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All-inorganic β-CsPbI 3 has superior chemical and thermal stability compared to its hybrid counterparts, but the stability of state-of-the-art β-CsPbI 3 perovskite solar cells (PSCs) under normal operating conditions (i.e., under illumination in an inert atmosphere) remains inferior to their hybrid counterparts. Here, we found that the lattice distortion in CsPbI 3 near the perovskite/electron transport layer (ETL) interface can induce polymorphic transformation in encapsulated CsPbI 3 films aged under illumination. To suppress this lattice distortion, we introduced alkyltrimethoxysilane strain-release layers (SRLs) at the perovskite/ETL interface. We found the SRL with the longest alkyl chain is the most effective at reducing interfacial lattice distortion, leading to enhanced charge transfer at the perovskite/ETL interface and improved phase/device stability. Its incorporation in β-CsPbI 3 solar cells resulted in a power-conversion efficiency of 20.1% and an operational lifetime with an extrapolated T 80 of >3000 h for encapsulated devices tested under continuous illumination under maximum power point tracking conditions.
Liu et al. (Thu,) studied this question.