SEU published the latest research results in Advanced Materials

Recently, with the funding of “SEU Top 10 Scientific and Technological Issues”, on the basis of “Ferroelectrochemistry” discipline established by the research team from Jiangsu Provincial Key Laboratory of “Molecular Ferroelectric Science and Application”, School of Chemistry and Chemical Engineering, SEU, the team managed to synthesize the first lead-free 3D hybrid perovskite ferroelectric semiconductor (CH3PH3) SnBr3 based on methylphosphonium (Fig. 1) by fully utilizing the theoretical basis and research inferences in Ferroelectrochemistry. This is the first breakthrough in terms of 3D hybrid perovskite materials after methylamine and formamidine. Both the P element and the N element are listed in the VA group of the periodic table of elements and feature similar bond properties. However, as the element P is in the third period, the methylphosphonium cation features a larger volume and heavier mass, which can not only meet the needs of constructing the 3D stannous bromide perovskite ferroelectric materials, but also increase the rotational energy barrier, thus increasing the phase transition temperature obviously. It is worth noting that this work represents another typical case of successfully designing molecular ferroelectrics based on the momentum matching theory in the discipline of Ferroelectrochemistry, and also provides a promising new A-site cation for the construction of 3D hybrid perovskite ferroelectric semiconductors. Related results were published online with the title of “Methylphosphonium Tin Bromide: A 3D Perovskite Molecular Ferroelectric Semiconductor” in Advanced Materials, the top international journal in the field of material. The 3D organic-inorganic hybrid lead halide perovskite material represented by (CH3NH3)PbI3 has attracted wide attentions for its functional diversity and broad development prospects in the field of photoelectric application (with the photoelectric conversion efficiency as high as 25.5%). The excellent photovoltaic performance of the well-known 3D (CH3NH3)PbI3 is believed to benefit from its ferroelectric polarization. In recent years, although scientists have made great efforts in expanding the family of 3D hybrid perovskites, very little result has been achieved because A-site is only limited to methylamine or formamidine cations.

It is reported that the team, as inspired by the work results, has also developed other methylphosphine-based hybrid perovskite materials such as (CH3PH3)SnI3. Among them, (CH3PH3)SnI3 also showed more outstanding ferroelectric and semiconductor properties (1.43 eV, Fig. 2), while its methylamine/formamidine analogs failed to achieve the ferroelectricity at room temperature. The methylphosphine-based solar cell devices as prepared on such basis have exhibited excellent photoelectric properties (currently, the photoelectric conversion efficiency is 2.2% without additives), which is the third type of 3D ferroelectric perovskite solar cells in the world independently developed by Chinese researchers. This case also verified that the ferroelectrochemistry would certainly play a breakthrough role in many fields such as chemical catalysis, material design and device application in the future.

Zhang Hanyue, a doctoral student from School of Chemistry and Chemical Engineering, is the first author and corresponding author of this paper, and Southeast University is the only corresponding and completion institute.

(Correspondent: Xiong Ren’gen)

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