EP848432-A2  BEAUMONT, B. ET AL.: 'A Four-Cell Photovoltaic System Based on InP and GaAs' 16TH LE.E.E. PHOTOVOLTAIC SPECIALISTS, SEPTEMBER 1982, pages 595 - 600;  DAVIES ET AL.: 'Calculations of efficiencies achievable using gallium arsenide and silicon cells mounted together in cavities illuminated by single-stage concentration' SOLAR ENERGY MATERIALS AND SOLAR CELLS vol. 26, 1992, pages 203 - 215;  J.C.C. FAN ET AL.: 'Optimal Design of High-Efficiency Tandem Cells' PROCEEDINGS OF THE 16TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE 1982, pages 692 - 704;  M.W. WANLASS ET AL.: 'Development of High-Performance GaInAsP Solar Cells for Tandem Solar Cell Applications' PROCEEDINGS OF THE 21ST IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE 1990, pages 172 - 178;  P.K. CHIANG: 'Large Area GaInp2/GaAs/Ge Multijunction Solar Cells for Space Applications' PROCEEDINGS OF LST WCPEC 1994, pages 2120 - 2123;  P.K. CHIANG: 'Large Area GaInp2GaAsGe Multijunction Solar Cells for Space Applications' PROCEEDINGS OF LST WCPEC 1994, pages 2120 - 2123;  S. KURTZ ET AL.: '19.6% Electron-Irradiated GaInP/GaAs Cells' PROCEEDINGS OF LST WCPEC (WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION 1994, pages 2108 - 2111;  S. KURTZ ET AL.: '19.6% Electron-Irradiated GaInPGaAs Cells' PROCEEDINGS OF LST WCPEC (WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION 1994, pages 2108 - 2111;  PATENT ABSTRACTS OF JAPAN vol. 010, no. 224 (E-425), 5 August 1986 & JP 61 059884 A (NEC CORP), 27 March 1986;  BEAUMONT B. ET AL.: "A Four-Cell Photovoltaic System based on InP and GaAs" SIXTEENTH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE-1982 , 27 - 30 September 1982, pages 595-600, XP002082165 San Diego, U.S.;  DAVIES P A ET AL: "CALCULATIONS OF EFFICIENCIES ACHIEVABLE USING GALLIUM ARSENIDE AND SILICON CELLS MOUNTED TOGETHER IN CAVITIES ILLUMINATED BY SINGLE-STAGE CONCENTRATION" SOLAR ENERGY MATERIALS AND SOLAR CELLS, vol. 26, no. 3, 1 April 1992, pages 203-215, XP000274201US5902417-A  Beaumont, B., et al. "A Four-Cell Photovoltaic System Based on InP and GaAs" Sixteenth IEEE Photovoltaic Specialists, Sep. (1982) pp. 595-600.;  Chiang et al., "Large Area GaInP2GaAsGe Multijunction Solar Cells For Space Applications", First WPCEC, Hawaii, Dec. 5-9, 1994, pp. 2120-2123.;  Davies, P., et al. "Calculations of Efficiencies Achievable Using Gallium Arsenide and Silicon Cells Mounted Together in Cavities Illuminated by Single-Stage Concentration" Solar Energy Materials and Solar Cells, vol. 26, No. 3, Apr. (1992) pp. 203-215.;  Fan, et al., "Optimal Design of High-Efficiency Tandem Cells", 16th IEEE Photovoltaic Specialists Conference, 1982, pp. 692-701.;  Kurtz et al., "19.6% Electron-Irradiated GaInPGasAs Cells", First WCPEC, Hawaii, Dec. 5-9, 1994, pp. 2108-2111.;  Theodore G. Stern, Proceedings 18th IECEC, Orlando, Fl, pp. 1334-1338, Aug. 1983.;  Wanlass et al., "Development of High-Performance GaInAsP Solar Cells For Tandem Solar Cell Applications", Proceedings of the 21st IEEE Photovoltaic Specialists, Conference, 1990, pp. 172-178.EP848432-B1  BEAUMONT B. ET AL.: "A Four-Cell Photovoltaic System based on InP and GaAs" SIXTEENTH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE-1982 , 27 - 30 September 1982, pages 595-600, XP002082165 San Diego, U.S.;  DAVIES P A ET AL: "CALCULATIONS OF EFFICIENCIES ACHIEVABLE USING GALLIUM ARSENIDE AND SILICON CELLS MOUNTED TOGETHER IN CAVITIES ILLUMINATED BY SINGLE-STAGE CONCENTRATION" SOLAR ENERGY MATERIALS AND SOLAR CELLS, vol. 26, no. 3, 1 April 1992, pages 203-215, XP000274201;  PATENT ABSTRACTS OF JAPAN vol. 010, no. 224 (E-425), 5 August 1986 & JP 61 059884 A (NEC CORP), 27 March 1986