Thin, lightweight, 18% efficient space silicon solar cell and array

The purpose of this paper is to report the progress achieved in the transition-to-production of the radiation hardened high efficiency silicon (RHHES) solar cell first introduced in 1993. The RHHES cell has a back-junction point-contact structure which has demonstrated higher than 18% AMO efficiency. Two major improvements were accomplished: a) scaling up the cell from a laboratory prototype size to one suitable for space applications; b) optical matching of the cover glass to the light trapping structure of the cell surface. In order to accommodate the larger cell size, it was necessary to completely re-design the junction and metalization patterns to increase production yields to acceptable and usable levels. To accomplish this, the junction area was increased with a corresponding decrease in metal periphery. All solar cells for space applications must be glassed to protect the cell from damage from proton radiation, micrometeorites, and handling. The glassing process is critical to the RHHES cell due to the fact that the bare cell surface depends, to some extent, on a light trapping textured structure to improve efficiency. Even with the best optically matched adhesives, some loss of output power was observed. After optimization of anti-reflective (AR) coatings, adhesive properties and application processes, more than 97% of the original power generating capability of the cell was retained.