Abstract
This paper details 3-years of cadmium telluride (CdTe) photovoltaic performance onboard the AlSat-
1N CubeSat in low earth orbit. These are the first CdTe solar cells to yield I-V measurements from
space and help to strengthen the argument for further development of this technology for space
application. The data has been collected over some 17,000 orbits by the CubeSat with the cells
showing no signs of delamination, no deterioration in short circuit current or series resistance. The
latter indicating that the aluminium-doped zinc oxide transparent front electrode performance
remained stable over the duration. Effects of temperature on open circuit voltage (Voc) were observed
with a calculated temperature coefficient for Voc of -0.19 %/⁰C. Light soaking effects were also
observed to increase the Voc. The fill factor decreased over the duration of the mission with a major
contribution being a decrease in shunt resistance of all 4 of the cells. The decrease in shunt resistance
is speculated to result from gold diffusion from the rear contacts into the absorber and through to the
front interface. This has likely resulted in the formation of a deep trap state within the CdTe and
micro-shunts formed between the rear and front contact. Further development of this technology
should therefore utilise more stable back contacting methodologies more commonly employed for
terrestrial CdTe modules.