With great achievements in efficiency,stability,and large-scale preparation of perovskite solar cells (PSCs),the com-mercialization of PSC is ongoing,but there is still an issue on lead toxicity.Although lead content in the device is low,the water solubility of lead salts leads to potential environmental pollution.At present,the non-lead perovskites studied in-clude:divalent metal perovskite (e.g.,Sn2+,Ge2+,Cu2+),trivalent metal perovskite (e.g.,Bi3+,Sb3+,In3+),tetravalent met-al double perovskite (e.g.,Sn4+,Pd4+,Ti4+,Pt4+) and mono-trivalent mixed double perovskite (e.g.,Ag+ and Bi3+,Ag+ and In3+,Ag+ and Sb3+).Their properties are summarized in Table 1.Since the first report on non-lead double perovskite Cs2AgBiBr6 in 2016[1],this material has caused extensive re-search in optoelectronic devices because of its long carrier lifetime[1] and good stability[2].However,owing to its wide and indirect bandgap (Eg) (～2.0 eV),its light absorption range is narrow,which limits its application in photovoltaics.At present,the power conversion efficiency (PCE) of Cs2AgBiBr6 device is ～3％[3].To enhance PCE,the Eg needs to be nar-rowed.The efforts in this area focus on adjusting chemical composition and physical structure (Fig.1) to tune Eg.