Electron Irradiation-Induced Degradation of SHJ Solar Cells with Low-Cost Mass Production Towards the Low Earth Orbit Constellations Application

Silicon solar cells are currently expected to resume into the space market especially for the low earth orbit constellations in the dawning commercial spaceflight industry throughout the world. In this paper, the commercial p-type wafers are used, and the front emitter silicon heterojunction (SHJ) solar cells with 100 mu m thickness are prepared. These cells are treated with 1 MeV electron irradiation of various fluence. The degradation performances of SHJ cells are analyzed, it is found that the degradation rates of the SHJ cell efficiency are around 22.5% and 26.6% at 5.0 & times; 1013 and 1.0 & times; 1014 e/cm2, respectively, which is mainly attributed to the open-circuit voltage degradation. Furthermore, the deep level transient spectroscopy (DLTS) measurements indicated that the high concentration defects at the deep levels of EV + 0.36 eV and EV + 0.18 eV within energy band of the crystalline silicon act as the traps and recombination centers to deteriorate the carrier diffusion length and the open-circuit voltage of the irradiated SHJ solar cells. Fortunately, 96 h-light soaking under AM0 at room temperature and further 20-min annealing treatment at 150 degrees C in open circuit condition under nitrogen allows SHJ solar cells to create a recovery, and the degradation rates come down to around 18.6% and 23.2% with the electron irradiation fluences of 5.0 & times; 1013 and 1.0 & times; 1014 e/cm2 at 1 MeV, respectively. In fact, this post-treatment process is similar to the on-orbit operating state of a satellite, the solar cells temperature would sharply increase when solar panels face the sun. This self-healing can partially mitigate the radiation-induced degradation of SHJ solar cell.