Conductive Tin Oxide Under the Thermal Budget of Perovskite/TOPCon Tandems: Toward Indium‐Free Contacts

ABSTRACT The development of In‐free transparent conductive oxides (TCOs) is essential for sustainable photovoltaics. For undoped tin oxide (SnO x ), achieving high conductivity requires precise control over intrinsic defect chemistry. This work explores the impact of deposition pressure and oxygen stoichiometry on the electrical and optical properties of SnO x films grown by pulsed laser deposition (PLD). We identify a narrow conductivity window achieved at oxygen pressures between 0.015 and 0.020 mbar, beyond which a substantial drop in conductivity is observed. Within this optimal window, the SnO x films exhibit a 3‐fold mobility enhancement after 300°C air annealing, despite preserving an amorphous phase. This improvement is primarily attributed to the reduction of ionized impurity scattering, evidenced by a simultaneous decrease in free carrier density. To demonstrate functionality, the inherent soft‐landing nature of PLD was exploited to preserve the passivation quality of textured tunnel oxide passivating contacts (TOPCon) silicon substrates, as implied open‐circuit voltage (iV oc ) mapping confirmed the absence of deposition‐induced damage. Finally, we demonstrate the compatibility of this In‐free TCO by fabricating proof‐of‐concept perovskite solar cells on textured SnO x /n‐TOPCon substrates, achieving open‐circuit voltage of 1.21 V. These results highlight the potential of SnO x ​for integration as an interconnection layer in fully textured perovskite/Si tandem solar cells.