Green solvent enabled scalable processing of perovskite solar cells with high efficiency

Perovskite solar cells (PSCs) have emerged as a promising next-generation photovoltaic technology for the future energy supply owing to their high efficiency, favourable solution processability and low cost. To accelerate their market entry, however, sustainability challenges remain to be cleared, particularly due to the heavy use of volatile and toxic organic solvents such as the mixture of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), which becomes even more problematic in mass production. Here we report eco-friendly biomass-derived green solvents with γ-valerolactone (GVL) and n-butyl acetate that allow for solution-based fabrication of high-quality FAPbI3 (FA, formamidinium) perovskite. Remarkably, the FAPbI3 perovskite ink remains stable for up to one year as a result of the high-valence [PbIx]2−x complexes and the strong interaction between GVL and FA+, which overcomes the otherwise instability of FA+ cations when DMF and DMSO are used. Equally important, upon further defect passivation engineering, our solar cells deliver a power conversion efficiency as high as 25.09%. Scaling up this green solvent method yields a mini-module with an aperture area of 12.25 cm2 that reaches a certified efficiency up to 20.23%, suggesting that our work has opened a sustainable pathway towards the practical application of this renewable energy technology.