A Room-Temperature Hybrid Lead Iodide Perovskite Ferroelectric

Abstract

Organic-inorganic hybrid perovskite, [CHNH]PbI, holds a great potential for next-generation solar devices. However, whether the ferroelectricity exists in [CHNH]PbI and results in the ultrahigh performance is not at present clear. Beyond that, no hybrid lead iodide perovskite ferroelectric has yet been found. Here, using precise molecular modifications, we successfully designed a room-temperature hybrid perovskite ferroelectric, [(CH)NCHI]PbI. Because of the high-symmetry and nearly spherical shape of [(CH)N] cation, [(CH)N]PbI crystallizes in a centrosymmetric space group P6/ m at room temperature and undergoes a structural phase transition at 184 K. Accompanied by the introduction of halogen atoms on the cation from F to I, the phase transition temperature gradually increases to 312 K and the space group transforms into a polar C2 at room temperature. The strongest halogen bond energy of [(CH)NCHI]-I and the largest volume of [(CH)NCHI] among these compounds might be possible reasons for the stabilization of ordered [(CH)NCHI] cation array and further reservation of its ferroelectricity at relatively high temperature. This work provides an efficient molecular design strategy toward the targeted harvest of room-temperature organic-inorganic perovskite ferroelectrics, and should inspire further exploration of the interplay between structure and ferroelectricity. The discovery of lead iodide perovskite ferroelectric also offers a foothold to the possibility for the existence of ferroelectricity in [CHNH]PbI.

H/F‐Substitution‐Induced Homochirality for Designing High‐Tc Molecular Perovskite Ferroelectrics

“…We noted that a mono‐fluorinated molecule is geometrically very similar to its parent molecule, since the substitution of H by an F atom is one of the commonly employed monovalent isosteric replacements . In this way, the fluorinated compounds tend to have similar crystal structures to the hydrogen analogs, and maintain the possibility of orientational disorder as well as phase transitions . And meanwhile, it is through this incorporation of the most electronegative species that not only the barrier of rotation but also the strength of dipole moment of the organic molecules get raised, pointing out an obvious route to enhance the T c and P s .…”

A Nickel(II) Nitrite Based Molecular Perovskite Ferroelectric

“…But unfortunately, the halogen substituted OHPs ([(CH 3 ) 3 NCH 2 X][Ni(NO 2 ) 3 ], X=F, Cl, Br, I) crystallize in the centrosymmetric space groups (Supporting Information, Table S1). Considering that halogen bonding and hydrogen bonding have a substantial role in generating ferroelectric ordering, [(CH 3 ) 4 N] + was substituted with a hydroxy group so as to act as hydrogen‐bond donors when nitrite groups are the acceptors. However, the resulting OHPs with the orthorhombic centrosymmetric space group Pnma persist the non‐ferroelectric feature (Supporting Information, Table S1).…”

Spintronics of Hybrid Organic–Inorganic Perovskites: Miraculous Basis of Integrated Optoelectronic Devices

“…In optical absorption and emission capability tests, TMCM‐MnCl 3 showed six absorption peaks in its spectrum that correspond to the electronic transitions between the ground and the excited states of the Mn 2 + ion, and the wavelength of the emitted light is ≈640 nm . Molecules of TMBM‐MnBr 3 , TMCM‐CdBr 3 and TMIM‐PbI 3 also have similar structures to TMCM‐MnCl 3 and have phase transition temperatures of 415, 346, and 312 K, respectively . Another 1D HOP ferroelectric was synthesized in 2015 by Liao et al They reported a hybrid organo‐plumbate, (benzylammonium) 2 PbCl 4 , which behaves like a semiconductor material.…”