First-principles study of the quasi-one-dimensional organic-inorganic hybrid perovskites ( MV ) A I 3 Cl 2 ( MV = methylviologen ; A = Bi , Sb )

Many ferroelectric (FE) organic-inorganic hybrid perovskites (OIHPs) show great promise in the fields of photovoltaic cells and information memory devices. We systematically investigated the FE, optical, and electric properties of quasi-one-dimensional OIHPs $(\mathrm{MV})A{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ ($\mathrm{MV}=\mathrm{methylviologen}, A=\mathrm{Bi},\mathrm{Sb}$) using density functional theory calculations. The FE polarization mechanism of $(\mathrm{MV})A{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ mainly originates from octahedral distortion along the direction of octahedral chains with the $p\text{\ensuremath{-}}p$ coupling of ${A}^{3+}$ cations and ${\mathrm{I}}^{\ensuremath{-}}$ anions. Due to the loosely coupled FE chains, $(\mathrm{MV})\mathrm{Bi}{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ and $(\mathrm{MV})\mathrm{Sb}{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ possess a relatively low energy barrier of polarization switching at the 180\ifmmode^\circ\else\textdegree\fi{} reversal of the FE polarization. The estimated upper limit memory densities of 14.9 and $15.0\phantom{\rule{0.16em}{0ex}}\mathrm{Tb}/\mathrm{c}{\mathrm{m}}^{2}$ for $(\mathrm{MV})\mathrm{Bi}{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ and $(\mathrm{MV})\mathrm{Sb}{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$, respectively, hold promise to be applied to high-density FE memory devices. The strong anisotropic optical absorption of $(\mathrm{MV})A{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ is in the visible light region, and its estimated maximum power conversion efficiencies are g23%. The high anisotropic carrier mobility in $(\mathrm{MV})A{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ enhances the separation of electron-hole pairs. Both $(\mathrm{MV})\mathrm{Bi}{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ and $(\mathrm{MV})\mathrm{Sb}{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$ possess positive piezoelectric effect; therefore, strain design is an effective approach to enhance power conversion efficiency and carrier mobility of $(\mathrm{MV})A{\mathrm{I}}_{3}{\mathrm{Cl}}_{2}$, leading to experimental design of FE photovoltaic cell.