• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.315-320
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• 2020

Methylammonium lead iodide (MAPbI₃) thin films were grown at low temperatures on glass substrates via 3-zone chemical vapor deposition. Lead iodide (PbI₂) and lead bis (dipivaloylmethanate) [Pb(dpm)₂] precursors were used as lead sources. Due to the high sublimation temperature (~400℃) of the PbI₂ precursor, a low substrate temperature could not be constantly maintained. Therefore, MAPbI₃ thin films degraded into the PbI₂ phase. In contrast, for the Pb(dpm)₂ precursor, a substrate temperature of ~120℃ was maintained because the sublimation temperature of Pb(dpm)₂ is as low as 130℃ at a high vapor pressure. As a result, high-quality MAPbI₃ thin films were successfully grown on glass substrates using Pb(dpm)₂. The rms (root-mean-square) roughness of MAPbI₃ thin films formed from Pb(dpm)₂ was as low as ~19.2 nm, while it was ~22.7 nm for those formed using PbI₂. The grain size of the films formed from Pb(dpm)₂ was as large as approximately 350 nm.

• Journal of the Korean Chemical Society
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• v.17 no.5
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• pp.378-384
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• 1973

To investigate the mechanism of the reaction of electrolytic oxidation of iodide to iodate ions, polarization curves are determined in various kinds of solution using electrodeposited lead peroxide and platinum anodes. It was observed from the polarization curves that the limiting current is exists at concentration 1.5 M of potassium iodide, and these limiting current disappeared as potassium hydroxide was added up to concentration of 0.1 M. while in case of platinum anode, limiting current did not appear in dilute potassium iodide solution. These results are owing to the chemical reaction, $PbO_2+2I^{-}+2H^+{\to}PbO+I_2+H_{2}O$ ocurring at the surface of lead peroxide anode. Also, we studied to obtain the optimum conditions of electrolytic preparation of iodate from iodide solution using a cell without the diaphragm. The results are that; (a) addition of potassium dichromate at the anti-reducing agent is proper in concentration of 0.1 g/l, (b) electrolytic temperature is not so much effective in raising the current efficiency, (c) current efficiency is increased with current density, and (d) electrolysis is the most effective in weak alkaline solutions.

• Current Photovoltaic Research
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• v.10 no.4
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• pp.101-106
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• 2022

We prepared a CsPbI₂Br solution using Cesium iodide (CsI), Lead (II) bromide (PbBr₂) and Lead (II) iodide (PbI₂) materials into a polar solvent mixture of N,N-dimethylformamide (DMF) and Dimethyl sulfoxide (DMSO). A simple spin coating technique was used for the fabrication of CsPbI₂Br absorber layer in the solution process. In order to prepare uniform coating of absorber film we adopted a hot-air process in assocation with the spin coating. It was confirmed that the thin film manufactured by the hot-air process had a higher absorption rate than that without it, and the optical band gap was measured 1.93 eV. The thin film of absorber was uniformly prepared and revealed the Black α-Cubic crystal phase as proved through X-ray diffraction analysis. Finally, a perovskite solar cell having an n-i-p structure was manufactured with a CsPbI₂Br perovskite absorption layer. From the solar cell, we obtained a power conversion efficiency (PCE) of 5.97% in a forward measurement.

• Bulletin of the Korean Chemical Society
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• v.27 no.5
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• pp.679-686
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• 2006

The positions of $PbI _2$ molecule synthesized into the molecular-dimensioned cavities of $\mid K_6 (Pb _4I_2)(PbI_2) _{0.67}-(H_2O)_2\mid [Si _{12}Al _{12}O _{48}]$-LTA have been determined. A single crystal of $\mid Pb _6\mid [Si _{12}Al _{12}O _{48}]$-LTA, prepared by the dynamic ion-exchange of $\mid Na _{12}\mid [Si _{12}Al _{12}O _{48}]$-LTA with aqueous 0.05 M $Pb _(NO _3)_2$ and washed with deionized water, was placed in a stream of flowing aqueous 0.05 M KI at 294 K for three days. The resulting crystal structure of the product $( \mid K_6 (Pb _4I_2)(PbI_2) _{0.67}(H_2O)_2\mid [Si _{12}Al _{12}O _{48}]$-LTA, a = 12.353(1) $\AA$) was determined at 294 K by single-crystal X-ray diffraction in the space group Pm3 m. It was refined with all measured reflections to the final error index $R_1$ = 0.062 for 623 reflections which $F_o$ > 4$\sigma$($F_o$). 4.67 $Pb ^{2+}$ and six $K^+$ ions per unit cell are found at three crystallographically distinct positions: 3.67 $Pb ^{2+}$ and three $K^+$ ions on the 3-fold axes opposite six-rings in the large cavity, three $K^+$ ions off the plane of the eight-rings, and the remaining one $Pb ^{2+}$ ion lies opposite four-ring in the large cavity. 0.67 $Pb ^{2+}$ ions and 1.34 $I^-$ ions per unit cell are found in the sodalite units, indicating the formation of a $PbI _2$ molecule in 67% of the sodalite units. Each $PbI _2$ (Pb-I = 3.392(7) $\AA$) is held in place by the coordination of its one $Pb ^{2+}$ ion to the zeolite framework (a $Pb ^{2+}$ cation is 0.74 $\AA$ from a six-ring oxygens) and by the coordination of its two $I^-$ ions to $K^+$ ions through six-rings (I-K = 3.63(4) $\AA$). Two additional $I^-$ ions per unit cell are found opposite a four-ring in the large cavity and form $Pb _2K_2I^{5+}$ and $Pb _2K_2I^{3+}$ moieties, respectively, and two water molecules per unit cell are also found on the 3-fold axes in the large cavity.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.378-381
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• 2015

To produce low cost and efficient photovoltaic cells, inorganic-organic lead halide perovskite materials appear promising for most suitable solar cells owing to their high power conversion efficiency. Most recent research showes that formamidinium lead iodide ($FAPbI_3$) with methylammonium lead bromide ($MAPbBr_3$) improves the power conversion efficiency of the solar cell to more than 18 per cent under a standard illumination because incorporated $MAPbBr_3$ makes $FAPbI_3$-relatively unstable but comparatively narrow band gap-more stable composition. In respect to first principle study, we investigated band gap of $MAPbI_3$, $FAPbI_3$, $MAPbBr_3$, $(FAPbI_3)_{0.89}-(MAPbBr_3)_{0.11}$ and 0.615(eV), 0.466, 1.197, 0.518 respectively through EDISON DFT software. These results emphasize enhancing structure stability is important factor as well as finding narrow band gap.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.192-193
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• 2006

The wet coating process could easily be made from large area film with printing paste mixed with semiconductor and binder material at room temperature. Semiconductor film fabricated about 25mm thickness was evaluated by field emissions-canning electron microscopy (FE-SEM). X-ray performance data such as dark current, sensitivity and signal to noise ratio (SNR) were evaluated. The $Hgl_2$ semiconductor was shown in much lower dark current than the others, but the best sensitivity. In this paper, reactivity and combination character of semiconductor and binder material that affect electrical and X-ray detection properties would prove out though experimental results.

• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.789-794
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• 2021

Brachytherapy is a treatment in which radioactive isotopes are placed inside the body to intensively irradiate the tumor with radiation. Because brachytherapy uses a radioisotope source with a high dose rate, it is very important to know the exact location and dose of the source. However, in clinical practice, it is evaluated inaccurately with the naked eye through rulers and autoradiographs. Therefore, in this study, a dosimeter that can be used for brachytherapy was developed using a lead(II) iodide (PbI₂) material, and the applicability was evaluated by analyzing the reproducibility, linearity, and PID items. As a result of reproducibility evaluation, the RSD value was 1.41%, satisfying the evaluation criteria of 1.5%. As a result of the linearity evaluation, the R² value was 0.9993, which satisfies the evaluation criterion of 0.9990. As a result of PID evaluation, it showed only a difference of 0.06 cm compared with the theoretical value of the inverse square law of distance at the 50% dose reduction point. The dosimeter manufactured in this experiment shows results that satisfy the standard in all evaluations, so it is judged that the possibility of applying the dosimeter in the radiation brachytherapy area is sufficient.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.333-338
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• 2019

In the field of radiotherapy, the Quality Assurance(QA) procedure to verify the safety of treatment is considered to be very important. However, due to various problems of the conventional dosimeters used for the QA, researches on these dosimeters have been actively carried out to replace them. In this study, to maximize the sensitivity by visible light(VL) emitted from phosphors, blended hybrid sensors were fabricated by blending various weight percent(wt%) of $Gd_2O_2S:Tb$ which is a phosphor with excellent fluorescence efficiency into $PbI_2$. Then, the electrical properties to high energy radiation from the blended sensors and the pure $PbI_2$ sensor were compared and evaluated. As a result of the sensitivity evaluation, the sensor of 3wt% showed the highest value with more than 40% difference from the other sensors, and gradual decreasing in sensitivity was observed with increasing wt% except for the sensor of 3wt%. Also, in the reproducibility evaluation, the pure $PbI_2$ sensor exhibited a large variation in coefficient of variation(CV)>0.015, while all the blended sensors showed CV<0.015.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.517-522
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• 2020

Electron beam have many factors that affect dose distribution, so even if identical settings are used, they should be identified and used for radiation treatment, and the effects on the structures in the body are sensitive, making it difficult to investigate uniform dose distribution on tumors. In this study, a dosimeter was produced using PbI₂ which is a photoelectric material, and electrical characteristics were analyzed for 6, 9, and 12 MeV electronics in linear accelerators. The reproducibility test results showed that RSD were 1.1215%, 1.0160%, and 0.05137% respectively at 6, 9, and 12 MeV energies, indicating that the output signals were stable. The linearity evaluation results showed that the R² values of the reliability indicator for straight line trend lines were 0.9999, 0.9999, and 0.9994, respectively, at 6, 9, and 12 MeV, to confirm that the output signal was proportional to PbI₂ as dose increased. The PbI₂ dosimeter in this study is judged to be highly applicable to electromagnet measurement and is thought to be able to be used as a basic study of electron detector through photoelectric material.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.381-386
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• 2022

Non-Destruction Test (NDT) is a method to check internal defects without destroying the product. Among them, radiographic testing (RT) uses high-energy radiation, so it is very important to prevent radiation exposure of workers. Therefore, in this study, in this study, a radiation sensor structure that improves radiation detection performance compared to the existing PbI₂ and can immediately detect accidents in RT was presented. For evaluation, the conversion efficiency was analyzed in the gamma ray source through FLUKA simulation. PbI₂ with overlapping Gd₂O₂S:Tb presented in this study showed a higher radiation sensitivity from 1.22 to 3.22 times than that of non-overlapping PbI₂. This indicates that the presented sensor is suitable for use as a radiation sensor for source detection in RT.