Damp Heat and Light and Elevated Temperature Induced Degradation of TOPCon: Characterization and Modeling of Defect Generation in Amorphous Aluminum Oxide

Recent works have identified UV-induced degradation as a leading cause of significant power losses in tunnel oxide passivated contact (TOPCon) architectures, however, damp heat, light, and elevated temperature are also stressors of concern in fielded TOPCon modules. This work presents the results of accelerated aging studies probing damp heat induced degradation (DHID) and light and elevated temperature induced degradation (LeTID) of encapsulated TOPCon 1x1 and 2x2 minimodules. The 2x2 minimodules were pre-conditioned with damp heat or light and elevated temperature accelerated exposures before fielding. Preliminary results show greater VOC losses in TOPCon minimodules relative to silicon heterojunction minimodules after preconditioning. Glow discharge optical emission spectroscopy (GD-OES) was used to examine the chemical changes through depth as a function of external stressors in aged and unaged samples. Results show that even small changes in hydrogen distribution and passivation layer morphology due to accelerated aging can be captured. External radiative efficiency (ERE) measurements show significant losses in iVOC after accelerated aging, indicating degradation in the cell passivation. Ab initio molecular dynamics simulations of the bulk amorphous aluminum oxide passivation layer illustrate the importance of stoichiometry and density on H movement through the structure. In conjunction with GD-OES and ERE, these results suggest morphological changes in passivation due to accelerated aging that impact H movement in addition to passivation quality. Simulations of H movement and defect generation in bulk am-Al2O3 films will inform further characterization, culminating in structural simulation of the c-Si/am-Al2O3 interface.