WO2005088733-A1  A.W. BETT ET AL: 'III-V compounds for solar cell applications' APPLIED PHYSICS A vol. 69, 1999, pages 119 - 129, XP000886008;  ALVI N.S. ET AL: 'The potential for increasing the efficiency of photovoltaic systems by using multiple cell concepts' CONFERENCE RECORD OF THE 12TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE 1976, pages 948 - 956, XP002979527;  MURAYAMA ET AL: 'Light trapping in spherical silicon solar cell module' SOLAR ENERGY MATERIAL AND SOLAR CELLS vol. 79, 2003, pages 113 - 124, XP002979526;  See also references of EP 1724841A1EP1724841-A1  No further relevant documents disclosed;  See also references of WO 2005088733A1;  See references of WO 2005088733A1US9159856-B2  Murayama et al., "Light trapping in spherical silicon solar cell module", Solar Energy Material & Solar Cells, vol. 79, (2003), pp. 113 to 124.;  A.W. Bett et al., "III-V compound for solar cell applications", Applied Physics A, vol. 69 (1999), pp. 119 to 129.;  N.S. Alvi et al., "The Potential for Increasing the Efficiency of Photovoltaic Systems Using Multiple Cell Concepts", Conference Record of 12th IEEE Photovoltaic Specialists Conference, 1976, pp. 948 to 956.EP1724841-B1  A. W. Bett, F. Dimroth, G. Stollwerck, O. V. Sulima "III - V Compounds For Solar Cell Applications" Appl. Phys. A69, 119 - 129 (1999;  High-Efficiency III-V Multijunction Solar Cells" in: Handbook of Photovoltaic Science and Engineering; 359-412;  OLSON ET AL: "Chapter 9: High-efficiency III-V miltujunction solar cells", 1 January 2003, HANDBOOK OF PHOTOVOLTAIC SCIENCE AND ENGINEERING, JOHN WILEY & SONS, CHICHESTER [U.A.], PAGE(S) 359 - 412, ISBN: 978-0-471-49196-5, XP009183315;  ALVI N S ET AL: "The potential for increasing the efficiency of photovoltaic systems by using multiple cell concepts", 1 January 1996, CONFERENCE RECORD OF THE 25TH. IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE 1996. WASHINGTON, MAY 13 - 17, 1996; [CONFERENCE RECORD OF THE IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE], NEW YORK, IEEE, US, PAGE(S) 948 - 956, ISBN: 978-0-7803-3167-9, XP002979527