Shi-Joon Sung

Shi-Joon Sung
Daegu Gyeongbuk Institute of Science and Technology | DGIST · Convergence Reserch Center for Solar Energy

About

131
Publications
18,024
Reads
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2,149
Citations
Additional affiliations
September 2007 - present
Daegu Gyeongbuk Institute of Science and Technology
Position
  • Principal Researcher
September 2004 - August 2007
Samsung Electronics
Position
  • Engineer
March 2000 - August 2004
Korea Advanced Institute of Science and Technology
Position
  • PhD Student

Publications

Publications (131)
Article
In this study, we investigated the effect of the stacking order of metal precursors on the formation of volume defects, such as blisters and nanopores, in CZTSSe thin-film solar cells. We fabricated CZTSSe thin films using three types of metal-precursor combinations, namely, Zn/Cu/Sn/Mo, Cu/Zn/Sn/Mo, and Sn/Cu/Zn/Mo, and studied the blister formati...
Article
A uniformly grown Sb2Se3 nanorods array, with the introduction of a MoSe2 interlayer, obtained by a co-evaporation process and its application to three-dimensional (3D) p-n junction high-efficiency Sb2Se3 solar cells...
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Full-text available
The efficiency of thin-film chalcogenide solar cells is dependent on their window layer thickness. However, the application of an ultrathin window layer is difficult because of the limited capability of the deposition process. This paper reports the use of atomic layer deposition (ALD) processes for fabrication of thin window layers for Cu(Inx,Ga1−...
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Improving the efficiency of kesterite (Cu2ZnSn(S,Se)4; CZTSSe) solar cells requires understanding the effects of Na doping. This paper investigates these effects by applying a NaF layer at various positions within precursors. The NaF position is important because Na produces Na‐related defects in the absorber and suppresses the formation of intrins...
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In this paper, we propose an optimized structure of thin Cu(In,Ga)Se2 (CIGS) solar cells with a grating aluminum oxide (Al2O3) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. Al2O3 is used as a rear surface passivation material to reduce carrier recombi...
Article
Numerous methods have been employed for utilizing inorganic thin films to improve the stability of transparent photovoltaics (TPVs). However, the use of these methods was restricted due to limitations involving restricted physical dimensions, complex fabrication processes, visible transparency, and photovoltaic performance. In this study, a novel a...
Article
In this study, to control the formation of non-uniformly distributed large voids and Cu-Sn alloy agglomeration, which leads to local compositional misfit and secondary phase formation, a SnS compound precursor was applied instead of metal Sn to avoid compositional non-uniformity. Using a Cu/Zn/SnS stacked precursor, a temperature tracking experimen...
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By simple soaking titanium dioxide (TiO2) films in an aqueous Na2S solution, we could prepare surface-modified photoanodes for application to dye-sensitized solar cells (DSSCs). An improvement in both the open-circuit voltage (Voc) and the fill factor (FF) was observed in the DSSC with the 5 min-soaked photoanode, compared with those of the control...
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In this paper, we propose that the microstructural control of (hk1) preferentially oriented Sb2Se3 films from flat films to rod arrays can improve their photovoltaic efficiency by maximizing the carrier transport characteristics. We found that, during co-evaporation, there is a narrow substrate temperature window where the Sb2Se3 rod array can be f...
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Stainless steel (SS) foil is made of abundant materials and is a durable and flexible substrate, but its efficiency deteriorates via the diffusion of impurities from the SS substrate into a Cu2ZnSn(S, Se)4 (CZTSSe) absorber layer. In this work, the diffusion barrier for CZTSSe solar cells is investigated by X-ray diffraction (XRD), secondary ion ma...
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We fabricated CZTSSe thin films using optimized SLG-Mo/Zn/Cu/Sn (MZCT) as a stacked structure and described the phenomenon of Zn elemental volatilization using the MZCT stacked structure. We introduced H2S gas to effectively control the S/(S + Se) ratio of the film in the sulfo-selenization process and to suppress Zn volatilization. Unlike during t...
Article
High-voltage operation in LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) is an attractive strategy to meet the demands for practical application of high energy density lithium-ion batteries (LIBs). However, a serious problem at high cut-off voltage is the capacity fading during charge-discharge cycling, caused by electrolyte decomposition and dissolution of c...
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We investigated an electrospray-based method to manufacture photoelectrodes for dye-sensitized solar cells (DSSCs). TiO2 doughnut-, spherical-, and disk-shaped particles with a large surface area, high crystallinity, uniform nanostructure, and good light scattering properties were fabricated via a simple electrospray method. The control of the morp...
Article
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-co-hexafluoropropylene) (PVdF-HFP)-based polymer gel. The inciden...
Article
Herein, we report on the systematic engineering of the interface between the titanium oxide (TiO2) photoelectrode and the antimony sulfide (Sb2S3) absorber layer in planar Sb2S3 solar cells, which was much unexplored, on the photovoltaic performance. Due to simple spin-coating process for the preparation of TiO2 and Sb2S3 layers, it was possible to...
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In this paper, the effect of H2O on the microstructure of block TiO2 (b-TiO2) and PbI2 films during spin coating for perovskite solar cells was investigated. Dense TiO2 and PbI2 films were formed in a N2 glove box regardless of the spinning time; in contrast, porous TiO2 and PbI2 films were formed in a humid atmosphere. The formation mechanism of t...
Article
In this study, we investigate the electrical, structural, and optical properties of band gap front-graded Cu2ZnSn(S,Se)4 (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...
Article
Although the record efficiencies of perovskite hybrid solar cells are gradually reaching the efficiency of crystalline Si solar cells, perovskite hybrid solar cells often exhibit significant current density-voltage (J-V) hysteresis with respect to the forward and reverse scan direction and scan rate. The origin of the J-V hysteresis of perovskite h...
Article
High-quality CH3NH3PbI3 (MAPbI3) crystalline powders were synthesized from a dispersion of MAPbI3 solution in an antisolvent of dichloromethane. They were used as starting chemicals for precursor solutions. The PbI2-DMF(N,N-dimethyformamide)-, perovskite-, and PbI2-MAI(methylammonium iodide)-DMF-dominant phases were preferentially formed under cond...
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To meet the nanofabrication requirements, such as control of structure and scalability, we investigated an electrospray-based method to manufacture scattering layers (SLs) for dye-sensitized solar cells (DSSCs). TiO2 spherical and disk-shaped particles with a large surface area, high crystallinity, uniform nanostructure and good light scattering pr...
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Most previous studies of perovskite films have explored the use of highly (110)-oriented perovskite films, even though films having the (100) orientation exhibit more desirable characteristics. In this study, we examined a simple method for growing (100)-oriented perovskite films for solar cells and elucidated their growth mechanism. Oriented perov...
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The Cu2ZnSnS4 thin film is a well-known and promising electrode material to substitute for the expensive Pt counter electrode used in dye-sensitized solar cells. In this work, we have proposed a novel nanoporous Cu2ZnSnS4 thin film prepared by a simple and non-toxic process for use as the counter-electrode material. The Cu2ZnSnS4 thin film was easi...
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Solution-processed Cu2ZnSnS4 (CZTS) thin films are generally fabricated by sulfurization of CZTS precursor films. Therefore, the sulfurized CZTS thin films are closely affected by the thin film properties of the CZTS precursor films. In this work, we have investigated the correlation between the thin film properties of the CZTS precursor films prep...
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We adopted an embedded photoelectrode, which consisted of a composite of TiO2 nanotubes (NTs) and nanoparticles (NPs) in a Ti-foil substrate to improve the cell efficiency of conventional TiO2 NP-based dye-sensitized solar cells (DSSCs) with Ti-foil substrates. The resulting increase in short-circuit current density (J sc) of the embedded-TiO2-NT-N...
Article
In order to reduce the interfacial charge recombination between photoinjected electrons and triiodide ions in the electrolyte, a TiO2 surface was modified with potassium permanganate (PM). The PM-modified TiO2 electrodes were prepared by soaking the TiO2 films in an aqueous PM solution, and the resulting electrodes were applied to the photoanodes o...
Article
The inorganic semiconductor Sb2S3 is a representative absorber material for inorganic–organic hybrid solar cells. Till date, Sb2S3 is normally deposited by the chemical bath deposition (CBD) method. However, the formation of antimony oxides cannot be avoided by the conventional CBD method, resulting in deep traps and causing a backward recombinatio...
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The power conversion efficiency of lead halide perovskite solar cells recently surpassed 22.1%. In this study, we suggest the perovskite absorber growth mechanism of the two-step process could be explained by an Ostwald ripening growth model for planar-structure perovskite solar cells. We attempt to find out the source of two main problems such as...
Article
Photovoltaic performance of dye-sensitized solar cells (DSSCs) with a mixed overlayer composed of TiO2 and MgO was investigated in detail. The surface of photoelectrode (TiO2) films was modified with a TiCl4:MgCl2 mixed aqueous solutions with various molar ratios and then calcining to produce the surface-modified TiO2 photoelectrodes (Ti:Mg-TiO2/FT...
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Solution-based Cu2ZnSnS4 (CZTS) solar cells are attracting a lot of attention as a strong alternative to vacuum-based CZTS solar cells owing to their simple and low-cost process, large area deposition, and so on. Typically, the solution-based process consists of two steps: coating with precursor solution and annealing of the precursor films. Unlike...
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Although Cu2ZnSn(S,Se)4 (CZTSSe) has attracted attention as an alternative to CuInGaSe2 (CIGS) as an absorber material in solar cells, its low efficiency is a serious shortcoming preventing its commercialization. To realize a high-efficiency CZTSSe solar cell, improved grain crystallinity, inhibited secondary-phase formation, controlled defect gene...
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In a dye-sensitized solar cell (DSSC) consist of a TiO2 nanostructured photoelectrode, the other components are the electrolyte and the counter electrode. Dye molecules adsorbed onto the surface of the TiO2 photoelectrode provide electrons; thus, the photoelectrode determines the performance of the cell. TiO2 photoelectrodes for DSSCs can be fabric...
Article
Bilayer type CH3NH3PbI3 (MAPbI3) perovskite hybrid solar cells were fabricated via a one-step spin-coating process by using solubility controlled MAPbI3 solutions of MAPbI3-DMSO (dimethyl sulfoxide) and MAPbI3-DMF (N, N-dimethylformamide)-HI. The best DMSO-bilayer device showed 1.07 ± 0.02 V V oc (open-circuit voltage), 20.2 ± 0.1 mA cm(-2) J sc (s...
Article
The surface of a TiO2 photoelectrode was modified through a dip-coating process using an aqueous potassium nitrate (KNO3) solution to increase the power-conversion efficiency of dye-sensitized solar cells (DSSCs). The KNO3-modified TiO2 electrode was applied to the photoanode of the DSSCs. The DSSC with the KNO3-modified TiO2 electrode exhibited a...
Article
We applied potassium water glass (PWG) for a modification of photoelectrodes and investigated the effects of this modification on the photovoltaic properties of dye-sensitized solar cells (DSSCs). The PWG-modified TiO2 electrodes were prepared by soaking the TiO2 films in an aqueous PWG solution, and the resulting electrodes were applied to the pho...
Article
Nanostructured TiO2 films with a double-layered structure are prepared by a facile one-step soaking method. We have investigated the morphology of nanostructured TiO2 films according to the reaction time, concentration of the reactant, and reaction temperature of the soaking reaction, which all have a significant effect on the thickness and layered...
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We have studied the effect of TiCl4 post-treatment on the embedded-type TiO2 nanotubes (NT)-dyesensitized solar cells (DSSCs). The TiO2 nanoparticles layer formed on TiO2 NTs surface by TiCl4 post-treatment showed different morphologies depending on TiCl4 treatment temperature. These different morphologies influenced the cell efficiency of TiO2 NT-...
Article
As a surface modifier, sodium dodecyl sulfate (SDS), was applied to dye-sensitized solar cells (DSSCs), and its effects on the photovoltaic performance of the solar cells were investigated. When the SDS was co-adsorbed with dye (N719) onto TiO2 surface, the DSSCs with SDS showed an increase in short-circuit current (J sc), open-circuit voltage (V o...
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We have investigated the effects of adding (Ta) ions to InSnO thin films by co-sputtering on the performance of InSnO thin film transistors (TFTs). TaInSnO TFTs exhibited significantly lower off currents and higher on/off current ratios. Ta ions, owing to their strong affinity to oxygen suppress the formation of free electron carriers in thin films...
Article
Raman scattering and atomic force microscopy measurements on Cu2ZnSnS4 thin films prepared by a direct solution method revealed that metal sulfates of various morphologies (dense clusters or separated particles) were partially embedded on the surface of the Cu2ZnSnS4 layer. This residue was removed during the subsequent chemical bath deposition of...
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Nanoporous p-type semiconductor thin films are prepared by simple solution-based process with appropriate thermal treatment and three-dimensional (3D) p-n junction solar cells fabricated by depositing n-type semiconductor layers onto the nanoporous p-type thin films shows considerable photovoltaic performance compared with conventional thin film p-...
Article
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Cu2ZnSnS4 (CZTS) solar cells are attracting significant attention as an alternative to CIGS (CuIn1-x Ga x S2) solar cells because of the non-toxic and inexpensive constituent elements of CZTS. Recently, solution-based deposition methods are being developed because they have advantages such as suitability for use in large-area deposition, high-throu...
Article
CuIn X Ga1-X Se2 (CIGS) thin films were prepared by a solution-based CuInGa (CIG) precursorselenization process. First, we investigated the effect of selenization temperature on the formation of polycrystalline CIGS and grain growth. The CIG precursor films were selenized using a two-step process to investigate the reaction of Se and CIG precursors...
Article
Sub-micron thick Cu(In,Ga)Se2 (CIGS) thin films were deposited on Mo-coated soda-lime glass substrates under various conditions by single-stage co-evaporation. Generally, the short circuit current (Jsc) decreased with the decreasing thickness of the absorber layer. However, in this study, Jsc was nearly unchanged with decreasing thickness, while th...
Article
The efficiency of polymer solar cells (PSCs) with P3HT [poly(3-hexyl thiophene)]:PC61BM [[6,6]-phenyl C61-butyric acid methyl ester] blend film was improved by the incorporation of a fluorocyanophenyl compound, 3,4,5,6-tetrafluorophthalonitrile (TFP), as an additive. When the amount of TFT additive was 5 wt% based on the total amount of P3HT and PC...
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A mesoporous TiO2 photo-electrode for dye-sensitized solar cells (DSSCs) was fabricated by an electrospray method using a solution of dispersed TiO2 nanocrystals (P25). A mesoporous TiO2 disk has a larger surface area than P25. The sub micrometer-sized TiO2 disk promotes light scattering, thereby increasing the photocurrent conversion efficiency. H...
Article
Nanostructured TiO2 films were prepared by a one-step soaking method, which has many advantages, such as simple fabrication, a short reaction time, and fast growth. We have investigated the growth of TiO2 films by the substrate orientation of the soaking method, which had an effect on the nanostructure of the TiO2 films. The TiO2 films prepared by...
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Full-text available
In this work, we have fabricated thin film transistors (TFTs) using amorphous tantalum indium zinc oxide (a-TaInZnO) channels by the co-sputtering process. The effects of incorporating tantalum on the InZnO material were investigated using Hall-effect measurement results, and electrical characteristics. We also found that the carrier densities of t...
Article
Nanostructured TiO2 films with double-layered structure are prepared by a facile one-step soaking method. We have investigated the morphology of nanostructured TiO2 films by the reaction time of the soaking method, which has an effect on the thickness and layered structure of the TiO2 films. The TiO2 films prepared by this method have a unique doub...
Article
Poly(diallyldimethylammonium chloride) (PDAC), a water-soluble polyelectrolyte, is used as the electron collecting layer (ECL) on indium tin oxide (ITO) for inverted polymer solar cells (PSCs) with poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71 BM) as the active materials. PDAC is coated directly on top of the IT...
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A high-quality Sb2S3 thin-absorber with controllable thickness was reproducibly formed by atomic layer deposition (ALD) technique. Compared with conventional chemical bath deposition (CBD), the Sb2S3 absorber deposited by ALD did not contain oxide or oxygen impurities and showed very uniform thickness of Sb2S3 absorbers formed on rough surface of d...
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A hot-pressing process is shown to enhance the adhesion of TiO2 nanofibers electrospun onto fluorine-doped tin oxide substrates for use in dye-sensitized solar cells. By using the resulting electrochemical impedance spectroscopic characteristics, the application of 7, 14, and 21 MPa of pressure was found to result in calculated lifetimes of 7.48, 1...
Article
Cu2ZnSnS4 (CZTS)-based materials have a useful band gap and a high absorption coefficient; however, their power conversion efficiency is low compared with that of CdTe and Cu(In,Ga)Se2-based solar cells. Two of the factors that strongly affect CZTS solar cell characteristics are the MoS2 layer and the presence of defects. In this study, Mo back-con...
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We have investigated the optical properties of CuIn1−xGaxSe2 (CIGS) thin film solar cells using their electroreflectance (ER) at room temperature. The ER spectra exhibited one broad and two narrow signal regions. Using the photoluminescence (PL) and photocurrent (PC) spectra, the peaks in the low-energy region (1.02–1.35 eV) can be assigned to the...
Article
Lattice-patterned liquid crystal (LC)–polymer composites are representative candidates for the practical application of LC materials in high-quality flexible displays. In this work, multicomponent prepolymers are used for the fabrication of lattice-patterned LC–polymer composites via photoinduced phase separation. Phase separation behavior between...
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Full-text available
We studied how to effectively add/remove organic chemicals to/from CZTS precursor thin films to prepare uniform CZTS thin films that show optimal properties. We used multi-functional thiourea, as both a stabiliser and a source of sulphur, to prepare the precursor solutions. This is because it forms complexes with metal chlorides, which stabilise th...
Article
Dye-sensitized solar cells (DSSCs) were fabricated using an additional porous nanocrystalline titanium oxide reflecting layer in order to improve light harvesting properties. Because of the high reflectance and scattering characters of the nanocrystalline titanium oxide, photocurrent conversion efficiency and short circuit current density of DSSCs...
Article
In this study, we have investigated the electrical and structural properties of sub-micron thick Cu(In,Ga)Se-2 (CIGS) films with various in-situ post annealing times. Sub-micron thick CIGS films were deposited on Mo/soda-lime glass (SLG) substrates by single-stage co-evaporation. We decreased the deposition time to 700 s for sub-micron thick CIGS f...