Absence of presumed ferroelectricity in methylammonium lead chloride single crystals representing organic-inorganic hybrid perovskites

Abstract

The performance of organic-inorganic metal halide perovskites as photovoltaics has been exceptional over the last decade, which is attributed to their unique properties like high absorption coefficient, tunable band gap, high conversion efficiency and a lot more. It is believed that the presence of ferroelectricity in the system assists charge separation leading to an increase in their efficiency. Many researchers have also claimed them to be ferroelectrics. However, there is debate among the researchers about their structures at different temperatures which questions their polar or non-polar nature and hence the presence of ferroelectricity in them. In the present study, this controversy over ferroelectric behavior of hybrid perovskites has been addressed, on MAPbCl3 single crystals. Through temperature dependent x-ray diffraction, Raman spectroscopy, dielectric permittivity, P-E (Polarization versus electric field) and PUND (Positive up negative down) measurements, it has been shown that the organic inorganic metal halide sample, MAPbCl3, is not ferroelectric and the structure is non-polar in the entire studied temperature range. These results will help in resolving the controversy present in the existing literature regarding the ferroelectric nature of organic inorganic metal halide perovskites MAPbX3 with X as Cl, Br or I.