of the CBD-ZnS/CIGS Interface Boundary , 2001 .

[9]  U. Rau,et al.  Compositional trends of defect energies, band alignments, and recombination mechanisms in the Cu(In,Ga)(Se,S)2 alloy system , 2003 .

[10]  H. Schock,et al.  Influence of the Ga-content on the bulk defect densities of Cu(In,Ga)Se2 , 2001 .

[11]  T. Nakada,et al.  Efficient Cu(In,Ga)Se2 thin film solar cells with reduced thickness of ZnS(O,OH) Buffer Layer , 2013 .

[12]  Daniel Lincot,et al.  Buffer layers and transparent conducting oxides for chalcopyrite Cu(In,Ga)(S,Se)2 based thin film photovoltaics: present status and current developments , 2010 .

[13]  Debora Keller,et al.  Potassium-induced surface modification of Cu(In,Ga)Se2 thin films for high-efficiency solar cells. , 2013, Nature materials.

[14]  T. Nakada,et al.  18% Efficiency Cd-Free Cu(In, Ga)Se2 Thin-Film Solar Cells Fabricated Using Chemical Bath Deposition (CBD)-ZnS Buffer Layers , 2002 .

[15]  C. Rincón,et al.  Defect physics of the CuInSe2 chalcopyrite semiconductor , 1999 .

[16]  U. Rau,et al.  Composition dependence of defect energies and band alignments in the Cu(In1−xGax)(Se1−ySy)2 alloy system , 2002 .

[17]  Dimitrios Hariskos,et al.  CIGS Solar Cells with Efficiencies > 20 %: Current Status and New Developments , 2011 .

[18]  Andreas Bauer,et al.  Properties of Cu(In,Ga)Se2 solar cells with new record efficiencies up to 21.7% , 2015 .

[19]  T. Nakada,et al.  Impacts of Post-Treatments on Cell Performance of CIGS Solar Cells With Zn-Compound Buffer Layers , 2013, IEEE Journal of Photovoltaics.

[20]  M. Edoff,et al.  Experimental investigation of Cu(In1−x,Gax)Se2/Zn(O1−z,Sz) solar cell performance , 2011 .

[21]  Yoshiyuki Chiba,et al.  Achievement of 19.7% efficiency with a small-sized Cu(InGa)(SeS)2 solar cells prepared by sulfurization after selenizaion process with Zn-based buffer , 2013, 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC).

[22]  T. Nakada,et al.  Impacts of surface sulfurization on Cu(In1−x,Gax)Se2 thin‐film solar cells , 2015 .

[23]  T. Nakada,et al.  A Comparative Study of Heat-Light Soaking Effect on CIGS Thin Film Solar Cells with Zinc Compound Buffer Layers Deposited by ALD and CBD Processes , 2013 .

[24]  D. Hariskos,et al.  Compositional investigation of potassium doped Cu(In,Ga)Se2 solar cells with efficiencies up to 20.8% , 2014 .

[25]  T. Nakada,et al.  Comparison of Cell Performance of ZnS(O,OH)/CIGS Solar Cells With UV-Assisted MOCVD-ZnO:B and Sputter-Deposited ZnO:Al Window Layers , 2013, IEEE Journal of Photovoltaics.

[26]  A. Uhl,et al.  Comparison of ZnS-based Buffer Layers by Chemical Bath Deposition and Atomic Layer Deposition , 2009 .

[27]  Marika Edoff,et al.  Cadmium-free CIGS mini-modules with ALD-grown Zn(O, S)-based buffer layers , 2006 .

[28]  T. Nakada,et al.  Wide-Gap Cu(In,Ga)Se2 Solar Cells with Zn(O,S) Buffer Layers Prepared by Atomic Layer Deposition , 2012 .

[29]  T. Nakada,et al.  Effects of post-deposition treatments on transparent conducting ZnO:B thin films grown by MOCVD , 2014 .

[30]  S. Kijima,et al.  Achievement of 17.5% efficiency with 30 × 30cm2-sized Cu(In,Ga)(Se,S)2 submodules , 2012, 2012 38th IEEE Photovoltaic Specialists Conference.

[31]  K. Kushiya,et al.  Stabilization of PN Heterojunction between Cu(InGa)Se2 Thin-Film Absorber and ZnO Window with Zn(O, S, OH)x Buffer , 2000 .

[32]  R. Herberholz,et al.  Determination of defect distributions from admittance measurements and application to Cu(In,Ga)Se2 based heterojunctions , 1996 .

[33]  T. Nakada,et al.  ZnO/ZnS(O,OH)/Cu(In,Ga)Se*~o SOLAR CELL WITH 18:6% EFFICIENCY , 2003 .

[34]  T. Nakada,et al.  Modeling of the surface sulfurization of CIGSe-based solar cells , 2014 .

[35]  T. Nakada,et al.  Cu(In,Ga)Se2 thin film solar cells with a combined ALD-Zn(O,S) buffer and MOCVD-ZnO:B window layers , 2013 .

[36]  W. Warta,et al.  Solar cell efficiency tables (version 36) , 2010 .

[37]  Motoshi Nakamura,et al.  Recent R&D progress in solar frontier's small-sized Cu(InGa)(SeS)2 solar cells , 2014, 2014 IEEE 40th Photovoltaic Specialist Conference (PVSC).

[38]  D. Lincot,et al.  The Zn(S,O,OH)/ZnMgO buffer in thin‐film Cu(In,Ga)(Se,S)2‐based solar cells part II: Magnetron sputtering of the ZnMgO buffer layer for in‐line co‐evaporated Cu(In,Ga)Se2 solar cells , 2009 .