Degradable Additive Couple Enable Pure and Stable Alpha-Phase FAPbI<sub>3</sub> for Perovskite Solar Cells.

Lin, Xuesong; Su, Hongzhen; Shen, Xiangqian; Qin, Zhenzhen; Chen, Mengjiong; Zhang, Ziyang; Zheng, Guanhaojie; Wang, Yanbo et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Pure black-phase FAPbI<sub>3</sub> has always been pursued because of its ideal bandgap (E<sub>g</sub>) and high thermal stability. Here, a pair of sacrificial agents containing diethylamine hydrochloride (DEACl) and formamide (Fo) is reported, which can induce the oriented growth of black-phase FAPbI<sub>3</sub> along (111) and will disappear by the aminolysis reaction during perovskite annealing, retaining the E<sub>g</sub> of FAPbI<sub>3</sub> as 1.49 eV. In addition, the tensile strain of the target FAPbI<sub>3</sub> is found to be mitigated with a stabilized black phase due to the tilt of FA<sup>+</sup>. The devices based on the pure and stable black-phase (111)-FAPbI<sub>3</sub> achieved a power conversion efficiency of 25.2% and 24.2% (certified 23.51%) with an aperture area of 0.09 and 1.04 cm<sup>2</sup>, respectively. After 1080 h of operation at the maximum power point under 1-sun illumination (100 mW cm<sup>-2</sup>), the devices maintained 91.68 ± 0.72% of the initial efficiencies.