Mixed cation perovskite solid state solar cell and fabrication thereof

A perovskite material including an organic-inorganic perovskite structure of formula (I), AnMX3 (I), n being the number of cation A and an integer >4, A being a monovalent cation selected from inorganic cations Ai and/or from organic cations Ao, M being a divalent metal cation or a combination thereof, X being a halide and/or pseudohalide anion or a combination thereof, wherein at least one cation A is selected from organic cations Ao, the inorganic cations Ai are independently selected from Li+, Na+, K+, Rb30, Cs+, or Tl+ and the organic cations Ao are independently selected from ammonium (NH4+), methyl ammonium (MA) (CH3NH3+), ethyl ammonium (CH3CH2NH3)+, formamidinium (FA) (CH(NH2)2+), methylformamidinium (CH3C(NH2)2+), guanidium (C((NH)2)3+), tetramethylammonium ((CH3)4N+), dimethylammonium ((CH3)2NH230) or trimethylammonium ((CH3)3NH+).