The conventional precursor mixture based on highly pure and expensive PbI₂ (purity >99.99%) is problematic in commercializing perovskite solar cells (PSCs) because of a large deviation in the batch-to-batch photovoltaic performance due to underlying nonstoichiometry and/or the nonperovskite phase. Here, we report on reproducibly efficient (>21%) PSCs based on the ambient-temperature-stable δ-phase FAPbI₃ powder, synthesized by reacting PbI₂ (either homemade or low-grade commercial product with purity <99%) with formamidinium iodide (FAI) at room temperature (∼93% yield). X-ray diffraction patterns confirm that annealing the spin-coated film leads to phase purity of cubic α FAPbI₃. As compared to the conventional precursor mixture based on PbI₂ (purity = 99.9985%), significantly reducing defects in the powder-based film is responsible for the stable and reproducible efficiency. In addition, the homogeneous light-intensity-dependent surface photocurrent contributes to the reproducibility of photovoltaic performance. The quasi-steady-state power conversion efficiency of 21.07% is certified for the device based on FAPbI₃ powder.

中文翻译：

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预先合成的FAPbI ₃粉末可实现可再生且高效（> 21％）的钙钛矿太阳能电池

基于高纯度和昂贵的PbI ₂（纯度> 99.99％）的常规前驱物混合物在钙钛矿型太阳能电池（PSC）的商业化中存在问题，因为由于潜在的非化学计量和/或化学性质，批次之间的光伏性能存在较大差异。非钙钛矿相。在此，我们报告了基于环境温度稳定的δ相FAPbI ₃粉末的可再生有效（> 21％）PSC，该粉末是通过使PbI ₂（纯度低于99％的自制或低档商业产品）与甲ami反应而合成的室温下碘化物（FAI）（约93％的收率）。X射线衍射图证实，对旋涂膜进行退火可导致立方晶αFAPbI _3的相纯度。与传统的基于PbI _2的前体混合物（纯度= 99.9985％）相比，粉末状薄膜中缺陷的明显减少是稳定和可重复生产的效率的原因。另外，依赖于光强度的均匀表面光电流有助于光伏性能的可再现性。基于FAPbI ₃粉末的器件的准稳态功率转换效率为21.07％。