Ambient Gas-Quenching Fabrication of MA-Free Perovskite Solar Cells Enabled by an Eco-Friendly Urea Additive

Ambient fabrication is an economically advantageous strategy to reduce the manufacturing costs of perovskite solar cells (PSCs). The conventional antisolvent solvent extraction approach complicates the ambient fabrication of perovskites by requiring precise deposition and careful selection of antisolvents. Additionally, most ambient fabrication efforts have focused on methylammonium lead iodide perovskite and yielded small grain sizes, which limit the performance and stability of PSCs. In this study, we address these challenges by incorporating a urea additive in a gas-quenching approach to fabricate high-quality cesium-formamidinium lead halide (CsFA) PSCs under 40% relative humidity (RH) conditions. A combination of Fourier transform infrared spectroscopy (FTIR) measurement and density functional theory (DFT) calculation shows that the urea additive induces the formation of a urea-perovskite adduct complex, which extends the annealing window of the perovskite from 1.8 to 5.3 min and leads to compact perovskite films with grain sizes exceeding 1 μm. These ambient-fabricated CsFA perovskite films with the inclusion of the urea additive exhibit superior stability under accelerated mixed-stress conditions (85 °C/40%RH and 85 °C/40%RH/0.7 sun + UV illumination). The application of the urea-modified perovskite absorber in a completed device based on the conventional Spiro-OMeTAD/Ag structure resulted in improved performance, achieving efficiencies of up to 16.2% with a fill factor (FF) exceeding 80%. Moreover, the integration of the urea-based perovskite film into an all-ambient PSC, utilizing a CuSCN/carbon architecture, yields a champion performance of 13.3%. Furthermore, the all-ambient PSCs incorporating the urea additive exhibited long-term stability, maintaining approximately 80% of their initial efficiency after 2400 h of storage under 30%RH conditions.