• 한국세라믹학회지
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• 제49권2호
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• pp.135-141
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• 2012

To improve the visible-light induced photocatalytic application performances of $TiO_2$, in this study, the $NiS_2$ modied $TiO_2$ composites were prepared by two methods: hydrothermal method and sol-gel method. The composites were denoted as hs-$NiS_2$/$TiO_2$, and sg-$NiS_2$/$TiO_2$ and characterized by XRD, UV-vis absorbance spectra, SEM, TEM, EDX, and BET analysis. The photocatalytic activities under visible light were investigated by the degradation of methyl orange (MO). The photodegradation rate of methyl orange under visible light with $NiS_2$/$TiO_2$ composites was markedly higher than that of pure $TiO_2$, and the effect of hs-$NiS_2$/$TiO_2$ composites was better than that of sg-$NiS_2$/$TiO_2$. The results indicate that the hydrothermal process could partly inhibit the agglomeration of $NiS_2$/$TiO_2$. Thus, the dispersion of nanoparticles was improved, and that the promoting effect of $NiS_2$ could extend the light absorption spectrum toward the visible region.

• JSTS:Journal of Semiconductor Technology and Science
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• 제8권1호
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• pp.21-26
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• 2008

We fabricated nano-particles of ZnO, $In_2O_3$ and $SnO_2$ by using the chemical reaction between metal thin films and polyamic acid. The average size and density of these ZnO, $In_2O_3$ and $SnO_2$ nano-particles was approximately 10, 7, and 15 nm, and $2{\times}10^{11},\;6{\times}10^{11},\;2.4{\times}10^{11}cm^{-2}$, respectively. Then, we fabricated nano-floating gate memory (NFGM) devices with ZnO and $In_2O_3$ nano-particles embedded in the devices' polyimide dielectrics and silicon dioxide layers as control and tunnel oxides, respectively. We measured the current-voltage characteristics, endurance properties and retention times of the memory devices using a semiconductor parameter analyzer. In the $In_2O_3$ NFGM, the threshold voltage shift (${\Delta}V_T$) was approximately 5 V at the initial state of programming and erasing operations. However, the memory window rapidly decreased after 1000 s from 5 to 1.5 V. The ${\Delta}V_T$ of the NFGM containing ZnO was approximately 2 V at the initial state, but the memory window decreased after 1000 s from 2 to 0.4 V. These results mean that metal-oxide nano-particles have feasibility to apply NFGM devices.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.65-65
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• 2012

Copper zinc tin sulfide ($Cu_2ZnSnS_4$, CZTS) is a very promising material as a low cost absorber alternative to other chalcopyrite-type semiconductors based on Ga or In because of the abundant and economical elements. In addition, CZTS has a band-gap energy of 1.4~1.5eV and large absorption coefficient over ${\sim}10^4cm^{-1}$, which is similar to those of $Cu(In,Ga)Se_2$(CIGS) regarded as one of the most successful absorber materials for high efficient solar cell. Most previous works on the fabrication of CZTS thin films were based on the vacuum deposition such as thermal evaporation and RF magnetron sputtering. Although the vacuum deposition has been widely adopted, it is quite expensive and complicated. In this regard, the solution processes such as sol-gel method, nanocrystal dispersion and hybrid slurry method have been developed for easy and cost-effective fabrication of CZTS film. Among these methods, the hybrid slurry method is favorable to make high crystalline and dense absorber layer. However, this method has the demerit using the toxic and explosive hydrazine solvent, which has severe limitation for common use. With these considerations, it is highly desirable to develop a robust, easily scalable and relatively safe solution-based process for the fabrication of a high quality CZTS absorber layer. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 1.5~2.0 ${\mu}m$ and micrometer-scaled grains using two different non-vacuum approaches. The first solution-processing approach includes air-stable non-toxic solvent-based inks in which the commercially available precursor nanoparticles are dispersed in ethanol. Our readily achievable air-stable precursor ink, without the involvement of complex particle synthesis, high toxic solvents, or organic additives, facilitates a convenient method to fabricate a high quality CZTS absorber layer with uniform surface composition and across the film depth when annealed at $530^{\circ}C$. The conversion efficiency and fill factor for the non-toxic ink based solar cells are 5.14% and 52.8%, respectively. The other method is based on the nanocrystal dispersions that are a key ingredient in the deposition of thermally annealed absorber layers. We report a facile synthetic method to produce phase-pure CZTS nanocrystals capped with less toxic and more easily removable ligands. The resulting CZTS nanoparticle dispersion enables us to fabricate uniform, crack-free absorber layer onto Mo-coated soda-lime glass at $500^{\circ}C$, which exhibits a robust and reproducible photovoltaic response. Our simple and less-toxic approach for the fabrication of CZTS layer, reported here, will be the first step in realizing the low-cost solution-processed CZTS solar cell with high efficiency.