Nontoxic bismuth-based hybrid inorganic-organic double perovskites with high air stability

In recent years, lead-containing perovskite solar cells have attracted great attention in the photovoltaic field, but the toxicity of lead has seriously affected its commercial application. Developing lead-free perovskite materials is challenging. In this paper, the properties of GA(2)CuBiI(6) (GA = C(NH2)(3)(+)) and GA(2)KBiI(6) are simulated by the first principle, and the results show that the valence band maximum (VBM) of GA(2)CuBiI(6) or GA(2)KBiI(6) mainly comes from the contribution of the d orbit of Cu or thep orbital of K, and their conduction band minimum (CBM) mainly comes from the contribution of the p orbit of I. GA(2)Cu(x)K(1-x)BiI(4-x)Cl(2+x) (x=0.10-0.30) double perovskite materials are synthesized by wet chemistry method. The resulted double perovskite materials have an indirect band gap of about 2.00 eV, and Cu+ doping ratio has some influence on their band gap. At Cu+ doping ratio of 0.20, the least crystalline defects and the highest conductivity of the double perovskites are obtained. The structure and morphology of GA(2)Cu(0.2)K(0.8)BiI(3.8)Cl(2.2) double perovskite thin films remain high stability within 20 d. These results show that GA(2)Cu(x)K(1-x)BiI(4-x)Cl(2+x) double perovskite materials are potentially an environmentally friendly alternative to the lead-containing perovskite semiconductors.