Synthesis, structure and optical properties of (H2DMAPA)BiBr5, (H2DMAPA)BiBr2I3, (H2DMAPA)2AgBiBr8 and (H2EP)2AgBiBr8 lead-free perovskites

The toxicity of lead limits the commercial application of lead-based perovskites . Replacing lead with an environment-friendly metal is an excellent alternative strategy. Bi 3+ is an interesting choice being that it has satisfactory biological security and similar electron configuration to Pb 2+ . Series of hybrid Bi 3+ perovskites, (H 2 DMAPA)BiBr 5 ( 1 ), (H 2 DMAPA)BiBr 2 I 3 ( 2 ), (H 2 DMAPA) 2 AgBiBr 8 ( 3 ) and (H 2 EP) 2 AgBiBr 8 ( 4 ) were successfully prepared in this work. Their band gaps are 2.65, 2.21, 2.58 and 2.33 ​eV, respectively. The excitation wavelengths of 1 , 2 , 3 and 4 are 440, 355, 365 and 400 ​nm, and the corresponding PL emission peaks are located at 480, 580, 493 and 467 ​nm, respectively.