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Hwang, Dae-Kue,Ko, Byoung-Soo,Jeon, Dong-Hwan,Kang, Jin-Kyu,Sung, Shi-Joon,Yang, Kee-Jeong,Nam, Dahyun,Cho, Soyeon,Cheong, Hyeonsik,Kim, Dae-Hwan Elsevier 2017 Solar energy materials and solar cells Vol.161 No.-
<P><B>Abstract</B></P> <P>In this study, we investigate the electrical, structural, and optical properties of band gap front-graded Cu<SUB>2</SUB>ZnSn(S,Se)<SUB>4</SUB> (CZTSSe) thin films grown by a modified single-step sulfo-selenization process from copper-poor and zinc-rich precursor metallic stacks prepared by co-evaporation. To investigate how the bandgap was graded in connection with the compositional distribution, we calculated the bandgap energy distribution along the film thickness, based on the transmission electron microscopy and energy-dispersive X-ray spectroscopy composition profile. The band gap of the CZTSSe phase with high S content near the surface layer is determined to be 1.161eV. From the surface to the bottom, there is a decrease in the S content of the CZTSSe phase, and the band gap subsequently decreases to, 1.029eV, close to the value of CZTSe. From the results of dimpling-Raman and scanning transmission electron microscopy line scanning, we confirm that the S content drastically increases from the bottom to the top surface of the CZTSSe thin film. The CZTSSe thin-film solar cell exhibits a power conversion efficiency (PCE) of 10.33%, with an open-circuit voltage (<I>V</I> <SUB> <I>oc</I> </SUB>) of 0.505 V, short-circuit current density (<I>J</I> <SUB> <I>sc</I> </SUB>) of 31.61mA/cm<SUP>2</SUP>, fill factor (FF) of 64.6%, and <I>V</I> <SUB> <I>oc</I> </SUB> deficit of 525mV. Compared with the performance of the CZTSe solar cell, which had PCE of 7.23%, <I>V</I> <SUB> <I>oc</I> </SUB> of 0.424 V, <I>J</I> <SUB> <I>sc</I> </SUB> of 32.83mAcm<SUP>−2</SUP>, FF of 51.9%, and <I>V</I> <SUB> <I>oc</I> </SUB> deficit of 576mV, the <I>V</I> <SUB> <I>oc</I> </SUB> and <I>V</I> <SUB> <I>oc</I> </SUB> deficit of the CZTSSe cell improved considerably. The high <I>V</I> <SUB> <I>oc</I> </SUB>, low <I>V</I> <SUB> <I>oc</I> </SUB> deficit, and less loss of <I>J</I> <SUB> <I>sc</I> </SUB> are attributed to the effect of band gap front-grading induced by S grading into the CZTSSe thin film.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We investigate the properties of band gap front-graded CZTSSe thin films. </LI> <LI> The precursors are annealed by a modified single-step sulfo-selenization process. </LI> <LI> The CZTSSe thin-film solar cell exhibits power conversion efficiency of 10.33%. </LI> <LI> The high <I>V</I> <SUB> <I>oc</I> </SUB> and less loss of <I>J</I> <SUB> <I>sc</I> </SUB> are attributed to the band gap front-grading. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hwang, Dae-Kue,Nam, Jung Eun,Jo, Hyo Jeong,Sung, Shi-Joon Elsevier Sequoia 2017 Journal of Power Sources Vol. No.
<P><B>Abstract</B></P> <P>In traditional dye-sensitized solar cells (DSSCs), the liquid electrolyte (LE) presents a problem for long-term stability. Herein, we demonstrate a bifacial DSSC by combining a new metal-free organic dye and a quasi-solid state electrolyte (QSSE) that contains poly(vinylidenefluoride-<I>co</I>-hexafluoropropylene) (PVdF-HFP)-based polymer gel. The incident light irradiates the front side of the DSSC, and the transmitted light is reused after reflection on the back side. Owing to the semi-transparent DSSC electrode, the reflected light can penetrate and be absorbed by the dye molecules in the DSSC, thereby enhancing the short-circuit current density and thus the overall power conversion efficiency (PCE). The PCE for the DSSC device with QSSE from bifacial irradiation is 10.37%, a value that is comparable to that obtained with LE-based DSSC (9.89%). The stability of the device is enhanced when the polymer gel containing PVdF-HFP is mixed with the LE, and the effectiveness of PVdF-HFP as a gelator is attributed to its interaction with the Li<SUP>+</SUP> ions. Based on our preliminary results, this architecture can lead to more stable bifacial QSSE-based DSSCs without sacrificing the photovoltaic performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We demonstrate a bifacial DSSC by combining a new metal-free organic dye. </LI> <LI> The reflected light can penetrate and be absorbed by the dye molecules in the DSSC. </LI> <LI> The PCE for the DSSC device with QSSE from bifacial irradiation is 10.37%. </LI> <LI> The stability of the device is enhanced with the polymer gel containing PVDF-HFP. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
黃鎬乙,崔大奎,李龍鶴 全北大學校 1983 論文集 Vol.25 No.-
A study on the reduction of antimony trioxide by hydrogen was carried out to investigate the mechanism and kinetics of antimony trioxide. Possible mechanism for the reaction was discussed with the experimental kinetic data obtained in this investigation. The results obtained in this study are as follows: 1) The rate of reduction was increasing by raising the reaction temperature and hydrogen gas flow rate. 2) The overall reaction rate was controlled by the chemical reaction and the activation energy was about 39.0㎉/㏖. 3) Among the additives, PbO promotes the reduction rate of Sb_2O_3, but CaO and SiO_2 did not effect the reduction of Sb_2O_3 and CaO influenced the grain growth of Sb metal reduced.
Jeon, Dong-Hwan,Hwang, Dae-Kue,Kim, Dae-Hwan,Kang, Jin-Kyu,Lee, Chang-Seop American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.5
<P>We evaluated a ZnS buffer layer prepared using a chemical bath deposition (CBD) process for application in cadmium-free Cu(In,Ga)Se-2 (CIGS) solar cells. The ZnS buffer layer showed good transmittance (above 90%) in the spectral range from 300 to 800 nm and was non-toxic compared with the CdS buffer layers normally used in CIGS solar cells. The CBD process was affected by several deposition conditions. The deposition rate was dependent on the ammonia concentration (complexing agent). When the ammonia concentration was either too high or low, a decrease in the deposition rate was observed. In addition, post heat treatments at high temperatures had detrimental influences on the ZnS buffer layers because portions of the ZnS thin films were transformed into ZnO. With optimized deposition conditions, a CIGS solar cell with a ZnS buffer layer showed an efficiency of 14.18% with a 0.23 cm(2) active area under 100 mW/cm(2) illumination. 4</P>
조현준,김대환,Chan Kim,Dae-Kue Hwang,성시준,Jeong-Hwa Kim,배인호 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.10
The purpose of the present study is to investigate the optical and the structural properties of CuIn1−xGaxSe2 (CIGS) thin films with various Ga/[In+Ga] ratios grown by using the coevaporation technique. The Ga ratios were 0, 0.15, 0.29, 0.40, 0.56, 0.73, and 1. As the Ga/[In+Ga] ratio increased, the grain size of CIGS films decreased, and the X-ray diffraction (XRD) peaks of the CIGS films progressively shifted to higher diffraction angles. In the cross-sectional scanning electron microscopy (SEM) images, the grain size of the CIGS thin films near the molybdenum electrode was smaller than it was near the CIGS surface. These results indicate that the diffusion rates of elements were different. The photocurrent (PC) spectra also showed that the band gap energy of the CIGS films increased as the Ga/[In+Ga] ratio increased. Accordingly, the short-circuit current density (JSC) linearly decreased, and the open-circuit voltage (VOC) increased and saturated at high Ga/[In+Ga] ratios (x > 0.4) due to the defects on the CIGS films surface. A correlation between the Ga/[In+Ga] ratio and the number of surface defects for the CIGS films is discussed.
Byoung-Soo Ko,Dae-Hwan Kim,Dae-Kue Hwang,Seoung-Jun Lee,Jong Su Kim 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.82 No.-
In this study, we investigated the electrical and structural properties of sulfur-graded Cu2ZnSn(S,Se)4(CZTSSe) thinfilms grown using a modified two-step process according to the annealing temperature. The sulfur content of the CZTSSe thinfilm was increased with annealing temperature and a Zn(S, Se)secondary phase was observed at temperatures higher than 500 C. The Raman spectrum of the CZTSSethinfilm shifted continuously toward the high frequency direction with increasing S content and theCu2SnSe3 (CTSe) secondary phase was present below 440 C. From the results of dimpling Ramanspectroscopy and scanning transmission electron microscopy (STEM) line scanning, we confirmed thatthe S content increased gradually from the Mo back contact to the surface of the CZTSSe thinfilm. Finally,a sulfur-graded CZTSSe thinfilm with a photovoltaic efficiency of 7.03% was fabricated by optimizing theannealing temperature.
Eui Jin Lee,Dae-Hwan Kim,Dae-Kue Hwang 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.90 No.-
Inorganic perovskite solar cells (PSCs) are considered prospective alternatives to organic PSCs due to theirefficiency and relative stability. Cesium lead bromide (CsPbBr3) has a complete perovskite structure, isphase stable, exhibits a wide bandgap energy of 2.3 eV under operating conditions, and is regarded as asuitable material not only for stable PSCs, but also for semi-transparent PSCs. In this study, we synthesizeCu–Zn–In–S–Se (CZISSe) quantum dots (QDs) and demonstrate their novel use for improving theperformance of PSC devices. QDs are embedded through ligand-exchange, which replaces long organicchains with thiosulfate (–S2O3) ligands and disperses the S2O3-capped QDs in the PbBr2 solution toprepare QD-blended precursor inks. The QDs promote the crystallization of CsPbBr3 and hole extractionfrom the photoactive layer. As a result, the optimized power conversion efficiency (PCE) of the QDincorporatedPSC is 5.37%, which is a 22.6% enhancement compared to those of the control devices. Thiswork provides an effective and simple process for enhancing the performance of CsPbBr3-based PSCs.