Unraveling the water degradation mechanism of CH${}_3$NH${}_3$PbI${}_3$

Abstract

Instability of perovskite photovoltaics is still a topic which is currently under intense debate, especially the role of water environment. Unraveling the mechanism of this instability is urgent to enable practical application of perovskite solar cells. Here, ab initio metadynamics is employed to investigate the initial phase of a dissolution process of CH${}_3$NH${}_3$PbI${}_3$ (MAPbI${}_3$) in explicit water. It is found that the initial dissolution of MAPbI${}_3$ is a complex multi-step process triggered by the departure of I${}^{-}$ ion from the CH${}_3$NH${}_3$I-terminated surface. Reconstruction of the free energy landscape indicates a low energy barrier for water dissolution of MAPbI${}_3$. In addition, we propose a two-step thermodynamic cycle for MAPbI${}_3$ dissolution in water at a finite concentration that renders a spontaneity of the dissolution process. The low energy barrier for the initial dissolution step and the spontaneous nature of MAPbI${}_3$ dissolution in water explain why the water immediately destroys pristine MAPbI${}_3$. The dissolution thermodynamics of all-inorganic CsPbI${}_3$ perovskite is also analyzed for comparison. Hydration enthalpies and entropies of aqueous ions play an important role for the dissolution process. Our findings provide a comprehensive understanding to the current debate on water instability of MAPbI${}_3$.

arXiv comment32 pages, 5 figures

References in corpus (10)

• Escaping free-energy minima
• Atomistic origins of high-performance in hybrid halide perovskite solar cells
• PLUMED: a portable plugin for free-energy calculations with molecular dynamics
• Band structure diagram paths based on crystallography
• Intrinsic Instability of the Hybrid Halide Perovskite Semiconductor CH3NH3PbI3
• Ionization energy as a stability criterion for halide perovskites
• Methylammonium fragmentation in amines as source of localized trap levels and the healing role of Cl in Hybrid Lead-Iodide Perovskites
• Aziridinium lead iodide: a stable, low bandgap hybrid halide perovskite for photovoltaics
• Structural dynamics in hybrid halide perovskites: Bulk Rashba splitting, spin texture, and carrier localization
• Degradation by Exposure of Co-Evaporated CH3NH3PbI3 Thin Films

Cited by in corpus (3)

• Optical Memory, Switching, and Neuromorphic Functionality in Metal Halide Perovskite Materials and Devices
• Atomistic insights into the degradation of halide perovskites: a reactive force field molecular dynamics study
• Influence of interstitial Li on the electronic properties of Li${}_x$CsPbI${}_3$ for photovoltaic and battery applications