JunHo Kim

Wet chemical synthesis of WO3 thin films for supercapacitor application

Tungstic oxide (WO3) thin films have been synthesized by wet chemical method, i.e., successive ionic layer adsorption and reaction (SILAR) method. These films are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption techniques. The XRD pattern revealed the formation of polycrystalline WO3 films. Scanning electron micrographs demonstrate the three-dimensional aggregated irregular extended rod shaped morphology of WO3 thin films. The WO3 film showed a direct band gap of 2.5 eV. The WO3 film exhibited specific capacitance of 266 F·g−1 in 1 M Na2SO4 electrolyte at the scan rate of 10 mVs−1.

Ge-alloyed CZTSe thin film solar cell using molecular precursor adopting spray pyrolysis approach

We report a promising fabrication approach for the synthesis of Ge-alloyed Cu2Zn(GexSn1−x)Se4 (CZGTSe) thin films using molecular precursors by spray pyrolysis to obtain band gap tuned kesterite solar cells. A stable and well dissolved precursor solution of CZTS/CZGTS with the desired elemental composition is prepared in DMSO solvent, sprayed on a Mo substrate and subsequently selenized under ambient selenium at high temperature to obtain well-crystallized absorber layers. The Ge-alloyed CZTSe thin films had improved surface morphology, grain size and crystal quality, which led to power conversion efficiencies as high as 4.72%. The growth properties and device analysis suggest that enhancement of the device performance can be achieved by further optimization of the absorber and interface layers with mitigation of defect activities.

Cu (InGa) SeTe Nanocrystals Structural and Optical Properties

Cu (InGa) SeTe Nanocrystals Structural and Optical Properties nNovel chalcogenide nanocrystals are the potential materials for the photovoltaic use. Predominantly, single phasic chalcogen materials are an area of the great attention. In this order it is important to demonstrate colloidal synthesis of Cu25(In16Ga9)Se40Te10 (CIGST-1) and Cu20(In14Ga9)Se45Te12 (CIGST-2) nanocrystals adopting the single step heating-up (170oC) process. The synthesized materials single/ multi-phases crystallographic structures are verified from the X-ray diffractometer. The average size agglomerated nanocrystals/ particles is evaluated less than 10 nm from the Transmission Electron Microscopy and VU-Visible spectrum Lorentzian fit analysis. The UV-Visible optical absorption spectrum demonstrates a distinguishable blue shift. While the elemental presence and their particle distribution within the configuration is described with help of the energy dispersive X-ray mapping technique. The materials binding energy core level changes are verified from the X-photoelectron spectroscopy. The photoluminescence spectroscopic outcome is revealed a broad peak in wave length range 450 nm to 750 nm for these materials.