Efficient lead (Pb)-free inverted planar formamidinium tin triiodide (FASnI(3)) perovskite solar cells (PVSCs) are demonstrated. Our FASnI(3) PVSCs achieved average power conversion effi ciencies (PCEs) of 5.41% +/- 0.46% and a maximum PCE of 6.22% under forward voltage scan. The PVSCs exhibit small photocurrent-voltage hysteresis and high reproducibility. The champion cell shows a steady-state effi ciency of approximate to 6.00% for over 100 s.