• Advances in nano research
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• v.13 no.2
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• pp.187-197
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• 2022

The synthesis of organic and hybrid organic-inorganic perovskites directly from solution improves the cost- and energy-efficiency of processing. To date, numerous research efforts have been devoted to investigating the influence of the various solvent parameters for the synthesis of lead halide perovskites, focused on the effects of different single solvents on the efficiency of the resulting perovskites. In this work, we investigated the effect of solvent blends for the first time on the structure and phase of perovskites produced via the Lewis base vapor diffusion method to develop a new synthetic approach for water-stable CsPbBr₃ particles with nanometer-sized dimensions. Solvent blends prepared with DMF and water-miscible solvents with different Gutmann's donor numbers (D_N) affect the Pb ions differently, resulting in a variety of lead bromide species with various colors. The use of a DMF/isopropanol solvent mixture was found to induce the formation of the Ruddlesden-Popper perovskite based on lead bromide. This perovskite undergoes a blue color shift in the solvated state owing to the separation of nanoplatelets. In contrast, the replacement of isopropanol with DMSO, which has a high DN, induces the formation of spherical CsPbBr₃ perovskite nanoparticles that exhibit green emission. Finally, the integration of acetone in the solvent system leads to the formation of lead bromide complexes with a yellow-orange color and the perovskite CsPbBr₃.

• Current Photovoltaic Research
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• v.10 no.2
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• pp.49-55
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• 2022

With rapid growth in light-harvesting efficiency from 3.8 to 25.8%, organic-inorganic hybrid perovskite solar cells (PSCs) have attracted great attention as promising photovoltaic devices. However, despite of their outstanding performance, the commercialization of PSCs has been suffered from severe stability issues, especially for UV and humidity: (i) UV irradiation towards PSCs is able to lead UV-induced decomposition of perovskite films or catalytic reactions of charge-transporting layers, and (ii) exposure to surrounding humidity causes irreversible hydration of perovskite layers by the penetration of water molecules, resulting considerable decrease in their power-conversion efficiency (PCE). This review investigates current status of strategies to enhance UV and humidity stability of PSCs in terms of UV-management and moisture protection, respectively. Furthermore, the multifunctional approach to increase long-term stability as well as performance is discussed as advanced research directions for the commercialization of PSCs.

• 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.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.918-925
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• 2021

The perovskite solar cell is a next-generation solar cell that replaces the existing silicon solar cell. It is a solar cell device using an organic-inorganic hybrid material having a perovskite structure as a photoactive layer. It has advantages for the process and has shown rapid efficiency improvement over the past decade. In the process of commercialization of such perovskite solar cells, research and development for a large-area coating method should be carried out. As one of the large-area perovskite solar cell large-area coating methods, the slot-die coating method was studied. By using a meniscus to pass over the substrate and coating the solution, the 3D printer was equipped with a meniscus so that it could be coated. Variables that act during coating include bed temperature, coating speed, N₂ blowing interval, N₂ blowing height, N₂ blowing intensity, etc. By controlling these, the perovskite absorption layer was manufactured and the coating conditions for manufacturing large-area devices were optimized.

• 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 Convergence for Information Technology
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• v.11 no.2
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• pp.10-15
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• 2021

In this paper, we formed perovskite (CH3NH3PbI3) thin films on glass with wet coating methods, and used various analytical techniques to discuss film thickness, surface roughness, crystallinity, composition, and optical property. The coated semiconductor material has no defects and is uniform, the surface roughness value is very small, and a high absorption rate has been observed in the visible light area. Next, in order to implement the hole shape in the organic-inorganic layer, Samples in the order of a metal mask with holes at regular intervals, a glass coated with a perovskite material, and a magnet were etched with atmospheric pressure plasma equipment. The shape of the hole formed in the perovskite material was analyzed by changing the time. It can be seen that more etching is performed as the time increases. The sample with the longest processing time was examined in more detail, and it was classified into 7 regions by the difference according to the location of the plasma.

• Journal of Convergence for Information Technology
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• v.11 no.6
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• pp.146-153
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• 2021

Recently, research on perovskite semiconductor materials has been performed, and the evaluation of properties using surface treatment for this material is the basis for subsequent studies. We studied the results of surface treatment of perovskite thin films exposed to air for about 6 months by generating oxygen plasma with an atmospheric pressure plasma equipment. The reason for exposure for 6 months is that the perovskite thin film is made of organic and inorganic substances, so when exposed to air, the surface changes through reaction with oxygen or water vapor. Therefore, this change is to investigate whether it is possible to restore the original film. The surface shape and the ratio of elements were analyzed by varying the process time from 1 s to 1200 s in an oxygen plasma atmosphere. It was found that the crystal grains change over a process time of 5 s or more. In order to maintain the properties of the deposited film, it is the optimal process condition between 2 s and 5 s.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.371-377
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• 2019

A flexible piezoelectric energy harvester(f-PEH) that converts tiny mechanical and vibrational energy resources into electric signals without any restraints is drawing attention as a self-powered source to operate flexible electronic systems. In particular, the nanocomposites-based f-PEHs fabricated by a simple and low-cost spin-coating method show a mechanically stable and high output performance compared to only piezoelectric polymers or perovskite thin films. Here, the non-piezoelectric polymer matrix of the nanocomposite-based f-PEH is replaced by a P(VDF-TrFE) piezoelectric polymer to improve the output performance generated from the f-PEH. The piezoelectric hybrid nanocomposite is produced by distributing the perovskite PZT nanoparticles inside the piezoelectric elastomer; subsequently, the piezoelectric hybrid material is spin-coated onto a thin metal substrate to achieve a nanocomposite-based f-PEH. A fabricated energy device after a two-step poling process shows a maximum output voltage of 9.4 V and a current of 160 nA under repeated mechanical bending. Finite element analysis(FEA) simulation results support the experimental results.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.90-95
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• 2019

Methylammonium lead bromide ($MAPbBr_3$) has attracted a lot of attention due to their excellent optoelectronic properties such as the compositional flexibility relevant to photoluminescence (PL) and UV-Vis absorbance spectrum, high diffusion length, and photoluminescence quantum yield (PLQY). Despite such advantages of organic-inorganic perovskite materials, more systematic study on manipulation of their optoelectronic properties in homo- or heterovalent metal ions doped halide perovskite nanocrystals is lacking. In this study, we systematically investigated the optical properties of colloidal $CH_3NH_3Pb_{1-x}Sn_xCl_{2x}Br_{3-2x}$ particles by addition of $SnCl_2$ into the typical methylammonium lead tribromide ($CH_3NH_3PbBr_3$) precursor solution. We found that only 1% addition of $SnCl_2$ shows a significant blue-shift from 540 nm to 420 nm in UV-Vis absorbance spectrum due to the strong quantum confinement effect. Furthermore, continuous blue-shift in photoluminescence spectra was observed as the amount of Cl increases. These experimental results provide new insights into the replacement of Pb within $MAPbBr_3$, required for the broadening of their application.

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.332-334
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• 1992

An accurate method of density measurement is proposed. The method makes use of a gravimetric adsorption apparatus and is quite suitable for powdery and porous solid samples. The sample volume is determined by measuring its buoyancy with microbalance and the mass is measured in vacuum in the absence of buoyancy effect. Densities of inorganic compounds, such as alumina and perovskite, and some organic compounds are determined with the proposed method, and the results are compared with the values either determined with conventional methods or obtained from literatures.