First-principles identification of the charge-shifting mechanism and ferroelectricity in hybrid halide perovskites

Bumseop Kim,Jeongwoo Kim,Noejung Park

doi:10.1038/s41598-020-76742-7

Abstract

Hybrid halide perovskite solar cells have recently attracted substantial attention, mainly because of their high power conversion efficiency. Among diverse variants, (CH3NH3)PbI3 and HC(NH2)2PbI3 are particularly promising candidates because their bandgap well matches the energy range of visible light. Here, we demonstrate that the large nonlinear photocurrent in β-(CH3NH3)PbI3 and α-HC(NH2)2PbI3 is mostly determined by the intrinsic electronic band properties near the Fermi level, rooted in the inorganic backbone, whereas the ferroelectric polarization of the hybrid halide perovskite is largely dominated by the ionic contribution of the molecular cation. The spatial charge shift upon excitation is attributed to the charge transfer from iodine to lead atoms in the backbone, which is independent of the presence of the cationic molecules. Our findings can serve as a guiding principle for the design of future materials for halide-perovskite solar cells with further enhanced photovoltaic performance.

Highlights

Hybrid halide perovskite solar cells have recently attracted substantial attention, mainly because of their high power conversion efficiency
At low temperatures (< 130 K), whereas M APbI3 exhibits an orthorhombic gamma (γ) phase consisting of rotated octahedra (Fig. 1e), the beta phase becomes stable for F APbI3. β-MAPbI3 has been explored as a promising candidate for harvesting solar energy[9]; the low photoactivity of δ-FAPbI3 has hampered its utilization for the photovoltaic effect
As a result of extensive density functional theory (DFT) calculations, we find that, the ferroelectric polarization sharply depends on the alignment of the molecular cations, the large shift current is mainly determined by the intrinsic band structure of the Pb–I backbone

Summary

Introduction

Hybrid halide perovskite solar cells have recently attracted substantial attention, mainly because of their high power conversion efficiency. Among various materials for PSCs, the halide perovskites, C H3NH3PbI3 (methylammonium lead iodide, MAPbI3) and HC(NH2)2PbI3 (formamidinium lead iodide, FAPbI3), are the most promising candidates in terms of optical absorption and carrier mobility[1,4]. A comparison and contrast of electronic properties between MAPbI3 and FAPbI3, which are the most promising candidates among the known halide perovskites, may concretize the search direction for materials that enhance the light-harvesting efficiency PSCs

Methods

Results

Conclusion