Degradation-related Defect Level in Weathered Silicon Heterojunction Modules Characterized by Deep Level Transient Spectroscopy

Commercial silicon heterojunction modules known as heterojunction with intrinsic (amorphous silicon) thin-film layer (HIT) modules show average degradation after 10 years in the field. HIT modules weathered outdoors in Colorado and Florida have reduced photoluminescence intensity compared to a control module and have degradation dominated by voltage loss. Deep level transient spectroscopy (DLTS) detects three electron-trap defect states in all modules with activation energies of 0.07, 0.16, and 0.50eV. DLTS on the weathered modules shows an additional deep-level, electron-trap defect state with an activation energy of 0.52eV.