Advanced light management based on periodic textures for Cu(In,Ga)Se2 thin-film solar cells.

We have used 3-D optical modelling to investigate light management concepts based on periodic textures and material optimization for photovoltaic devices based on Cu(In,Ga)Se2 (CIGS) absorber material. At first, calibration of the software based on the characterization of a reference (1500-nm thick) CIGS device was carried out. The effects of 1-D and 2-D symmetric gratings on the cell were then investigated, showing significant improvement in anti-reflection effect and in absorptance in the active layer, achieved by excitation of guided modes in the absorber. In addition, device configurations endowed with alternative back reflector and front transparent conductive oxide (TCO) were tested with the goal to quench parasitic absorption losses at front and back side. The use of In2O3:H (IOH) as front and back TCO, combined with an optimized 2-D grating structure, led to a 25% increase of the optical performance with respect to an equally-thick flat device. Most of the performance increase was kept when the absorber thickness was reduced from 1500 nm to 600 nm.

[1]  M. Zeman,et al.  Modelling of thin-film silicon solar cells , 2013 .

[2]  E. Yablonovitch.  Statistical ray optics , 1982 .

[3]  P. A. van Nijnatten.  An automated directional reflectance/transmittance analyser for coating analysis , 2003 .

[4]  W. Shafarman,et al.  Direct current-voltage measurements of the Mo/CuInSe/sub 2/ contact on operating solar cells , 1996, Conference Record of the Twenty Fifth IEEE Photovoltaic Specialists Conference - 1996.

[5]  Katsumi Kushiya,et al.  CIS-based thin-film PV technology in solar frontier K.K. , 2014 .

[6]  Miro Zeman,et al.  Ambiguities in optical simulations of nanotextured thin-film solar cells using the finite-element method. , 2015, Optics express.

[7]  S. Niki,et al.  Cu(In,Ga)Se2 Solar Cells With Amorphous Oxide Semiconducting Buffer Layers , 2015, IEEE Journal of Photovoltaics.

[8]  Isabelle Gerard,et al.  Broadband light-trapping in ultra-thin nano-structured solar cells , 2013, Photonics West - Optoelectronic Materials and Devices.

[9]  J. Springer,et al.  Absorption loss at nanorough silver back reflector of thin-film silicon solar cells , 2004 .

[10]  S. Krishnakumar,et al.  Electrical and optical properties of molybdenum trioxide thin films , 1993 .

[11]  M. Kondo,et al.  Enhanced photocurrent and conversion efficiency in thin-film microcrystalline silicon solar cells using periodically textured back reflectors with hexagonal dimple arrays , 2012 .

[12]  H. Fujiwara,et al.  Hydrogen-doped In2O3 as High-mobility Transparent Conductive Oxide , 2007 .

[13]  S. Niki,et al.  Quantitative Assessment of Optical Gain and Loss in Submicron-TexturedCuIn1−xGaxSe2Solar Cells Fabricated by Three-Stage Coevaporation , 2014 .

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

[15]  N. Kohara,et al.  Chemical and Structural Characterization of Cu(In,Ga)Se2/Mo Interface in Cu(In,Ga)Se2 Solar Cells , 1996 .

[16]  P. Babál,et al.  Micro-textures for efficient light trapping and improved electrical performance in thin-film nanocrystalline silicon solar cells , 2013 .

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

[18]  Hiroyuki Fujiwara,et al.  Effects of carrier concentration on the dielectric function of ZnO:Ga and In 2 O 3 : Sn studied by spectroscopic ellipsometry: Analysis of free-carrier and band-edge absorption , 2005 .

[19]  J. Krč,et al.  Modeling plasmonic scattering combined with thin-film optics , 2011, Nanotechnology.

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

[21]  Diego Caratelli,et al.  3‐D optical modeling of thin‐film silicon solar cells on diffraction gratings , 2013 .

[22]  Christophe Ballif,et al.  UV‐nano‐imprint lithography technique for the replication of back reflectors for n‐i‐p thin film silicon solar cells , 2011 .

[23]  The potential of textured front ZnO and flat TCO/metal back contact to improve optical absorption in thin Cu(In,Ga)Se2 solar cells , 2007 .

[24]  Jürgen H. Werner,et al.  Alternative back contact materials for thin film Cu(In,Ga)Se2 solar cells , 2003 .

[25]  Zongfu Yu,et al.  Fundamental limit of light trapping in grating structures. , 2010, Optics express.

[26]  Miro Zeman,et al.  Full‐wave optoelectrical modeling of optimized flattened light‐scattering substrate for high efficiency thin‐film silicon solar cells , 2014 .

[27]  J. van Deelen,et al.  A study on the optics of copper indium gallium (di)selenide (CIGS) solar cells with ultra-thin absorber layers. , 2014, Optics express.

[28]  M. Zeman,et al.  Enhancing the driving field for plasmonic nanoparticles in thin-film solar cells. , 2014, Optics express.

[29]  J. Krč,et al.  Stability of plasmonic metal nanoparticles integrated in the back contact of ultra-thin Cu(In,Ga)S2 solar cells , 2013 .

[30]  C. Ballif,et al.  Improving metal reflectors by suppressing surface plasmon polaritons: a priori calculation of the internal reflectance of a solar cell , 2013, Light: Science & Applications.

[31]  H. Fujiwara,et al.  Reduction of Optical Loss in Hydrogenated Amorphous Silicon/Crystalline Silicon Heterojunction Solar Cells by High-Mobility Hydrogen-Doped In2O3 Transparent Conductive Oxide , 2008 .

[32]  M. Zeman,et al.  Extraction of optical properties of flat and surface-textured transparent conductive oxide films in a broad wavelength range , 2011 .

[33]  J. Sites,et al.  Potential of submicrometer thickness Cu(In,Ga)Se2 solar cells , 2005 .

[34]  Shanhui Fan,et al.  Light management for photovoltaics using high-index nanostructures. , 2014, Nature materials.

[35]  F. Ducroquet,et al.  Characteristics of molybdenum bilayer back contacts for Cu(In,Ga)Se2 solar cells on Ti foils , 2013 .

[36]  Martina Schmid,et al.  Light Coupling and Trapping in Ultrathin Cu(In,Ga)Se2 Solar Cells Using Dielectric Scattering Patterns. , 2015, ACS nano.