The existence of a mass oxidation of Sn 2+ that takes place mainly during preparation of precursor solutions and fabrication of films creates a lead-free solar cell of low open-circuit voltage, which leads to low PCE. To reduce the oxidation process, we employed an innovative crystal fabrication method with anti-solventfree recrystallization technology. As a result, to the best of our knowledge, both spin-coated and printed lead-free solar cells based on FASnI 3 achieved the highest 3D-based PCE to date.

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