Exploring the Relationship of Microstructure and Conductivity in Metal Halide Perovskites via Active Learning-Driven Automated Scanning Probe Microscopy

Article Chemistry, Physical

Understanding the Role of Cesium on Chemical Complexity in Methylammonium-Free Metal Halide Perovskites

Jonghee Yang et al.

Summary: Mixed cesium- and formamidinium-based metal halide perovskites (MHPs) are promising photovoltaic materials, but high cesium ratios result in chemical complexities and local inhomogeneities, compromising the optoelectronic performance.

ADVANCED ENERGY MATERIALS (2023)

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Article Chemistry, Physical

Learning the right channel in multimodal imaging: automated experiment in piezoresponse force microscopy

Yongtao Liu et al.

Summary: We developed automated experiment workflows for identifying the best predictive channel in spectroscopic measurements. The approach combines ensembled deep kernel learning for probabilistic predictions and reinforcement learning for channel selection. The implementation in multimodal imaging of piezoresponse force microscopy (PFM) showed that the amplitude is the best predictive channel for polarization-voltage and frequency-voltage hysteresis loop areas. This workflow and code can be applied to other multimodal imaging and local characterization methods.

NPJ COMPUTATIONAL MATERIALS (2023)

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Article Nanoscience & Nanotechnology

Disentangling ferroelectric domain wall geometries and pathways in dynamic piezoresponse force microscopy via unsupervised machine learning

Sergei Kalinin et al.

Summary: In this study, domain switching pathways in ferroelectric materials were explored using a variational autoencoder, allowing for the visualization of domain evolution mechanisms and their correlation with the microstructure.

NANOTECHNOLOGY (2022)

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Article Nanoscience & Nanotechnology

Nanoscale chemical heterogeneity dominates the optoelectronic response of alloyed perovskite solar cells

Kyle Frohna et al.

Summary: By combining quantitative optical spectroscopic techniques and synchrotron nanoprobe measurements, we can visualize the nanoscale chemical, structural, and optoelectronic landscape in halide perovskite devices. Compositional disorder plays a dominant role in the optoelectronic response, while the influence of nanoscale strain variations is weaker.

NATURE NANOTECHNOLOGY (2022)

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Article Multidisciplinary Sciences

Local nanoscale phase impurities are degradation sites in halide perovskites

Stuart Macpherson et al.

Summary: Understanding the nanoscopic chemical and structural changes is crucial for mitigating device degradation in emerging energy materials. Researchers have developed a multimodal microscopy toolkit to investigate the impact of phase impurities on the performance and longevity of formamidinium-rich perovskite absorbers. The study also demonstrates that manipulating these impurities can alleviate performance losses and intrinsic degradation processes.

NATURE (2022)

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Article Multidisciplinary Sciences

Initializing film homogeneity to retard phase segregation for stable perovskite solar cells

Yang Bai et al.

Summary: The mixtures of cations and anions in hybrid halide perovskites for solar cells often undergo segregation, limiting device lifetime. By adding selenophene, the distribution of ions in the film becomes more homogeneous, resulting in improved efficiency and prolonged operational lifetime.

SCIENCE (2022)

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Article Multidisciplinary Sciences

Mapping structure heterogeneities and visualizing moisture degradation of perovskite films with nano-focus WAXS

Nian Li et al.

Summary: In this study, nano-focused wide-angle X-ray scattering was used to map the heterogeneities of perovskite films. The results show that the top film region bears tensile strain and perovskite grains deposited by sequential spray-coating grow along the vertical direction. Moreover, moisture degradation primarily occurs at the perovskite-air interface and grain boundaries, and the tensile strain on the top surface has a profound influence on the moisture degradation.

NATURE COMMUNICATIONS (2022)

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Editorial Material Chemistry, Physical

Nanoscopic impurities trigger perovskite degradation

Mingwei Hao et al.

Summary: The role of nanoscopic impurities in perovskite solar cells, which induce degradation through active ion-photocarrier coupling, has been elucidated using multimodal characterizations.

JOULE (2022)

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Article Chemistry, Multidisciplinary

Automated Experiments of Local Non-Linear Behavior in Ferroelectric Materials

Yongtao Liu et al.

Summary: An automated experiment is developed to investigate structural, chemical, and functional behaviors in complex materials and uncover the primary physical mechanisms that control device function. By exploring non-linear electromechanical responses in piezoresponse force microscopy (PFM), it is discovered that different materials exhibit different non-linear behavior patterns, and automated experiments have the potential to distinguish between competing physical mechanisms.

SMALL (2022)

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Article Chemistry, Multidisciplinary

Exploring Physics of Ferroelectric Domain Walls in Real Time: Deep Learning Enabled Scanning Probe Microscopy

Yongtao Liu et al.

Summary: The functionality of ferroelastic domain walls in ferroelectric materials is explored using computer vision algorithms in real-time scanning probe microscopy experiments. A robust deep convolutional neural network (DCNN) is implemented for real-time operations and analysis of data streams, and the dynamic ferroelastic domain walls in different thin films are observed through experiments. This work establishes a framework for real-time data analysis and discusses strategies to mitigate the effects of out-of-distribution.

ADVANCED SCIENCE (2022)

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Review Energy & Fuels

Advances and challenges in understanding the microscopic structure-property-performance relationship in perovskite solar cells

Yuanyuan Zhou et al.

Summary: The emergence of perovskite photovoltaic technology has greatly advanced our understanding of metal halide perovskite thin-film microstructures and their effects on optoelectronic properties, device efficiency, and stability. This article discusses the morphological characteristics of three key microstructure types in perovskites, explores their impacts on performance and degradation, and calls for more research on hidden microstructures and high-spatiotemporal-resolution characterizations.

NATURE ENERGY (2022)

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Article Computer Science, Artificial Intelligence

AtomAI framework for deep learning analysis of image and spectroscopy data in electron and scanning probe microscopy

Maxim Ziatdinov et al.

Summary: AtomAI is an open-source software package that bridges instrument-specific Python libraries, deep learning, and simulation tools into a single ecosystem, aiming to establish a connection between microscopy observations and materials behaviour.

NATURE MACHINE INTELLIGENCE (2022)

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Article Computer Science, Artificial Intelligence

Experimental discovery of structure-property relationships in ferroelectric materials via active learning

Yongtao Liu et al.

Summary: This article reports on the development and implementation of a machine learning framework that actively discovers relationships between local domain structure and polarization-switching characteristics in ferroelectric materials. The framework utilizes hysteresis loops and their scalar descriptors to guide the discovery of these relationships via automated piezoresponse force microscopy and spectroscopy experiments. The results demonstrate that the discovery path and sampling points of on- and off-field hysteresis loops are largely different, indicating that they are dominated by different mechanisms. The proposed approach is applicable to a broad range of modern imaging and spectroscopy methods.

NATURE MACHINE INTELLIGENCE (2022)

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Article Chemistry, Multidisciplinary

Direct Observation of Photoinduced Ion Migration in Lead Halide Perovskites

Yongtao Liu et al.

Summary: The study directly observes photoinduced ion migration in HOIPs, demonstrating that light illumination induces significant CH3NH3+ migration but not I-/Br- migration. Light effects on the migration of organic cation and halides in HOIPs are revealed to be distinct, offering insights for improving the performance and stability of HOIPs optoelectronics.

ADVANCED FUNCTIONAL MATERIALS (2021)

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Article Physics, Applied

Probing polarization dynamics at specific domain configurations: Computer-vision based automated experiment in piezoresponse force microscopy

Kyle P. Kelley et al.

Summary: By implementing an automated experimentation approach, functional properties in ferroelectric thin films can be explored by visualizing ferroelectric domain structures, using a computer vision-based algorithm to discover features of interest, and employing dimensionality reduction techniques to reveal characteristic polarization behaviors.

APPLIED PHYSICS LETTERS (2021)

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Article Chemistry, Multidisciplinary

Correlating Crystallographic Orientation and Ferroic Properties of Twin Domains in Metal Halide Perovskites

Yongtao Liu et al.

Summary: Metal halide perovskite (MHP) solar cells have gained global attention in research. Understanding the crystal orientation and ferroic properties of MHP twin stripes is essential to comprehend the impact of ferroic behavior on the optoelectronic properties. Investigating these aspects provides insight into the influence of subgrain structures in MHPs.

ACS NANO (2021)

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Article Chemistry, Multidisciplinary

Role of Decomposition Product Ions in Hysteretic Behavior of Metal Halide Perovskite

Yongtao Liu et al.

Summary: Ion migration plays a crucial role in metal halide perovskite semiconductor devices, but the mechanisms and effects are not fully understood. Direct observation reveals that decomposition products of CH3NH3+ accumulate at interfaces under light and bias conditions, impacting device performance and stability, highlighting the need for consideration in future optimization studies.

ACS NANO (2021)

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Article Chemistry, Physical

Unraveling the hysteretic behavior at double cations-double halides perovskite-electrode interfaces

Dohyung Kim et al.

Summary: This study investigates the hysteretic behavior in (FAPbI(3))(0.85)(MAPbBr(3))(0.15) perovskite devices and reveals pronounced charge dynamics hysteresis in the off-field. Under illumination, transient and hysteretic behaviors are significantly reduced, with the hysteretic behavior strongly associated with the accumulation of Br- ions at the interfaces.

NANO ENERGY (2021)

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Article Chemistry, Multidisciplinary

Disentangling Ferroelectric Wall Dynamics and Identification of Pinning Mechanisms via Deep Learning

Yongtao Liu et al.

Summary: This study explored domain dynamics in model polycrystalline materials using deep learning and rVAE methods. The research found that these methods can be used to unambiguously identify and classify ferroelectric and ferroelastic domain walls, providing insights into the intrinsic mechanisms of polarization switching.

ADVANCED MATERIALS (2021)

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Article Materials Science, Multidisciplinary

Multimodal microscopy characterization of halide perovskite semiconductors: Revealing a new world (dis)order

Samuel D. Stranks

Summary: Halide perovskites exhibit heterogeneity in their properties on different length scales, with grain, sub-grain, and atomic scales being the most important yet least understood. Efforts to understand these relationships through multimodal and correlative microscopy have led to key conclusions to enhance performance and stability. Future adaptations will utilize machine-learning algorithms to process large datasets and operando measurements for refining processing and device architectures.

MATTER (2021)

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Article Chemistry, Multidisciplinary

Identifying high-performance and durable methylammonium-free lead halide perovskites via high-throughput synthesis and characterization

Yu An et al.

Summary: This study investigates the crystallographic and optical properties of mixed cation and mixed halide lead perovskites, revealing a correlation between tolerance factor and structure but also showing that tolerance factor alone cannot predict complete perovskite formation. Among 26 different compositions, Cs(1/6)FA(5/6)PbI(3) demonstrates the highest efficiency and long-term stability in iodide-rich compositions, highlighting the importance of understanding structure-property relationships in designing durable perovskite materials.

ENERGY & ENVIRONMENTAL SCIENCE (2021)

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Article Computer Science, Artificial Intelligence

Decoding the shift-invariant data: applications for band-excitation scanning probe microscopy *

Yongtao Liu et al.

Summary: The shift-VAE is an unsupervised method for analyzing spectral data in the presence of shifts along the parameter axis, with applications in various fields such as band-excitation piezoresponse force microscopy data analysis, denoising of data, and model-free dimensionality reduction in imaging and spectroscopic data.

MACHINE LEARNING-SCIENCE AND TECHNOLOGY (2021)

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Article Chemistry, Multidisciplinary

Two birds with one stone: dual grain-boundary and interface passivation enables >22% efficient inverted methylammonium-free perovskite solar cells

Saba Gharibzadeh et al.

Summary: This study successfully enhanced the efficiency and stability of inverted p-i-n structured perovskite solar cells using a dual passivation strategy, achieving high power conversion efficiency and good stability.

ENERGY & ENVIRONMENTAL SCIENCE (2021)

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Review Chemistry, Physical