Publications by authors named "Tack Lee"

Solar fuel production involving the conversion of solar energy directly into chemical fuels such as hydrogen and valuable chemicals using photoelectrochemical (PEC) cells and photocatalysts (PCs) offers a promising avenue for sustainable energy while reducing carbon emissions. However, existing PEC cells and PCs fall short of economic viability due to their low solar-to-chemical (STC) conversion efficiency associated with the employed semiconductors, highlighting the clear need for identifying ideal semiconductor materials. Organic semiconductors (OSs), π-conjugated carbon-based materials, have emerged as promising candidates for enhancing STC conversion efficiency due to their remarkable optoelectrical properties, which can be readily adjustable through molecular engineering.

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Organic photovoltaics (OPVs) have recently shown substantial progress in enhancing device efficiency, driven in particular by advances in the design of nonfullerene acceptors and the reduction of the energy offset driving exciton separation at the donor/acceptor interface. Herein, we employ temperature-dependent transient absorption spectroscopy to investigate the activation energy for charge generation and recombination in a range of bulk heterojunction blends with nonfullerene acceptors. Remarkably, we find that in all cases charge generation is almost activationless, in the range of 11-21 meV, independent of energetic offset.

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Purpose: The rapid expansion of robotic surgical equipment necessitates a review of the needs and challenges faced by hospitals introducing robots for the first time to compete with experienced institutions. The aim of this study was to analyze the impact of robotic surgery on our hospital compared to open and laparoscopic surgery, examine internal transformations, and assess regional, domestic, and international implications.

Methods: A retrospective review was conducted of electronic medical records (EMRs) from 2019 to 2022 at Inha University Hospital, including patients who underwent common robotic procedures and equivalent open and laparoscopic operations.

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Photoelectrochemical (PEC) devices offer a promising platform toward direct solar light harvesting and chemical storage through artificial photosynthesis. However, most prototypes employ wide bandgap semiconductors, moisture-sensitive inorganic light absorbers, or corrosive electrolytes. Here, the design and assembly of PEC devices based on an organic donor-acceptor bulk heterojunction (BHJ) using a carbon-based encapsulant are introduced, which demonstrate long-term H evolution and CO reduction in benign aqueous media.

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A bulk-heterojunction (BHJ) blend is commonly used as the photoactive layer in organic photodetectors (OPDs) to utilize the donor (D)/acceptor (A) interfacial energetic offset for exciton dissociation. However, this strategy often complicates optimization procedures, raising serious concerns over device processability, reproducibility, and stability. Herein, highly efficient OPDs fabricated with single-component organic semiconductors are demonstrated via solution-processing.

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The non-fullerene acceptors (NFAs) employed in state-of-art organic photovoltaics (OPVs) often exhibit strong quadrupole moments which can strongly impact on material energetics. Herein, we show that changing the orientation of Y6, a prototypical NFA, from face-on to more edge-on by using different processing solvents causes a significant energetic shift of up to 210 meV. The impact of this energetic shift on OPV performance is investigated in both bilayer and bulk-heterojunction (BHJ) devices with PM6 polymer donor.

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Semiconducting lead halide perovskite nanocrystals (PNCs) are regarded as promising candidates for next-generation optoelectronic devices due to their solution processability and outstanding optoelectronic properties. While the field of light-emitting diodes (LEDs) and photovoltaics (PVs), two prime examples of optoelectronic devices, has recently seen a multitude of efforts toward high-performance PNC-based devices, realizing both devices with high efficiencies and stabilities through a single PNC processing strategy has remained a challenge.  In this work, diphenylpropylammonium (DPAI) surface ligands, found through a judicious ab-initio-based ligand search, are shown to provide a solution to this problem.

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We investigate the photovoltaic characteristics of organic solar cells (OSCs) for two distinctly different nanostructures, by comparing the charge carrier dynamics for bilayer- and bulk-heterojunction OSCs. Most interestingly, both architectures exhibit fairly similar power conversion efficiencies (PCEs), reflecting a comparable critical domain size for charge generation and charge recombination. Although this is, at first hand, surprising, a detailed analysis points out the similarity between these two concepts.

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Among various potential applications of organic photovoltaics (OPVs), indoor power generation has great potential because of several advantages over outdoor light harvesting under 1 sun conditions. Commonly used indoor light sources have narrower emission spectra with lower intensity (by 3 orders of magnitude) as compared to the solar spectrum. Highly tunable optical absorption, large absorption coefficients, and small leakage currents under dim lighting conditions make OPVs promising candidates for indoor applications.

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Müllerian duct aplasia-renal aplasia-cervicothoracic somite dysplasia (MURCS) association is a unique development disorder with four common types of malformations that include uterine aplasia or hypoplasia, renal ectopy or agenesis, vertebral anomalies, and short stature. The majority of MURCS patients are diagnosed with primary amenorrhea from late-adolescence. However, a few cases with MURCS association are not well diagnosed during childhood and long-term outcomes are not well reported.

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AMP-activated protein kinase (AMPK) has been implicated in contractility changes in bladders with partial bladder outlet obstruction (PBOO), but the role of AMPK in the contractile response of normal bladder remains unclear. We investigated the phosphorylation of AMPKα and expression of the involved upstream AMPK kinases (AMPKKs) in a model of bladders with PBOO and sought to determine whether the pharmacological inhibition of these two factors affected detrusor contractility in normal bladders, using female Sprague-Dawley rats. Cystometry and Western blot analysis were performed in rats that were subjected to PBOO induction or a sham operation.

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In the field of organic solar cells, it has been generally accepted until recently that a difference in band energies of at least 0.3 eV between the highest occupied molecular orbital (HOMO) level of the donor and the HOMO of the acceptor is required to provide adequate driving force for efficient photoinduced hole transfer due to the large binding energy of excitons in organic materials. In this work, we investigate polymeric donor:non-fullerene acceptor junctions in binary and ternary blend polymer solar cells, which exhibit efficient photoinduced hole transfer despite negligible HOMO offset and demonstrate that hole transfer in this system is dependent on morphology.

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Urine metabolites are used in many clinical and biomedical studies but usually only for a few classic compounds. Metabolomics detects vastly more metabolic signals that may be used to precisely define the health status of individuals. However, many compounds remain unidentified, hampering biochemical conclusions.

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The ability to control the morphologies of active layers is a critical factor in the successful development of polymer solar cells (PSCs), and solvent processing additives offer a simple and effective way to accomplish this. In particular, diphenyl ether (DPE) is one of the most effective solvent additives but analogous additives based on this structure have not yet been extensively investigated. In this work, we have fabricated PSCs and investigated photovoltaic device characteristics using the series of non-halogenated, diphenyl-chalcogen solvent additives; DPE, diphenyl sulfide (DPS) and diphenyl selenide (DPSe).

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We synthesized three semicrystalline polymers (PTTBT, PDTBT, and P2FDTBT) by modulating the intra- and intermolecular noncovalent Coulombic interactions and investigated their photovoltaic characteristics under various light intensities. Low series (R) and high shunt (R) resistances are essential prerequisites for good device properties under standard illumination (100 mW cm). Considering these factors, among three polymers, PDTBT polymer solar cells (PSCs) exhibited the most desirable characteristics, with peak power conversion efficiencies (PCE) of 7.

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Purpose: The pathophysiological role of detrusor overactivity (DO) in the bladder, which is commonly observed in various bladder diseases, is not well understood. DO appears in bladder outlet obstruction (BOO), and may continue even after subsequent deobstruction. DO therefore provides an excellent opportunity to observe molecular biological changes.

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Interstitial cystitis (IC) is a chronic bladder dysfunction characterized as urinary frequency, urgency, nocturia, and pelvic pain. The changes in urethra may wind up with the bladder changes in structure and functions, however, the functions of the urethra in IC remains elusive. The aim of this study was to understand the perturbed gene expression in urethra, compared with urinary bladder, associated with the defected urodynamics.

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Germanium exhibits high charge capacity and high lithium diffusivity, both are the key requirements for electrode materials in high performance lithium ion batteries (LIBs). However, high volume expansion and segregation from the electrode during charge-discharge cycling have limited use of germanium in LIBs. Here, we demonstrate that ZnO decorated Ge nanoparticles (Ge@ZnO NPs) can overcome these limitations of Ge as an LIB anode material.

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This study on interstitial cystitis (IC) aims to identify a unique urine metabolomic profile associated with IC, which can be defined as an unpleasant sensation including pain and discomfort related to the urinary bladder, without infection or other identifiable causes. Although the burden of IC on the American public is immense in both human and financial terms, there is no clear diagnostic test for IC, but rather it is a disease of exclusion. Very little is known about the clinically useful urinary biomarkers of IC, which are desperately needed.

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