Self-Assembled Organic Cations-Assisted Band-Edge Tailoring In Bismuth-Based Perovskites For Enhanced Visible Light Absorption And Photoconductivity

Bismuth-based zero-dimensional perovskites garner high research interest because of their advantages, such as excellent moisture stability and lower toxicity in comparison to lead-based congeners. However, the wide optical bandgap (>2 eV) and poor photoconductivity of these materials are the bottlenecks for their optoelectronic applications. Herein, we report a combined experimental and theoretical study of the structural features and optoelectronic properties of two novel and stable zero-dimensional bismuth perovskites: (biphenyl bis(methylammonium)) 1.5BiI6 center dot 2H(2)O (BPBI) and (naphthalene diimide bis-(ethylammonium)) 1.5BiI6 center dot 2H(2)O (NDBI). NDBI features a remarkably narrower bandgap (1.82 eV) than BPBI (2.06 eV) because of the significant orbital contribution of self-assembled naphthalene diimide cations at the band edges of NDBI. Further, the FP-TRMC analysis revealed that the photoconductivity of NDBI is about 3.7-fold greater than that of BPBI. DFT calculations showed that the enhanced photoconductivity in NDBI arises from its type-lla band alignment, whereas type-Ib alignment was seen in BPBI.