Recently, lead‐free double perovskites have emerged as a promising environmentally friendly photovoltaic material for their intrinsic thermodynamic stability, appropriate bandgaps, small carrier effective masses, and low exciton binding energies. However, currently solar cell based on these double perovskites has been reported, due to the challenge in film processing. For lead‐free perovskite solar cells (PSCs), tin is at the focus owing to a similar diameter and valence to lead, which prompts people to substitute lead with tin to form ASnX₃ perovskite films. However, the highest PCE of tin‐based device achieved was only 6.4%, which is lower than lead‐based perovskite solar cell. More importantly, Sn²⁺ ion in the material is unstable and easily to be oxidized to Sn⁴⁺, leading to a destruction of photovoltaic performance. It is still difficult to develop new lead‐free perovskites with good intrinsic stability for photovoltaic applications.