Room temperature ferroelectricity and blue photoluminescence in zero dimensional organic lead iodine perovskites

Abstract

Organic–inorganic hybrid perovskite materials have attracted great attention due to their great application potential in photovoltaics and optoelectronics. Among them, some 2D and 1D lead-iodide-based perovskites were found to exhibit ferroelectricity at room temperature. Yet, no 0D lead-iodide-based perovskites were reported to be room temperature ferroelectric. Here, we report a new lead-iodide-based perovskite material, (DMA)₄PbI₆, which is ferroelectric at room temperature. The spontaneous polarization of (DMA)₄PbI₆ is about 0.3 μC cm⁻². (DMA)₄PbI₆ undergoes a ferroelectric–ferroelectric phase transition around 252 K in the heating process. The ferroelectric–ferroelectric phase transition is a first order phase transition with a hysteresis of 18 K between the heating process and the cooling process. The absorption spectra show that (DMA)₄PbI₆ is a direct band material with a band gap of 2.80 eV. A broadband blue photoluminescence centered at 2.7 eV was observed, which may be attributed to the self-trapped excitons.