ORCID Profile
0000-0002-1586-1466
Current Organisation
Argonne National Laboratory
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Publisher: Wiley
Date: 21-06-2021
Abstract: Hybrid organic–inorganic perovskites are one of the promising candidates for the next‐generation semiconductors due to their superlative optoelectronic properties. However, one of the limiting factors for potential applications is their chemical and structural instability in different environments. Herein, the stability of (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 perovskite solar cell is explored in different atmospheres using impedance spectroscopy. An equivalent circuit model and distribution of relaxation times (DRTs) are used to effectively analyze impedance spectra. DRT is further analyzed via machine learning workflow based on the non‐negative matrix factorization of reconstructed relaxation time spectra. This exploration provides the interplay of charge transport dynamics and recombination processes under environment stimuli and illumination. The results reveal that in the dark, oxygen atmosphere induces an increased hole concentration with less ionic character while ionic motion is dominant under ambient air. Under 1 Sun illumination, the environment‐dependent impedance responses show a more striking effect compared with dark conditions. In this case, the increased transport resistance observed under oxygen atmosphere in equivalent circuit analysis arises due to interruption of photogenerated hole carriers. The results not only shed light on elucidating transport mechanisms of perovskite solar cells in different environments but also offer an effective interpretation of impedance responses.
Publisher: AIP Publishing
Date: 06-2023
DOI: 10.1063/5.0146892
Abstract: In photovoltaic module manufacturing processes, it is essential to achieve high production reliability of modules based on the given cells with scattered characteristics. This study aims to investigate the optimal cell sorting method to minimize the deviation of module power via simulation analysis. We consider the given solar cells to have different electrical characteristics with Gaussian distributions and ideal interconnections. We examine the resultant power distributions of modules for various cell sorting methods based on multiple cell parameters such as maximum power current, maximum power voltage, and maximum power of the cells. Our simulation shows that the average power maximum of the modules in different sorting methods has a marginal difference, and the mismatch loss by different cell characteristics is not a key factor to reduce the module reliability, but the standard deviation of the maximum powers of modules can be largely reduced by one order of magnitude if the cells are sorted out based on the reference of the average power maximum of the participated cells. Our study will provide useful guidance for cost-efficient and reliable photovoltaic modules in the manufacturing process.
Publisher: American Chemical Society (ACS)
Date: 28-05-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1TA10944H
Abstract: This study reveals that light–ferroelectricity interaction in 2D (4,4-DFPD) 2 PbI 4 MHP originates from crystallographic orientations and chemical composition instability in this material.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-07-2018
Abstract: We report the discovery of room temperature in-plane ferroelectricity in van der Waals In 2 Se 3 with β′ phase.
Publisher: Elsevier BV
Date: 05-2021
Publisher: Wiley
Date: 04-06-2021
Abstract: Metal halide perovskites (MHPs) as one of the most active materials gained tremendous attention in the past decade because of their outstanding performance in optoelectronics. Owing to their perovskite structure, ferroelectricity is anticipated in this class of materials. However, whether MHPs are ferroelectric or not remains elusive. Recently, discussion regarding ferroelasticity in MHPs has been also raised. In addition, ionic motion and structural dynamics are well known in MHPs. The interplay of these phenomena including electric polarization, strain, ionic motion, and structural dynamics can have a significant impact on optoelectronics. Therefore, understanding the mechanism behind these phenomena and their interactions is critical in addressing the controversy about ferroicity of MHPs and developing functional devices. Here, the current findings about MHP's ferroicity are summarized and evaluated and a perspective for the future is provided. It is suggested that ionic motion and associated phenomena, coupled with ferroic behavior, are the main drivers behind MHPs functionality. The challenges are also discussed in probing MHPs’ ferroicity and what new measurement modalities are needed to fully understand and characterize MHP behavior. Finally, it is discussed how ferroic and strain can affect the optoelectronic performance of MHPs and how they can be used for engineering of higher performance devices.
Publisher: AIP Publishing
Date: 03-08-2020
DOI: 10.1063/5.0013847
Abstract: Imaging mechanisms in contact Kelvin probe force microscopy (cKPFM) are explored via information theory-based methods. Gaussian processes are used to achieve super-resolution in the cKPFM signal, effectively extrapolating across the spatial and parameter space. Tensor factorization is applied to reduce the multidimensional signal to the tensor convolution of the scalar functions that show a clear trending behavior with the imaging parameters. These methods establish a workflow for the analysis of the multidimensional datasets that can then be related to the relevant physical mechanisms. We also provide an interactive Google Colab notebook that goes through all the analyses discussed in the paper.
Publisher: Springer Science and Business Media LLC
Date: 19-03-2020
DOI: 10.1038/S41524-020-0289-6
Abstract: We investigate the ability to reconstruct and derive spatial structure from sparsely s led 3D piezoresponse force microcopy data, captured using the band-excitation (BE) technique, via Gaussian Process (GP) methods. Even for weakly informative priors, GP methods allow unambiguous determination of the characteristic length scales of the imaging process both in spatial and frequency domains. We further show that BE data set tends to be overs led in the spatial domains, with ~30% of original data set sufficient for high-quality reconstruction, potentially enabling faster BE imaging. At the same time, reliable reconstruction along the frequency domain requires the resonance peak to be within the measured band. This behavior suggests the optimal strategy for the BE imaging on unknown s les. Finally, we discuss how GP can be used for automated experimentation in SPM, by combining GP regression with non-rectangular scans.
Publisher: Elsevier BV
Date: 02-2020
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Publisher: American Chemical Society (ACS)
Date: 22-05-2019
Publisher: American Chemical Society (ACS)
Date: 13-07-2021
Publisher: Elsevier BV
Date: 11-2021
Publisher: American Chemical Society (ACS)
Date: 14-03-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3TA02565A
Abstract: Our study highlights importance elements of the nanoscale intragrain feature that may pave the way to high-efficiency perovskite solar cells.
Publisher: Elsevier BV
Date: 11-2019
Publisher: American Chemical Society (ACS)
Date: 12-06-2019
Publisher: American Chemical Society (ACS)
Date: 09-10-2019
Abstract: Despite the rapid progress in organic-inorganic halide perovskites (OIHPs) for applications such as solar cells and detectors, knowledge of coupling between electronic and ionic charge carrier dynamics is so far limited. While the presence of dual-conduction channels is widely accepted, the precise physical mechanisms governing the impact of electronic (e.g. electrons and holes) and ionic conduction, especially interface phenomena, remain uncertain. The lack of understanding stems largely from the lack of appropriate tools to capture the electrochemical dynamics on the length scales of the local inhomogeneities present (e.g., interfaces, grain boundaries, space charge regions) and time scales over which the coupled dynamics take place. Here, we implement Kelvin probe force microscopy (KPFM) to explore the charge carrier dynamics at the methylammonium lead tribromide (MAPbBr
Publisher: American Chemical Society (ACS)
Date: 26-05-2021
Publisher: American Chemical Society (ACS)
Date: 30-09-2022
Abstract: The multiple quantum well structure of a quasi-two-dimensional (quasi-2D) perovskite leads to nonradiative Auger recombination (AR). This is due to high local carrier density in recombination centers, although the radiative recombination is improved by efficient energy transfer. In this study, we suppress the AR by introducing phenethylammonium acetate (PEAAc) into the quasi-2D PEA
Publisher: American Chemical Society (ACS)
Date: 30-11-2021
Publisher: Elsevier BV
Date: 10-2021
No related grants have been discovered for Dohyung Kim.