Phase Transition and Band Gap Regulation by Halogen Substituents on the Organic Cation in Organic–Inorganic Hybrid Perovskite Semiconductors

In the last decade, hybrid materials have received widespread attention. In particular, hybrid lead halide perovskite-type semiconductors are very attractive owing to their great flexibility in band gap engineering. Here, by using precise molecular modifications, three one-dimensional perovskite-type semiconductor materials are designed and obtained: [Me₃PCH₂X][PbBr₃] (X=H, F, and Cl for compounds 1 , 2 , and 3 , respectively). The introduction of a heavier halogen atom (F or Cl) to [Me₄P]⁺ increases the potential energy barrier required for the tumbling motion of the cation, hence achieving the transformation of the phase transition temperature from low temperature (192 K) to room temperature (285 K) and high temperature (402.3 K). Moreover, the optical band gaps reveal a broadening trend with 3.176 eV, 3.215 eV, and 3.376 eV along the H→F→Cl series, which is attributed to the formation of the structural distortion.