Tetragonal CH3NH3PbI3 Is Ferroelectric

Abstract

Halide perovskite (HaP) semiconductors are revolutionizing photovoltaic (PV) solar energy conversion by showing remarkable performance of solar cells made with esp. tetragonal methylammonium lead tri-iodide (MAPbI3). In particular, the low voltage loss of these cells implies a remarkably low recombination rate of photogenerated carriers. It was suggested that low recombination can be due to spatial separation of electrons and holes, a possibility if MAPbI3 is a semiconducting ferroelectric, which, however, requires clear experimental evidence. As a first step we show that, in operando, MAPbI3 (unlike MAPbBr3) is pyroelectric, which implies it can be ferroelectric. The next step, proving it is (not) ferroelectric, is challenging, because of the material s relatively high electrical conductance (a consequence of an optical band gap suitable for PV conversion!) and low stability under high applied bias voltage. This excludes normal measurements of a ferroelectric hysteresis loop to prove ferroelctricity s hallmark for switchable polarization. By adopting an approach suitable for electrically leaky materials as MAPbI3, we show here ferroelectric hysteresis from well-characterized single crystals at low temperature (still within the tetragonal phase, which is the room temperature stable phase). Using chemical etching, we also image polar domains, the structural fingerprint for ferroelectricity, periodically stacked along the polar axis of the crystal, which, as predicted by theory, scale with the overall crystal size. We also succeeded in detecting clear second-harmonic generation, direct evidence for the material s non-centrosymmetry. We note that the material s ferroelectric nature, can, but not obviously need to be important in a PV cell, operating around room temperature.

Abstract (p:1), Main text [Includes 7 figures] (P:2-13), References (p:14-17), Supporting information (p:18-36)

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Cited by in corpus (22)

• Perovskites for Solar and Thermal Energy Harvesting: State of the Art Technologies, Current Scenario and Future Directions
• The tetragonal phase of CH${}_3$NH${}_3$PbI${}_3$ is strongly anharmonic
• Static Rashba Effect by Surface Reconstruction and Photon Recycling in the Dynamic Indirect Gap of APbBr3 (A = Cs, CH3NH3) Single Crystals
• Enhanced Piezoelectric Response in Hybrid Lead Halide Perovskite Thin Films via Interfacing with Ferroelectric PbZr${}_{0.2}$Ti${}_{0.8}$O${}_3$
• Polar or nonpolar? That is not the question for perovskite solar cells
• Coherent Band-Edge Oscillations and Dynamic LO Phonon Mode Splitting as Evidence for Polaronic Coupling in Perovskites
• First principles study of ferroelastic twins in halide perovskites
• Cesium-involved electron transfer and electron-electron interaction in high-pressure metallic CsPbI3
• Competition between Polar and Antiferrodistortive Modes and Correlated Dynamics of the Methylammonium Molecules in MAPbI${}_3$ from Anelastic and Dielectric Measurements
• "Forbidden" polarisation and extraordinary piezoelectric effect in organometallic lead halide perovskites
• Pressure and Inversion Symmetry Breaking Field Driven First Order Phase Transition and Formation of Dirac Circle in Perovskites
• From latent ferroelectricity to hyperferroelectricity in alkali lead halide perovskites
• Defining the Topological Influencers and Predictive Principles to Engineer Band Structure of Halide Perovskites
• Spin Texture as Polarization Fingerprint of Halide Perovskites
• Polarization Origin of Photoconductivity in MAPbI3 Thin Films
• Domain boundaries in Luttinger-Tisza ordered dipole lattices
• Radiative recombination of large polarons in halide perovskites
• Between Structure and Performance in Halide Perovskites for Photovoltaic Applications: the Role of Defects
• Observation of Analogue Dynamic Schwinger Effect and Non-Perturbative Light Sensing in Lead Halide Perovskites
• Dielectric softening in the halide double perovskites $A_2$Au${}_2{X}_6$ ($A$: Cs, Rb; $X$: Cl, Br, I) via a strain-mediated pseudotriggered mechanism
• Effect of Orientation of Cation CH3NH3PbI3 on Ambipolarity, Open-Circuit Voltage, and Excitons Lifetime
• Iodide-methylammonium interaction is responsible for ferroelectricity in CH3NH3PbI3