[(CH3 )3 NH]3 Bi2 I9 : A Polar Lead-Free Hybrid Perovskite-Like Material as a Potential Semiconducting Absorber.

Perovskite hybrids of lead organometal halides, most notably CH3 NH3 PbI3 , have shown extremely promising applications in the field of optoelectronics, because of their remarkable semiconducting and light-absorbing properties. However, two key issues-the toxicity of lead and the poor ambient instabilities-have restrained their further commercialization. Herein, we have designed a new stable polar lead-free hybrid material by utilizing the strategy of cation substitution, [(CH3 )3 N]3 Bi2 I9 (1), which adopts the 0D inorganic perovskite-like architecture by face-sharing BiI6 octahedra. It is interesting that 1 displays excellent absorbing properties with a narrow optical band gap of ≈2.0 eV, and positive temperature-dependent conductivity confirms its semiconducting behaviors. In addition, 1 has good phase stability against decomposition under ambient conditions, much superior to that of CH3 NH3 PbI3 . This work suggests the potential of 1 as a lead-free semiconducting absorber with high phase stability for photoelectric applications.