Post-Separation Processing for Silicon Heterojunction Half Solar Cells With Passivated Edges

We investigate different postseparation process routes for silicon heterojunction (SHJ) half solar cells, separated by thermal laser separation. SHJ half cells with and without aluminum oxide (Al₂O₃) deposition as edge passivation layer undergo different annealing processes, including i) a hotplate; ii) an inline oven; and iii) an ultrafast light soaking process. SHJ half cells with an initial efficiency of 21.7% reach 21.9% after Al₂O₃ deposition and inline oven annealing (pseudo fill factor, pFF, increase of 0.3%_abs and series resistance R_S decrease by −0.05 Ωcm²). The light soaking process is known to lead to improved surface passivation and carrier transport for SHJ cells. For light soaking processed SHJ half cells, an 21.9% efficiency is obtained (R_S reduction by −0.13 Ωcm² and open-circuit voltage V_OC increase by +2 mV compared to the initial half cell). By combining Al₂O₃ deposition and subsequent light soaking, SHJ half cells reach 22.1% efficiency, resulting from the combined benefits for pFF, R_S, and V_OC of the two processes. No additional thermal annealing of the Al₂O₃ layer is necessary, proving that the light soaking process is sufficient to activate the Al₂O₃ passivation. This allows for a two-step postseparation process sequence, resulting in SHJ half cells featuring similar efficiencies to light soaking processed full cells. SHJ half cells, integrated into one-cell modules after Al₂O₃ deposition and light soaking, show an efficiency advantage of +0.3%_abs in comparison to modules with untreated half cells. Thus, we demonstrate the possibility of compensating separation losses for SHJ half cells and the transferability of the improvements to module level.