The Competition Between Mechanical Stability and Charge Carrier Mobility in MA-based Hybrid Perovskites: Insight from DFT

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Bristowe, PD 
Lee, Jung-Hoon 
Bristowe, Nicholas C 
Cheetham, Anthony K 

Hybrid organic-inorganic perovskites and their inorganic analogues, such as MAPbI3 (MA = methylammonium, CH3NH3) and CsPbI3, are currently under intense investigation due to their high-power conversion efficiencies and low cost for solar cell applications. Herein, we investigate the effect of methylammonium and the inorganic A-cations on the elastic and related transport properties of halide perovskites using van der Waals (vdW) corrected density functional theory (DFT) calculations. For inorganic halide perovskites we find that the bonding within the inorganic framework is mainly responsible for their elastic behavior. However, our DFT calculations show that when a MA cation is substituted into the structure the combined effects of stericity (conformation) and hydrogen-framework interactions improve the material’s resistance to deformation. For example, the orientationally-averaged Young’s modulus of orthorhombic MAPbI3 increases by about 19 % compared to the equivalent inorganic series of structures. We also find that, within the carrier-acoustic phonon scattering regime, the electron and hole carrier mobilities of hybrid halide perovskites are lowered by the hydrogen-bonding-induced tilting of the inorganic octahedra. Taken together, these results can help guide the optimization of the mechanical and transport properties of perovskite-based solar cell materials.

3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences, 3406 Physical Chemistry
Journal Title
Journal of Materials Chemistry C
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Journal ISSN
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Royal Society of Chemistry (RSC)
Engineering and Physical Sciences Research Council (EP/P022596/1)
The studies were supported by the Winton Programme for the Physics of Sustainability (J-HL), the Cambridge Overseas Trust (ZD), the China Scholarship Council (ZD) and the Ras Al Khaimah Center for Advanced Materials (AKC). NCB was supported by the Royal Commission for the Exhibition of 1851, and an Imperial College Research Fellowship. The calculations were performed at the UK National Supercomputing Service, Journal of Materials Chemistry C Page 20 of 27 Journal of Materials Chemistry C Accepted Manuscript Published on 08 October 2018. Downloaded by University of Cambridge on 10/10/2018 6:43:02 PM. View Article Online DOI: 10.1039/C8TC04750B 21 ARCHER. Access to the latter was obtained via the UKCP consortium and funded by EPSRC under Grant No. EP/P022596/1.