Jonghee Yang

Yonsei University

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Mahshid Ahmadi

University of Tennessee at Knoxville

Whikun Yi

Karlsruhe Institute of Technology

Sergei V. Kalinin

University of Tennessee at Knoxville

Hyosung Choi

Hanyang University

Junyoung Lee

Ulsan National Institute of Science and Technology

Jongtaek Lee

Soongsil University

Hochan Song

Hanyang University

Bo Ram Lee

Sungkyunkwan University

Benjamin J. Lawrie

Oak Ridge National Laboratory

Yongtao Liu

Oak Ridge National Laboratory

Cooperative Institutions

Hanyang University

Government of the Republic of Korea

Anyang University

Sungkyunkwan University

Ulsan National Institute of Science and Technology

University of Tennessee at Knoxville

Oak Ridge National Laboratory

Samsung (South Korea)

Chinese Academy of Sciences

National Renewable Energy Laboratory

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Field emission enhancement of PbS colloidal quantum dot-decorated single-walled carbon nanotubes

Journal of Alloys and Compounds (2019)

Jonghee Yang Junyoung Lee Whikun Yi

Lead sulfide

10.1016/j.jallcom.2019.151832

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Citations (6)

High-Throughput Automated Exploration of Phase Growth Kinetics in Quasi-2D Formamidinium Metal Halide Perovskites

Jonghee Yang Benjamin J. Lawrie Sergei V. Kalinin Mahshid Ahmadi

Quasi-two-dimensional (2D) metal halide perovskites (MHPs) are an emerging material platform for sustainable functional optoelectronics, however the uncontrollable, broad phase distribution remains a critical challenge for applications. This is because the basic principles for controlling multiple phases in quasi-2D MHPs remain poorly understood, due to the rapid crystallization kinetics during the conventional thin-film fabrication process. Herein, a high-throughput automated synthesis-characterization-analysis workflow is implemented to accelerate material exploration in formamidinium (FA)-based quasi-2D MHP compositional space, revealing the early-stage phase growth kinetics which fundamentally determines the phase distributions. We observe that the prominent n=2 2D phase restricts the growth kinetics of 3D-like phases – α-FAPbI3 MHPs where the spacers are coordinated to the surface. δ-FAPbI3 phase further inhibits the growth of 3D-like phases. It is found that thermal annealing is a critical step for proper phase growth, although it can lead to the emergence of unwanted local PbI2 crystallites. Additionally, fundamental insights into the precursor chemistry associated with spacer-solvent interaction that determines the morphologies and microstructures of quasi-2D MHP films are demonstrated. Our high-throughput study provides comprehensive insights into the fundamental principles in quasi-2D MHP phase control and enables new control of the functionalities of complex materials systems for sustainable device applications.

Formamidinium

Characterization

10.26434/chemrxiv-2023-zcvl0

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Citations (3)

Quantum Dot-in-Mechanoluminescent Matrix for Full-Color Implementation

SSRN Electronic Journal (2022)

Hong In Jeong Jonghee Yang Woo Hyeon Jeong Jae Taek Oh Hochan Song

Mechanoluminescence (ML), a novel process that converts mechanical momentum to light emission, has shown potential for sustainable future technologies. However, the lights emitted from classical ML materials have shown broad emission spectra and the limitation in the choice of colors so far, constraining the full-color implementation of ML. Herein, a quantum dot (QD)-in-mechanoluminescent matrix (QMM) architecture is introduced by simply incorporating QDs with the classical ML-active matrices, designed to utilize the sharp emission spectra of the QDs. The QMMs demonstrate distinctive green and red lights identical to the emissions from the QDs through mechanical stimuli, achieving the purest ML reported to date. Furthermore, the deployments of the QDs allow the full-color implementation of ML covering a wide color gamut, as well as the demonstration of the purest white reported to date. Systematic investigations reveal that the ML operation in the QMM is governed according to the ML-stimulated PL mechanism, preventing energy or charge transfer processes. Moreover, the QMMs exhibit excellent stabilities upon environmental stresses and the patterned system is readily prepared, guaranteeing both robustness and easy processability of the system. This simple QMM strategy suggests practical insights for the development of powerless ML display and lighting systems.

Matrix (chemical analysis)

Full color

10.2139/ssrn.4103215

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Citations (2)

Accelerating Materials Discovery by High‐Throughput GIWAXS Characterization of Quasi‐2D Formamidinium Metal Halide Perovskites

Advanced Functional Materials (2024)

Jonghee Yang Juanita Hidalgo Donghoon Song Sergei V. Kalinin Juan‐Pablo Correa‐Baena

Abstract The intriguing functionalities of emerging quasi‐2D metal halide perovskites (MHPs) have led to further exploration of this material class for sustainable and scalable optoelectronic applications. However, the chemical complexities in precursors—primarily determined by the 2D:3D compositional ratio—result in uncontrolled phase heterogeneities in these materials, which compromises the optoelectronic performances. Yet, this phenomenon remains poorly understood due to the massive quasi‐2D compositional space. To systematically explore the fundamental principles, herein, a high‐throughput automated synthesis‐characterization workflow is designed and implemented to formamidinium (FA)‐based quasi‐2D MHP system. It is revealed that the stable 3D‐like phases, where the α‐FAPbI 3 surface is passivated by 2D spacers, exclusively emerge at the compositional range (35–55% of FAPbI 3 ), deviating from the stoichiometric considerations. A quantitative crystallographic study via high‐throughput grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) experiments integrated with automated peak analysis function quickly reveals that the 3D‐like phases are vertically aligned, facilitating vertical charge conduction that can be beneficial for optoelectronic applications. Together, this study uncovers the optimal 2D:3D compositional range for complex quasi‐2D MHP systems, realizing promising optoelectronic functionalities. The automated experimental workflow significantly accelerates materials discoveries and processing optimizations that are transferrable to other deposition methods, while providing fundamental insights into complex materials systems.

Formamidinium

Characterization

10.1002/adfm.202409293

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The Role of SnO₂ Processing on Ionic Distribution in Double-Cation–Double Halide Perovskites

ACS Applied Materials & Interfaces (2023)

Holland Hysmith So Yeon Park Jonghee Yang Anton V. Ievlev Yongtao Liu

Moving toward a future of efficient, accessible, and less carbon-reliant energy devices has been at the forefront of energy research innovations for the past 30 years. Metal-halide perovskite (MHP) thin films have gained significant attention due to their flexibility of device applications and tunable capabilities for improving power conversion efficiency. Serving as a gateway to optimize device performance, consideration must be given to chemical synthesis processing techniques. Therefore, how does common substrate processing techniques influence the behavior of MHP phenomena such as ion migration and strain? Here, we demonstrate how a hybrid approach of chemical bath deposition (CBD) and nanoparticle SnO2 substrate processing significantly improves the performance of (FAPbI3)0.97(MAPbBr3)0.03 by reducing micro-strain in the SnO2 lattice, allowing distribution of K+ from K-Cl treatment of substrates to passivate defects formed at the interface and produce higher current in light and dark environments. X-ray diffraction reveals differences in lattice strain behavior with respect to SnO2 substrate processing methods. Through use of conductive atomic force microscopy (c-AFM), conductivity is measured spatially with MHP morphology, showing higher generation of current in both light and dark conditions for films with hybrid processing. Additionally, time-of-flight secondary ionization mass spectrometry (ToF-SIMS) observed the distribution of K+ at the perovskite/SnO2 interface, indicating K+ passivation of defects to improve the power conversion efficiency (PCE) and device stability. We show how understanding the role of ion distribution at the SnO2 and perovskite interface can help reduce the creating of defects and promote a more efficient MHP device.

Passivation

10.1021/acsami.3c03520

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Understanding the cation-selective ligand passivation for AgBiS2 nanocrystal photovoltaics

Chemical Engineering Journal (2023)

Sung Yong Bae Jonghee Yang Jae Taek Oh Cheong Beom Lee Hochan Song

Passivation

10.1016/j.cej.2023.145674

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Citations (15)

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

The Journal of Physical Chemistry Letters (2023)

Yongtao Liu Jonghee Yang Rama K. Vasudevan Kyle P. Kelley Maxim Ziatdinov

Electronic transport and hysteresis in metal halide perovskites (MHPs) are key to the applications in photovoltaics, light emitting devices, and light and chemical sensors. These phenomena are strongly affected by the materials microstructure including grain boundaries, ferroic domain walls, and secondary phase inclusions. Here, we demonstrate an active machine learning framework for "driving" an automated scanning probe microscope (SPM) to discover the microstructures responsible for specific aspects of transport behavior in MHPs. In our setup, the microscope can discover the microstructural elements that maximize the onset of conduction, hysteresis, or any other characteristic that can be derived from a set of current-voltage spectra. This approach opens new opportunities for exploring the origins of materials functionality in complex materials by SPM and can be integrated with other characterization techniques either before (prior knowledge) or after (identification of locations of interest for detail studies) functional probing.

Hysteresis

Scanning Probe Microscopy

Characterization

10.1021/acs.jpclett.3c00223

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Citations (21)

[The influence of ambient air pollution on reproductive health: current situation and prospects].

PubMed (2017)

Yinchun Zhang Jonghee Yang Lu Ma

10.3760/cma.j.issn.0253-9624.2017.03.001

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Citations (2)

Supramolecular design principles in pseudohalides for high-performance perovskite solar mini modules

Joule (2024)

Hochan Song Hak-Beom Kim Seong Chan Cho Jeongjae Lee Jonghee Yang

Passivation

Perovskite solar cell

10.1016/j.joule.2024.05.019

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Citations (6)

Understanding the Ligand-Assisted Reprecipitation of CsPbBr3 Perovskite Nanocrystals via High Throughput Robotic Synthesis Approach

Sheryl L. Sanchez Jonghee Yang Mahshid Ahmadi

Inorganic cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNCs) have rendered promising performances in various optoelectronic applications. In contrast to the complex hot-injection synthesis, the ligand-assisted reprecipitation (LARP) method renders a simple route enabling mass-production of high-quality PNCs. However, LARP synthesis is susceptible, and thus, little has been deeply understood about how to control the growth of PNCs and the optical characteristics of the PNCs. Herein, by implementing a high-throughput automated experimental platform, we explore the growth behaviors and colloidal stability of the LARP-synthesized PNCs. Using two distinctive acid-base pairs - oleic acid-oleylamine and octanoic acid-octylamine, we systematically explore the influence of ligands - chain lengths, concentration and ratios - on the particle growths and consequent functionalities of the PNCs. We observe that the short-chain ligands cannot make functional PNCs with desired sizes and shapes, whereas the long-chain ligands provide homogeneous and stable PNCs. The PNCs transform into a Cs-rich non-perovskite structure with poorer emission functionalities and larger size distributions by employing excessive amines or polar antisolvent. This proposes that the diffusion of the ligands in a reaction system crucially determines the structures and functionalities of the PNCs. Our high-throughput exploration provides a detailed guidance on synthesis routes for desired PNCs.

Oleylamine

10.26434/chemrxiv-2023-bgcg0

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Citations (6)