Interfacial Chemical Bridge Constructed by Zwitterionic Sulfamic Acid for Efficient and Stable Perovskite Solar Cells

A simple-structure zwitterion of sulfamic acid (⁺H₃N–SO₃^–, SA) is introduced to construct an effective chemical bridge between SnO₂ and a perovskite layer through a coordination bond via the -SO₃^– anion for remedying the oxygen vacancies of SnO₂ and meanwhile to passivate charged defects of the perovskite through electrostatic interaction via the -NH₃⁺ cation. The introduced SA results in high-quality perovskite films with large grain size, due to the better wettability for perovskite solution. Consequently, the SA-modified solar cell generates an enhanced efficiency from 18.2% to 20.4% with negligible hysteresis. Remarkably, the unsealed device with SA modification also exhibits considerably improved stability.