Design the π-stacking type of perovskite-like iodobismuthates to enhance their optoelectronic properties

One-dimension (1D) or two-dimension (2D) iodobismuthates are promising perovskite-like photoactive materials for electronic devices. Many researchers focused on how to qualitatively build frameworks to increase the dimension of charge transformation due to the construction of connectivity between bismuth halide ions as the key to achieve ideal properties. In this context, two kinds of organic amine compounds, benzylamine and N-methylaniline, were well-designed and corresponding iodobismuthates single crystals: BA3Bi2I9 and NMA3Bi2I9 (BA = C6H5CH2NH3+, NMA = C6H5(CH3)NH2+) were prepared by solvent evaporation process. Their crystals characterized by S-XRD, SEM, etc. After thoroughly investigated their structures, optical and electronic properties, the results show that the space group changed from C2/c (BABI) to P21/c (NMABI) due to the π-stacking type shifted from I-type to Z-type. So as to the reconstruction of their band structures and the C 2p of BABI is more closed to the band edge than that of NMABI revealed by density functional theory (DFT). Although BABI has higher electrical resistivity, higher trap-state density and lower carrier mobility, its optoelectronic property is superior to NMABI as a result of the I-type π-stacking increased the electronic dimensionality.