Regulated Lattice Structure of Quasi-2D/3D Tin-Perovskite Absorbers by Fluorinated Phenethylammonium Cation for Stabilized Lead-Free Perovskite Solar Cells

Lead-free perovskite solar cell is a promising next-generation eco-friendly photovoltaic technology. Particularly, much effort has been devoted in tin-based perovskite solar cells due to idealtical outer electric and ionic radius configuration of Sn²⁺ to Pb²⁺ cation. However, there remains a detrimental oxidation issue of Sn²⁺ to Sn⁴⁺ causing accelerated self-doping within the interface or grain boundaries of the perovskite absorber layer in ambient conditions. In this work, a fluorinated phenethylammonium iodide (4FPEA) was introduced in a typical quasi-2D/3D tin-perovskite absorber layer to enforce strong hydrogen bonding in the octahedral lattice, which can effectively passivate the defective antisites and retain enhanced oxidation resistance of the perovskite absorber layer. As a result, 4FPEA could contribute to enhancing the oxidation stability of tin-perovskite absorbers and resulting perovskite solar cells. The optimized 4FPEA-based tin-perovskite solar cells achieve promising photovoltaic performance of >4% PCE as the trap state density within defective grain boundaries were successfully passivated. Moreover, the optimized concentration of 4FPEA demonstrated antioxidation properties that were being worked over 1,000 hours under the atmospheric condition of 25 °C and RH 17%.