Reliability testing of large area 3J space solar cells

Multijunction solar cells have been a key enabler to Space Satellites in the past decade. Spectrolab has made major capital investment to improve the performance of the solar cells (W/m2) and reduce cost ($/W). The W/m2 improvement has been achieved by improving the efficiency of the solar cells (e.g. XTJ cell). The 29.5% efficiency XTJ cell has been qualified to AIAA-S-111–2005 standard. The $/W reduction has been achieved by qualifying the large format of the cells (e.g. UTJ and XTJ “LEONE”). The dimensions of the LEONE cells (53.3 cm2 to 59.65 cm2), also referred to as “1 per” cells, have been optimized to maximize utilization of the 100 mm wafer and achieve panel packing efficiency equal to or close to the heritage “2 per” cells from 100 mm wafer (26 cm2–32 cm2). UTJ LEONE cells are in orbit on board multiple LEO communication satellites. Insertion of these cell technologies followed a very rigorous qualification and reliability testing at cell, CIC and coupon level to mitigate any risk associated with the large area cell. The LEONE UTJ cell qualification program included thermo mechanical testing to 66,060 LEO and 15,549 GEO thermal cycles on multiple coupons; and radiation testing on bare cells. Inverted and normal gradient ESD testing was performed on CICs and multiple coupons to mitigate potential risk with use of large area cells on high voltage arrays. The ESD testing on coupons was performed up to a differential voltage of 130V at 1.2 A without occurrence of any permanent sustained arcs. To further reduce the $/W, Spectrolab is now transitioning to the 150 mm wafer fab line leading to the insertion of the 72.44 cm2 XTJ “SuperCell” in the 3rd quarter of 2012. This presentation will discuss the details of the qualification and reliability tests and test results on LEONE cells. The presentation will also discuss the qualification test and insertion plan for the XTJ SuperCell.