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Van Nguyen Tuan,Do Ha Huu,Tekalgne Mahider,Van Le Quyet,Nguyen Thang Phan,Hong Sung Hyun,Cho Jin Hyuk,Van Dao Dung,Ahn Sang Hyun,Kim Soo Young 나노기술연구협의회 2021 Nano Convergence Vol.8 No.33
Following publication of the original article [1], the affiliation of the authors was incorrectly published in the article. The affiliation which was shown in supplementary information is correct. This has been corrected with this erratum.
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Dual use of tantalum disulfides as hole and electron extraction layers in organic photovoltaic cells
Le, Quyet Van,Nguyen, Thang Phan,Choi, Kyoung Soon,Cho, Yoon-Ho,Hong, Young Joon,Kim, Soo Young The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.46
<P>UV/ozone treated (UVO-treated) TaS<SUB>2</SUB> and non-treated TaS<SUB>2</SUB> nanosheets are introduced into organic photovoltaic cells (OPVs) as hole extraction layers (HEL) and electron extraction layers (EEL). TaS<SUB>2</SUB> nanosheets are obtained <I>via</I> ultrasonic vibration and size-controlled by centrifugation. Atomic force microscopy (AFM) images reveal that the thickness and lateral size of TaS<SUB>2</SUB> nanosheets are approximately 1 and 70 nm, indicating that uniform and ultrathin TaS<SUB>2</SUB> nanosheets are obtained. The work function of TaS<SUB>2</SUB> increases from 4.4 eV to 4.9–5.1 eV after applying UVO treatment by forming Ta<SUB>2</SUB>O<SUB>5</SUB>. In addition, the power conversion efficiencies of normal OPV with UVO-treated TaS<SUB>2</SUB> and inverted OPV with TaS<SUB>2</SUB> are 3.06 and 2.73%, which are higher than those of OPV without TaS<SUB>2</SUB> (1.56% for normal OPV and 0.22% for inverted OPV). These results indicate that TaS<SUB>2</SUB> is a promising material for HEL and EEL layers in OPVs.</P> <P>Graphic Abstract</P><P>Organic photovoltaic cells with a UVO-treated TaS<SUB>2</SUB> hole extraction layer. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp04412f'> </P>
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Le, Quyet Van,Nguyen, Thang Phan,Jang, Ho Won,Kim, Soo Young The Royal Society of Chemistry 2014 Physical Chemistry Chemical Physics Vol.16 No.26
<P>MoS<SUB>2</SUB> nanosheets obtained through a simple sonication exfoliation method are employed as a hole-extraction layer (HEL) to improve the efficiency and air stability of organic photovoltaic cells (OPVs). The reduction in the wavenumber difference, appearance of a UV-vis peak, and atomic force microscopy images indicate that MoS<SUB>2</SUB> nanosheets are formed through the sonication method. The OPVs with MoS<SUB>2</SUB> layers show a degraded performance with a power conversion efficiency (PCE) of 1.08%, which is lower than that of OPVs without HEL (1.84%). After performing the UV/ozone (UVO) treatment of the MoS<SUB>2</SUB> surface for 15 min, the PCE value increases to 2.44%. Synchrotron radiation photoelectron spectroscopy data show that the work function of MoS<SUB>2</SUB> increases from 4.6 to 4.9 eV upon UVO treatment, suggesting that the increase in the PCE value is caused by the bandgap alignment. Upon inserting poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) between MoS<SUB>2</SUB> and the active layer, the PCE value of the OPV increases to 2.81%, which is comparable with that of the device employing only PEDOT:PSS. Furthermore, the stability of the OPVs is improved significantly when MoS<SUB>2</SUB>/PEDOT:PSS layers are used as the HEL. Therefore, it is considered that the use of UVO-treated MoS<SUB>2</SUB> may improve the stability of OPV cells without degrading the device performance.</P> <P>Graphic Abstract</P><P>A longer lifetime was achieved for devices using MoS<SUB>2</SUB>/PEDOT:PSS layers than for those employing only the PEDOT:PSS layer. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp01598c'> </P>
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Le, Quyet Van,Shin, Jong Wook,Jung, Jin-Hee,Park, Jongee,Ozturk, Abdullah,Kim, Soo Young American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.11
<P>CH3NH3PbBr3 (MAPbBr(3)) materials with perovskite structure were grown by a two-step process using Pb(CH3COO)(2). 3H(2)O and methyl amine bromide (MABr). By changing the concentration of MABr in isopropyl alcohol (IPA) solvent and the annealing temperature, the shape of CH3NH3PbBr3 materials can be controlled to afford nanocubes, nanowires, nanorods, and wrinkled structures. MAPbBr3 with single cubic structure was obtained at a MABr concentration of 3 mg/mL in IPA, and a nanorod array of MAPbBr3 was realized at a MABr concentration of 9 mg/mL in IPA at room temperature. Uniformly wrinkled shapes were formed after the synthesis temperature was increased to 60 and 90 degrees C. The X-ray diffraction patterns, Fourier transform infrared spectra, and X-ray photoelectron spectra of CH3NH3PbBr3 nanorods confirmed that the pure perovskite phase was obtained by dipping Pb(CH3COO)(2). 3H(2)O in MABr/IPA solution. The optical bandgap of the CH3NH3PbBr3 nanorods was estimated from the Tauc plot as 2.2 eV. The evolution of perovskite shapes is expected to lead to improvements in the electrical properties and surface contact, which are important factors for realizing high-performance devices.</P>
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WS2–WC–WO3 nano-hollow spheres as an efficient and durable catalyst for hydrogen evolution reaction
Van Nguyen Tuan,Do Ha Huu,Tekalgne Mahider,Van Le Quyet,Nguyen Thang Phan,Hong Sung Hyun,Cho Jin Hyuk,Van Dao Dung,Ahn Sang Hyun,Kim Soo Young 나노기술연구협의회 2021 Nano Convergence Vol.8 No.28
Transition metal dichalcogenides (TMDs), transition metal carbides (TMCs), and transition metal oxides (TMOs) have been widely investigated for electrocatalytic applications owing to their abundant active sites, high stability, good conductivity, and various other fascinating properties. Therefore, the synthesis of composites of TMDs, TMCs, and TMOs is a new avenue for the preparation of efficient electrocatalysts. Herein, we propose a novel low-cost and facile method to prepare TMD–TMC–TMO nano-hollow spheres (WS 2 –WC–WO 3 NH) as an efficient catalyst for the hydrogen evolution reaction (HER). The crystallinity, morphology, chemical bonding, and composition of the composite material were comprehensively investigated using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The results confirmed the successful synthesis of the WS 2 –WC–WO 3 NH spheres. Interestingly, the presence of nitrogen significantly enhanced the electrical conductivity of the hybrid material, facilitating electron transfer during the catalytic process. As a result, the WS 2 –WC–WO 3 NH hybrid exhibited better HER performance than the pure WS 2 nanoflowers, which can be attributed to the synergistic effect of the W–S, W–C, and W–O bonding in the composite. Remarkably, the Tafel slope of the WS 2 –WC–WO 3 NH spheres was 59 mV dec −1 , which is significantly lower than that of the pure WS 2 NFs (82 mV dec −1 ). The results also confirmed the unprecedented stability and superior electrocatalytic performance of the WS 2 –WC–WO 3 NH spheres toward the HER, which opens new avenues for the preparation of low-cost and highly effective materials for energy conversion and storage applications.
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Low Temperature Solution-Processable Cesium Lead Bromide Microcrystals for Light Conversion
Le, Quyet Van,Lee, Jong Won,Sohn, Woonbae,Jang, Ho Won,Kim, Jong Kyu,Kim, Soo Young The American Chemical Society 2018 CRYSTAL GROWTH AND DESIGN Vol.18 No.5
<P>In this report, we present a new approach for the fabrication and application of Cs<SUB>4</SUB>PbBr<SUB>6</SUB> microcrystals (Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs). The Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs are synthesized via an anti-solvent induced crystallization of PbBr<SUB>2</SUB>:CsBr directly in dimethylsulfoxide (DMSO) by introducing HBr (HBr, 48% aqueous solution). The ratio of HBr and DMSO plays a vital role in the formation of Cs<SUB>4</SUB>PbBr<SUB>6</SUB>. By controlling the HBr/DMSO ratio, pure Cs<SUB>4</SUB>PbBr<SUB>6</SUB> or the CsPbBr<SUB>3</SUB> phase can be obtained. The Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs were initially obtained by adding HBr to CsBr:PbBr<SUB>2</SUB>/DMSO. However, on increasing the amount of the added HBr, Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs were converted to CsPbBr<SUB>3</SUB> MCs and the photoluminescence (PL) disappeared. It was also found that CsPbBr<SUB>3</SUB> MCs can be transformed to Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs by simply adding DMSO to the dried CsPbBr<SUB>3</SUB> MCs. The Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs exhibit a strong PL at 516 nm with a full width at half-maximum of 25 nm regardless of the crystal size (5-10 μm). On using Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs as a light converter in ultraviolet light emitting diodes, a PL intensity that is 3 times higher than that of CsPbBr<SUB>3</SUB> quantum dots based devices could be achieved, unraveling the potential of this material for optoelectronic applications.</P><P>Cs<SUB>4</SUB>PbBr<SUB>6</SUB> microcrystals (MCs) are synthesized through a low temperature solution process using hydrobromic acid and dimethyl sulfoxide. The resulting Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs exhibit bright green luminescence at 516 nm regardless of crystal size. The use of Cs<SUB>4</SUB>PbBr<SUB>6</SUB> MCs as light conversion materials shows 3 times higher photoluminescence than that of CsPbBr<SUB>3</SUB> quantum dots, revealing their potential in optoelectronic devices.</P> [FIG OMISSION]</BR>
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Changes in Income Distribution During the COVID-19 Pandemic: Empirical Evidence from Vietnam
Quyet Thang DAO,Thi Yen LE,Van Hung PHAM 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.1
This study examines changes in income for Vietnam’s service labors during COVID-19. A person’s income depends on several factors, such as educational level, working area, the number of activities creating jobs, the cost of living, investment, etc. This research was based on a survey of 479 workers in Vietnam’s service sector, who were evenly distributed across sectors (tourism and aviation) and workplaces (State and private). Based on the collected data, the REM regression model was used to analyze the factors influencing employee income when COVID-19 took place. The research returns show that the COVID-19 pandemic has had a considerable influence on labor incomes, and there are income disparities that exist between workers by work area and by gender. This study indicates that workers’ wages in Vietnam decreased by an average of 12.22 million VND per month after the outbreak of COVID-19. In addition, the results also show that the income of workers after COVID-19 differs depending on their position (the average salary of laborers working in the public sector is about 3.946 million VND higher than the average salary of laborers in the private sector); furthermore, the incomes of workers also vary by gender.
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Low-dimensional halide perovskites: review and issues
Hong, Kootak,Le, Quyet Van,Kim, Soo Young,Jang, Ho Won The Royal Society of Chemistry 2018 Journal of materials chemistry. C, Materials for o Vol.6 No.9
<P>Halide perovskites are emerging materials for future optoelectronics and electronics due to their remarkable advantages such as a high light absorption coefficient, long charge carrier diffusion length, facile synthesis method, and low cost. As polycrystalline halide perovskite thin films, which have been studied so far, have crucial limitations, low-dimensional halide perovskites have attracted attention due to their unique optical properties and charge transport properties, which have not been observed before. This review highlights the limitations of polycrystalline halide perovskites thin films and the unique characteristics of low-dimensional halide perovskite nanostructures including their electrical, optical, and chemical properties. After introducing the recent developments of various low-dimensional halide perovskite nanostructures including the synthesis methods, their properties, and applications, a brief overview of the challenges of low-dimensional halide perovskites as candidates for future optoelectronics and electronic devices is provided.</P>
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