M.S. Gillanders

Triple-junction GaInP/GaAs/Ge solar cells-production status, qualification results and operational benefits

In 1999 Spectrolab completed design and qualification, and began production on the next generation of multijunction solar cells-a triple-junction GaInP/GaAs/Ge. With over 20% AM0 conversion efficiency at an operating temperature of 60/spl deg/C, this cell provides 8-11% more power than competing dual-junction designs in GEO orbit after 15 years (6/spl times/10/sup 14/ 1-MeV electron equivalence). Spectrolab is currently qualifying an improved triple-junction cell capable of delivering over 22% AM0 conversion efficiency under these same conditions, with a beginning-of-life operating efficiency of 27%.

Production ready 30% efficient triple junction space solar cells

Spectrolab presents its next production GaInP/GaAs/Ge space triple junction solar cell, the XTJ space solar cell, averaging 29.8% efficiency at maximum power (AM0, 28°C, 135.3 mW/cm2) at beginning-of-life (BOL) testing of large populations (845 cells) of large-area solar cells without coverglass. Bare cells from this population with area of 26.62 cm2 have been tested to a maximum efficiency of 31.1% under the same AM0 testing. Additional optical and electrical performance characterization will be presented. XTJ is more than a BOL power improvement over heritage products. Bare cell radiation testing shows power retention at max power (NPmp) of 0.89 and 0.84 after irradiation with 1-MeV energy electrons to a fluence of 5e14 cm−2 and 1e15 cm−2, respectively. Environmental degradation testing of XTJ parts shows only 1.7% degradation for more than 4000 hours at 250°C and no degradation after 90 days at 95% r.h. and 45°C. Together these characteristics enable XTJ to be a 7% improvement in end-of-life cost of power on space flight panel over Spectrolabs 28% BOL efficient UTJ. Finally, XTJ engineering confidence thermal cycle testing and qualification status to the AIAA S-111-2005 standard will be elaborated.

Advancements in GaInP/sub 2//GaAs/Ge solar cells - production status, qualification results and operational benefits

In 2001 Spectrolab completed design and qualification, and began production on the third-generation multijunction solar cell - the improved triple-junction GaInP/sub 2//GaAs/Ge. With over 21% AMO conversion efficiency at an operating temperature of 60/spl deg/C at end-of-life, this cell has 16% more power than competing dual-junction designs in GEO orbit after 15 years (7/spl times/10/sup 14/ 1-MeV electron equivalence). Spectrolab is currently qualifying the fourth-generation triple-junction solar cell capable of delivering over 22% AMO conversion efficiency under these same conditions, with a beginning-of-life operating efficiency of 28%.

Production and qualification status of GaAs/Ge top/bottom contact solar cells

The status of top/bottom contact GaAs/Ge solar cell production is described. Over 3000 equivalent 2 cm*4 cm cells have been processed on the manufacturing line. The majority have been 2 cm*4 cm at 7.5 mils thick, but 4 cm*4 cm and 6 cm*6 cm cells have also been produced in thicknesses down to 3.5 mils. Flight program results are presented for UoSAT-F, and the current status of cells and panels built for the SAMPEX and PASP Plus programs is discussed.<<ETX>>

Ultra triple-junction high-efficiency solar cells

Solar cells suitable for the space environment must combine high-efficiency, high energy density, and radiation hardness in a manufacturable design. As improvement in one performance parameter usually results in degradation in one or more of the remaining parameters, careful optimization is required to enhance overall performance. The ultra triple-junction cell developed builds upon the established success of the fully qualified improved triple-junction cell currently in production. In the ultra triple-junction cell configuration, improved robustness and efficiency after radiation exposure augment a cell design expected to deliver 28% beginning-of-life efficiency in production.

Final qualification test results of XTJ triple junction space solar cell to AIAA - S-111 - 2005 and Spectrolab test standards

Spectrolab successfully completed the qualification of its latest and final triple junction space solar cell, 30% class XTJ (neXt Triple Junction), per AIAA S-111-2005 and Spectrolab test standards. The final qualification and characterization test results are presented in this paper. XTJ exhibits a 4.2 % power gain over Spectrolabs current space PV, UTJ, at both beginning of life and end of life. Moreover, nearly 3% lower solar absorptance of XTJ allows for a cooler operating temperature in a typical GEO mission. XTJ showed excellent front and backside welding contact integrities, insensitivity to ESDS, and negligible loss from humidity and GEO thermal cycle tests. Currently Spectrolabs large area XTJ (59.65cm2) is undergoing qualification per Spectrolab specified test standards.

Large area solar cells for future space power systems

Space silicon solar cell technology has matured to the extent that large-area planar silicon cells can be fabricated in sizes up to 8 cm*8 cm with efficiencies up to approximately 15%. In order to achieve substantially higher efficiencies, cells based on GaAs are required. It is shown that, subject to certain boundary conditions, the efficiency of GaAs/Ge cells can reach 24% when used in the dual-junction configuration or approximately 19.5% if the Ge substrate is passive. The electrooptical properties of these cells are reviewed, and prospects for achieving these efficiency goals are presented. Experimental performance data are given. >

The ultra triple-junction cell: high-efficiency solar cell for space applications

Solar cells suitable for the space environment must combine high efficiency, high energy density, and radiation hardness in a manufacturable design. As improvement in one performance parameter usually results in degradation in one or more of the remaining parameters, careful optimization is required to enhance overall performance. The ultra triple-junction cell developed by Spectrolab builds upon the established success of the fully qualified improved triple-junction cell currently in production. In the ultra triple-junction cell configuration, improved robustness and efficiency after radiation exposure augment a cell design that is expected to deliver 28% beginning-of-life efficiency in production.

Qualification status of 30% efficient next triple junction (XTJ) GaInP 2 /GaAs/Ge solar cells to AIAA S-111-2005 standard

Spectrolab presents the qualification status of its latest triple junction space solar cell, neXt Triple Junction (XTJ). The beginning of life efficiency averages 29.9% at maximum power (AM0, 28°C, 135.3 mW/cm2). The qualification in progress complies with the AIAA S-111-2005 standards for bare cell, CIC, and coupon level tests. Thermal cycle GEO coupons built for engineering confidence prior to the qualification showed excellent mechanical and electrical performance. Interim qualification status and test results are discussed.