Enhanced passivation performance in n-type TOPCon solar cells via a novel deuteration/hydrogenation hybrid strategy

The advent of the passivating contact concept and its accelerated development have propelled crystalline silicon (c-Si) solar cells into a new era, establishing them as a driving force behind the latest breakthroughs in photovoltaic (PV) conversion efficiency. The continual refinement of passivation performance is pivotal to the fabrication of high-efficiency devices. Here, we report a novel deuteration/hydrogenation hybrid strategy involving the deliberate incorporation of deuterium (D, ²H) via atmosphere annealing to neutralize defects and enhance the passivation performance of tunnel oxide passivating contact (TOPCon) solar cells. Our findings reveal that hydrogen and deuterium can coexist within the TOPCon structure, where they exhibit a synergistic effect. Notably, when combined at an optimal ratio of 1% deuterium oxide (D₂O), this mixture significantly enhances passivation performance compared to the individual addition of hydrogen or deuterium. Specifically, it results in an approximate 15 mV increase in the implied open-circuit voltage (<em>iV</em>_OC) for double-sided passivated samples, achieving an average <em>iV</em>_OC value of 734 mV. The mechanisms underlying the enhancement in passivation can be inferred, suggesting that deuterium forms stronger bonds with silicon than hydrogen, effectively passivating interfaces and neutralizing defects within polycrystalline silicon (poly-Si). In the presence of dangling bonds on the poly-Si surface, the presence of H₂O molecules expands the range of silicon atoms in the vicinity of the contact site where electrons are exchanged or reacted with D₂O both horizontally and vertically, demonstrating enhanced adsorption capacity. Proof-of-concept TOPCon solar cells using this novel deuteration/hydrogenation hybrid strategy achieve a promising efficiency of 23.19%, accompanied by substantial improvements in electrical performance, thereby highlighting the exceptional potential of deuterium passivation for high-efficiency TOPCon solar cells.