Science News: 2021 Angew. Chem. Int. Ed., Nearly 21% PCE, High-quality and Stable α-FAPbI₃ Perovskite

　　Angewandte Chemie (IF 15.336) journal recently published the research results of Michael Grätzel from Institute of Chemical Sciences and Engineering, Switzerland. The research team successfully fabricated a pure phase and stable α-FAPbI₃ perovskite film without MA through a combination strategy of precursor engineering and grain anchoring.

　　Excellent photoelectric performance and high thermal stability make α-FAPbI₃ (α-Formamidinium lead iodide) one of the most promising materials for perovskite solar cells. However, it is quite challenging to make α-FAPbI₃ with pure composition, phase purity and stability. In this study, the research team used FA-based volatile additives to design a precursor solution to completely inhibit the formation of non-perovskite δ-FAPbI₃ during the film crystallization process. They penetrated 4-tert-butyl-benzylammonium iodide into α-FAPbI₃ to fix and stabilize the crystal grains of the α phase.

　　The research team used a solar simulator to analyze the photovoltaic characteristics of perovskite solar cells and used quantum efficiency measurement system to perform EQE (External Quantum Efficiency) spectral analysis. At the same time, the short-circuit current of the solar cell under the solar simulator was compared with Jsc (short-circuit current density) to prove the authenticity of the experiment. Research results showed that the efficiency of FAPbI₃ perovskite solar cells has reached to nearly 21%, which is one of the current highest values. In addition, the FAPbI₃ perovskite solar cell exhibited high thermal stability. After storing for more than 1600 hours at 50°C, it still maintained about 90% of its initial efficiency. This research opened new way for the manufacture of high-quality perovskite thin films and optoelectronic devices.