• SHIVANI GROVER

      Articles written in Bulletin of Materials Science

    • Effect of humidity on the orientational ordering of CH$_3$NH$_3^+$ in methylammonium lead iodide

      SHIVANI GROVER UMESH V WAGHMARE

      More Details Abstract Fulltext PDF

      With high energy conversion efficiency and low-cost production, hybrid organic–inorganic perovskite solar cells (PSCs) have the potential to be alternative to silicon-based technology. However, there are concerns about their longterm stability and environmental friendliness, which must necessarily be addressed to enable large-scale commercialization of PSCs. Here, we use first-principles theory to determine and understand the effects of humidity on theT-dependent tetragonal to cubic structural transition in CH$_3$NH$_3$PbI$_3$, which can impact the long-term stability of its properties. We show that ferroelectric vs. antiferroelectric structural ordering in CH$_3$NH$_3$PbI$_3$ is influenced by humidity. Within first-principles density functional theory, we determine the lowest energy configurations of dipolar ordering in CH$_3$NH$_3$PbI$_3$$\cdot$$x$H$_2$O and effects of their interaction with H$_2$O molecules. Developing a simple effective Hamiltonian tomodel these configurations, we use Monte Carlo simulations to determine temperature-dependent structural phase transitions in CH$_3$NH$_3$PbI$_3$. We establish ferroelectric ordering in MAPbI$_3$ at low temperature, and demonstrate that it changes to antiferroelectric ordering of MA$^+$ cations at $x>0.2$ in CH$_3$NH$_3$PbI$_3$$\cdot$$x$H$_2$O.

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