Accelerated Formation of CsPbI 3 through Controlled Amidation of Intermediate Phases
Yitian Du, Vladimir V. Shilovskikh, Anatol Prudnikau, Ran Ji, Noel Israel, Zongbao Zhang, Shivam Singh, Alexander Thomas, Kashimul Hossain, Chunqiu Zheng, Fabian Paulus, Boris Rivkin, Yana VaynzofABSTRACT
The all‐inorganic metal halide perovskite CsPbI 3 is a promising photovoltaic absorber owing to its thermal stability and suitable bandgap for tandem applications. The most common approach to depositing CsPbI 3 from solution is based on the use of dimethylammonium iodide (DMAI); however, removing DMAI during crystallization is challenging, as it introduces residues that can lead to higher defect densities and trigger degradation. Here, we introduce a reaction‐guided crystallization strategy based on 2,2,2‐trifluoroethyl trifluoroacetate (TFTF), which undergoes a rapid ester‐amine amidation reaction with DMAI during annealing. By converting DMAI into highly volatile products, the TFTF reaction drives a smooth, additive residue‐free transition to γ‐CsPbI 3 and produces pinhole‐free films with low defect densities. Devices fabricated using this strategy deliver an open‐circuit voltage (V OC ) of 1.20 V and a champion efficiency of 20.8%, along with markedly improved operational stability. This intermediate‐management approach provides a practical, chemically defined pathway for directing CsPbI 3 crystallization and advancing high‐performance inorganic iodide perovskite photovoltaics.