(C 7 H 18 N 2 )PbI 4 : A 2D Hybrid Perovskite Solid-State Phase Transition Material with Semiconducting Properties.

Two-dimensional organic-inorganic hybrid perovskites (OIHPs) have gained attention as a result of their flexibility and adjustability of the structure. However, the large band gap of two-dimensional perovskites limits their application in the photoelectric field. In the present work, we report a two-dimensional organic-inorganic hybrid compound of (C ₇ H ₁₈ N ₂ )PbI ₄ ( 1 ) with a narrow band gap, which consists of [PbI ₄ ] ^2- _n layers and N -(2-aminoethyl)piperidinium cations. 1 exhibits semiconducting properties with a narrow optical band gap of ∼2.02 eV and a photoelectric response with a ratio of photocurrent to dark current of ∼100. In addition, it exhibits a reversible solid-state phase transition at 228 K. This finding should inspire research into more 2D layered OIHPs with the combination of phase transition and semiconductor properties.