Stress compensation based on interfacial nanostructures for stable perovskite solar cells

The long-term stability issue of halide perovskite solar cells hinders their commercialization. The residual stress–strain affects device stability, which is derived from the mismatched thermophysical and mechanical properties between adjacent layers. In this work, we introduced the Rb₂CO₃ layer at the interface of SnO₂/perovskite with the hierarchy morphology of snowflake-like microislands and dendritic nanostructures. With a suitable thermal expansion coefficient, the Rb₂CO₃ layer benefits the interfacial stress relaxation and results in a compressive stress–strain in the perovskite layer. Moreover, reduced nonradiative recombination losses and optimized band alignment were achieved. An enhancement of open-circuit voltage from 1.087 to 1.153 V in the resultant device was witnessed, which led to power conversion efficiency (PCE) of 22.7% (active area of 0.08313 cm²) and 20.6% (1 cm²). Moreover, these devices retained 95% of its initial PCE under the maximum power point tracking (MPPT) after 2700 h. It suggests inorganic materials with high thermal expansion coefficients and specific nanostructures are promising candidates to optimize interfacial mechanics, which improves the operational stability of perovskite cells.