Lead-sulfur interaction induced damp and water stability in pure formamidinium lead triiodide

Summary

Research efforts in various multitudes have been demonstrated to stabilize methylammonium (MA)- and bromide (Br)-free formamidinium lead triiodide (FAPI) perovskite thin films. Despite these commendable efforts, pure FAPI perovskite thin film is prone to critical phase-transition issues due to its thermodynamically stable non-perovskite phase (2H). Here, in this work, we propose a rational additivization strategy to overcome this challenge. Our multifunctional ammonium salt containing a sulfur heteroatom shifts the thermodynamic stability from the 2H phase to an intermediate phase closer to the cubic phase. Along with the high crystallinity, micron-sized grains with preferred (00h) facet orientation stem the Pb ^…S interaction to offer exceptional stability against high relative humidity, direct water incursion, and shelf-life aging. Our findings through experimental and theoretical studies substantiate the role of Pb ^…S interaction in stabilizing the perovskite cubic phase and the stoichiometric distribution of elemental components.

Graphical abstract

Highlights

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  Pb ^…S interaction to stabilize FAPbI ₃

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  FAPbI ₃ stabilized in water immersion

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  The thermodynamic stability of FAPbI ₃ shifted from the 2H phase

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  Uncovering the mechanistic insights for multifunctional additivization approach

Abstract

Haris et al. implement a multifunctional additivization strategy where the sulfur heteroatom induced strong interactions; this prevents water and damp invasion to the formamidinium lead triiodide perovskite layer. The strategy also demonstrates the shifting of thermodynamic stability of FAPbI ₃ from an unfavorable 2H phase to a favorable intermediate phase.