SnOx as Bottom Hole Extraction Layer and Top In Situ Protection Layer Yields over 14% Efficiency in Sn-Based Perovskite Solar Cells

Sn-based perovskite solar cells (S-PSCs) are a promising candidate to replace toxic Pb-based PSCs. For promoting their industrial application, developing inorganic substitutions of unstable poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is also an important part due to its intrinsic stability and low cost. Here, we in situ prepared ambipolar SnOx by a simple and fast plasma-assistant strategy (P-SnOx). The as-prepared P-SnOx works as a hole transport layer directly, yielding a 10.89 ± 0.51% power conversion efficiency (PCE) comparable to a PEDOT:PSS-based device (10.39 ± 0.72%). The top SnOx (T-SnOx), composed of SnO2 and Sn metal, as a modifier and a protection layer of the perovskite by reducing Sn4+ to Sn2+, gives a 13.08 ± 0.33% device performance. This in situ top protective strategy combined with P-SnOx as a hole transport layer further boosts the champion PCE of S-PSCs to 14.09% (13.5 ± 0.32%).