Multifunctional potassium thiocyanate interlayer for eco-friendly tin perovskite indoor and outdoor photovoltaics

[Display omitted] •KSCN was introduced as multifunctional layer in tin perovskite photovoltaics.•KSCN functioned as suppressed antioxidation and perovskite crystallization.•The target device presented an outdoor efficiency of 11.17% under AM 1.5G.•The target device delivered an indoor efficiency of 17.57% under 1062 lx. Serious issues such as easy-oxidation of Sn2+, fast crystallization rate and high defect density are still existing in tin perovskites to restrain their photovoltaic performance. Herein, a strategy of bottom passivation by potassium thiocyanate (KSCN) has been developed in FA0.75MA0.25SnBrI2-based perovskite solar cells. KSCN interlayer exhibited multifunctional roles in aligning energy levels, assisting perovskite crystallization and promoting charge transport. The resulting champion device delivered superior power conversion efficiency (PCE) as high as 11.17% under AM 1.5G illumination. It is worth noting that the champion indoor photovoltaics efficiency under 2956 K@1062 lx (334.41 μW/cm2) illumination could approach 17.57%, which is the highest PCE for tin perovskite photovoltaics to our knowledge. The outstanding indoor performance demonstrates the huge application potential of eco-friendly tin perovskites.