Dopant-additive synergism enhances perovskite solar modules.

Perovskite solar cells (PSCs) are among the most promising photovoltaic technologies due to their exceptional optoelectronic properties 1,2 . However, the lower efficiency, poor stability, and reproducibility issues of large-area PSCs compared to laboratory-scale PSCs are major drawbacks that hinder their commercialisation 3 . Here we report a synergistic dopant-additive combination strategy using methylammonium chloride (MACl) as the dopant and a Lewis-basic ionic-liquid additive, 1,3-bis(cyanomethyl)imidazolium chloride ([Bcmim]Cl). This strategy effectively inhibits the degradation of the perovskite precursor solution (PPS), suppresses the aggregation of MACl, and results in phase-homogeneous and stable perovskite films with high crystallinity and less defects. This approach enabled the fabrication of perovskite solar modules (PSMs) that achieved a certified efficiency of 23.30% and ultimately stabilised at 22.97% over a 27.22 cm 2 aperture area, marking the highest certified PSM performance. Additionally, the PSMs displayed long-term operational stability, maintaining 94.66% of the initial efficiency after 1000 h under continuous one-sun illumination at room temperature. The interaction between [Bcmim]Cl and MACl was extensively studied to unravel the mechanism leading to an enhancement of device properties. Our approach holds significant promise for bridging the benchtop-to-rooftop gap and advancing the production and commercialisation of large-area perovskite photovoltaics.