MRS Meetings and Events


EN05.10.27 2023 MRS Fall Meeting

Interstitial Defect Thermodynamics Drive Phase Separation in Lead Halide Perovskites

When and Where

Nov 29, 2023
8:00pm - 10:00pm

Hynes, Level 1, Hall A



Ross Kerner1,John Lyons2,Kai Zhu1,Joseph Berry1,3

National Renewable Energy Laboratory1,U.S. Naval Research Laboratory2,University of Colorado Boulder3


Ross Kerner1,John Lyons2,Kai Zhu1,Joseph Berry1,3

National Renewable Energy Laboratory1,U.S. Naval Research Laboratory2,University of Colorado Boulder3
Lead halide perovskites show unrivaled performance and versatility in optoelectronic devices; however, the issues of photo- and electrochemical stability and halide phase segregation remain a challenge to take full advantage of halide perovskites. Here, we describe our proposed model to explain how homogeneously mixed iodide (I):bromide (Br) perovskite alloys (e.g. MAPbBr<sub>x</sub>I<sub>1-x</sub>) phase separate into I-rich and Br-rich regions under bias or illumination. The model predicts iodine +1 interstitials play a critical, intrinsic role giving rise to unequal fluxes of halide species – the origin of voltage- or photo-induced compositional instabilities. We briefly review our recent experimental results testing the model and discuss in detail our recent density functional theory (DFT) computations comparing the relative formation enthalpies of I<sub>i</sub><sup>+</sup> versus Br<sub>i</sub><sup>+</sup> interstitial defects in different halide compositions. We find that I<sub>i</sub><sup>+</sup> defects are energetically favorable by 0.1-0.4 eV over Br<sub>i</sub><sup>+</sup> under most conditions, and also show that I<sub>i</sub><sup>+</sup> is further stabilized when surrounded by iodide first- and second-nearest neighbors. In other words, I<sub>i</sub><sup>+</sup> will be most stable and favorably migrate towards iodide-rich regions making them more iodide-rich. Thus, we confirm our model’s core assumption and elucidate a major fundamental, thermodynamic driving force for halide phase separation following oxidation and creation of I<sub>i</sub><sup>+</sup> defects. Overall, this body of work brings a level of clarity to interstitial defect chemistry and physics in halide perovskites, advancing our understanding a step closer to that of more conventional semiconductors.


defects | perovskites | thermodynamics

Symposium Organizers

Marina Leite, University of California, Davis
Lina Quan, Virginia Institute of Technology
Samuel Stranks, University of Cambridge
Ni Zhao, Chinese University of Hong Kong

Symposium Support

Enli Technology Co., LTD

APL Energy | AIP Publishing

Session Chairs

So Min Park
Lina Quan

In this Session

Interstitial Defect Relaxation DFT Study of Lead Halide Perovskites

Water-Assisted Morphology and Crystal Engineering of Hybrid Organic-Inorganic Halide Perovskite: Implications for Optoelectronic Properties

Self-Leveling Inks for Engineering Large Area Uniformity in High-Performance Flexography-Printed Perovskite Solar Cells

Towards Highly Efficient Fully Evaporated Perovskite/Si Tandem Solar Cells

The Outstanding Role of Dielectricity in Hybrid Solar Cell Absorbers

Controlling The Crystallization of Pure Bromide Quasi-2-Dimensional Perovskite Crystals for High Efficiency Pure-Blue Light-Emitting Diodes

Compositional Engineering of Single-Crystal Perovskite for Highly Efficient Photovoltaics

Atomistic Origin of Transparent Absorption Spectra of Halide Perovskites

Exploring a Novel Family of Conjugated Polymers for High Efficiency and Thermally Stable Perovskite Solar Cells

Charge Transfer Doping of Ruddlesden–Popper Metal–Halide Perovskites via Bulk Incorporation of Organic Molecular Dopants

View More »

Publishing Alliance

MRS publishes with Springer Nature