Conformal oxides decouple chemical stability and energetics at NiO_x/perovskite interfaces

Nickel oxide (NiO_x) is a common hole transport layer (HTL) in perovskite photovoltaics, but the chemical reactivity of NiOx surfaces accelerates degradation when contacting perovskites. We developed an ultrathin, conformal tin oxide (SnO_x) interlayer to suppress interfacial reactivity between NiO_x and perovskite. SnO_x is typically an electron transport layer, but we show that the energy alignment can be modified for hole extraction using molecules with dipoles. This synergy yielded high efficiency in perovskite photovoltaic devices and showed an ~10x improvement in T90 lifetime in open-circuit conditions under AM1.5G at 65°C. This structure also improves resilience to thermomechanical durability, as minimodules retained 95.7% of their initial performance after 1000 thermal cycles (-65° to 85°C), highlighting the importance of interfaces for robust perovskite photovoltaic modules.