Investigation of Tin Oxide Atomic Layer Deposition on the Performance of Evaporated Perovskite Solar Cells

Although tin oxide (SnO_x) layers grown using atomic layer deposition (ALD) are routinely employed in p-i-n perovskite solar cells (PSCs), the correlation between ALD process parameters, SnO_x film properties, and PSC performance remains insufficiently investigated. This work examines the role of co-reactants, H₂O and H₂O₂, and their doses in influencing SnO_x material properties and the performance of evaporated p-i-n PSCs. H₂O₂-SnO_x exhibits higher film density and higher electron affinity compared to H₂O-SnO_x; however, PSCs incorporating H₂O-SnO_x demonstrate superior performance. The performance of PSCs containing H₂O₂-SnO_x is limited by an undesired chemical interaction between H₂O₂ and the underlying structure, which can be mitigated by employing a thin layer of H₂O-SnO_x prior to the deposition of H₂O₂-SnO_x on top of the perovskite/C₆₀ structure. Furthermore, the H₂O dose used during the ALD of SnO_x substantially affects PSC performance. High H₂O dose-SnO_x yields the highest power conversion efficiency (19%), whereas low H₂O dose-SnO_x results in the lowest efficiency (11.3%). Low H₂O dose-SnO_x exhibits low film density and excess ligand impurities, which can act as charge traps and introduce transport barrier when incorporated into PSCs. Therefore, high H₂O doses are indispensable during ALD of SnO_x to achieve efficient PSC performance.