Ammonium Thiocyanate Enhanced High-Performance Quasi-Two-Dimensional Perovskite Solar Cells

The quality of the tin oxide (SnO2)/perovskite interface has become eminently critical for high-efficiency and stable quasi-two-dimensional (Q2D) perovskite solar cells (PSCs). Based on this, we propose the application of a multifunctional passivator, ammonium thiocyanate (NH4SCN), to treat the SnO2/perovskite interface of Q2D PSCs. It can passivate oxygen vacancies effectively by the interaction of the highly electronegative thiocyanate with uncoordinated Sn, thereby reducing interfacial defects and regulating energy levels. In addition, the use of NH4SCN improves the wettability of perovskite precursors on tin oxide films, thus enhancing the quality of perovskite films. The strategy of NH4SCN interfacial passivation shows better energy level matching and consequently a higher photoelectric conversion efficiency (PCE) compared to the conventional method as an additive. The improved devices achieved a maximum PCE of 21.96%, an impressive stability of sustaining 90% of the initial PCE after 3000 h in the ambient condition.