Synthesis of Cu₂ZnSnS₄ Thin Films by a Precursor Solution Paste for Thin Film Solar Cell Applications

Cu₂ZnSnS₄ (CZTS) is a very promising semiconductor material when used for the absorber layer of thin film solar cells because it consists of only abundant and inexpensive elements. In addition, a low-cost solution process is applicable to the preparation of CZTS absorber films, which reduces the cost when this film is used for the production of thin film solar cells. To fabricate solution-processed CZTS thin film using an easily scalable and relatively safe method, we suggest a precursor solution paste coating method with a two-step heating process (oxidation and sulfurization). The synthesized CZTS film was observed to be composed of grains of a size of ∼300 nm, showing an overall densely packed morphology with some pores and voids. A solar cell device with this film as an absorber layer showed the highest efficiency of 3.02% with an open circuit voltage of 556 mV, a short current density of 13.5 mA/cm², and a fill factor of 40.3%. We also noted the existence of Cd moieties and an inhomogeneous Zn distribution in the CZTS film, which may have been triggered by the presence of pores and voids in the CZTS film

Bulk Heterojunction Formation between Indium Tin Oxide Nanorods and CuInS₂ Nanoparticles for Inorganic Thin Film Solar Cell Applications

In this study, we developed a novel inorganic thin film solar cell configuration in which bulk heterojunction was formed between indium tin oxide (ITO) nanorods and CuInS₂ (CIS). Specifically, ITO nanorods were first synthesized by the radio frequency magnetron sputtering deposition method followed by deposition of a dense TiO₂ layer and CdS buffer layer using atomic layer deposition and chemical bath deposition method, respectively. The spatial region between the nanorods was then filled with CIS nanoparticle ink, which was presynthesized using the colloidal synthetic method. We observed that complete gap filling was achieved to form bulk heterojunction between the inorganic phases. As a proof-of-concept, solar cell devices were fabricated by depositing an Au electrode on top of the CIS layer, which exhibited the best photovoltaic response with a <i>V</i>_oc, <i>J</i>_sc, FF, and efficiency of 0.287 V, 9.63 mA/cm², 0.364, and 1.01%, respectively

Cocktails of Paste Coatings for Performance Enhancement of CuInGaS₂ Thin-Film Solar Cells

To fabricate low-cost and printable wide-bandgap CuIn_<i>x</i>Ga_1–<i>x</i>S₂ (CIGS) thin-film solar cells, a method based on a precursor solution was developed. In particular, under this method, multiple coatings with two pastes with different properties (e.g., viscosity) because of the different binder materials added were applied. Paste A could form a thin, dense layer enabling a high-efficiency solar cell but required several coating and drying cycles for the desired film thickness. On the other hand, paste B could easily form one-micrometer-thick films by means of a one-time spin-coating process but the porous microstructure limited the solar cell performance. Three different configurations of the CIGS films (A + B, B + A, and A + B + A) were realized by multiple coatings with the two pastes to find the optimal stacking configuration for a combination of the advantages of each paste. Solar cell devices using these films showed a notable difference in their photovoltaic characteristics. The bottom dense layer increased the minority carrier diffusion length and enhanced the short-circuit current. The top dense layer could suppress interface recombination but exhibited a low optical absorption, thereby decreasing the photocurrent. As a result, the A + B configuration could be suggested as a desirable simple stacking structure. The solar cell with A + B coating showed a highly improved efficiency (4.66%) compared to the cell with a film prepared by paste B only (2.90%), achieved by simple insertion of a single thin (200 nm), dense layer between the Mo back contact and a thick porous CIGS layer

Time-course effects of 1-methoxyoctadecan-1-ol on calpain activation, STEP cleavage, and p38 MAPK phosphorylation after glutamate exposure.

<p>Cortical neurons were treated with glutamate (300 µM, 15 min) (A and C) and pretreatment with 1-methoxyoctadecan-1-ol (0.1 µg/ml, 24 h) followed by exposure to glutamate (B and D) and both were maintained in the original medium for the specified time. Equal amounts of proteins and each sample were subjected to Western blot assays using the indicated antibodies. Equal protein loading was confirmed by actin expression.</p

Effects of 1-methoxyoctadecan-1-ol on infarct volume, neurological evaluation, and wire-grip test in a photothrombotic ischemic model.

<p>Mice received intraperitoneal administration of DMSO or 1, 3/kg of 1-methoxyoctadecan-1-ol at 30 min before the ischemic insult. Representative photographs of coronal brain sections stained with TTC in vehicle (Veh)- and 1-methoxyoctadecan-1-ol-treated mice (A). White indicates the infarct area. Quantification of the infarct volume, neurological score, and wire-grip test (B). *<i>P</i><0.05, **<i>P</i><0.01 <i>vs</i>. vehicle group. Data are expressed as mean±SEM of three separate experiments.</p

Effects of 1-methoxyoctadecan-1-ol on calpain activation, STEP cleavage and p38 MAPK phosphorylation.

<p>The significant calpain1 activation (A), STEP cleavage (B) and p38 MAPK phosphorylation (C) were shown in the ipsilateral (Ipsil) cerebral hemisphere of photothrombotic ischemic mice compared with the contralateral (Con). **<i>P</i><0.01, ***<i>P</i><0.001, <i>vs</i>. vehicle group, Data are expressed as mean±SEM of three separate experiments.</p

¹H (500 MHz in CDCl₃), ¹³C NMR (125 MHz in CDCl₃) data and key HMBC correlations of 1-methoxyoctadecan-1-ol.

<p>¹H (500 MHz in CDCl₃), ¹³C NMR (125 MHz in CDCl₃) data and key HMBC correlations of 1-methoxyoctadecan-1-ol.</p

Time-course effects of 1-methoxyoctadecan-1-ol on NMDAR and AMPAR subunit after glutamate exposure.

<p>Cortical neurons were treated with glutamate (300 µM, 15 min) (A) and pretreatment with 1-methoxyoctadecan-1-ol (0.1 µg/ml, 24 h) followed by exposure to glutamate (B), then both were maintained in the original medium for the specified time. Densitometric analysis (C) showed that 1-methoxyoctadecan-1-ol treatment significantly decreased the phosphorylation of the NMDAR pGluN2B subunit. Equal amounts of proteins in each sample were subjected to Western blot assays using the indicated antibodies. Equal protein loading was confirmed by actin expression. ^#<i>P</i><0.05 <i>vs</i>. control; **<i>P</i><0.01 and ***<i>P</i><0.001 <i>vs</i>. treatment with glutamate alone. Data are represented as the mean±SEM of three independent experiments.</p

Flow cytometry analysis for neuronal death.

<p>Cortical neurons were pretreated with 1-methoxyoctadecan-1-ol (0.01 and 0.1 µg/ml) for 24 h, followed by exposure to 200 µM glutamate for 6 h. Cells were harvested and stained with Annexin V-FITC/PI, as described under methods and analyzed using flow cytometry. Annexin V⁺PI⁻ cells indicate early apoptotic cells, whereas Annexin V⁺PI⁺ cells are late apoptotic cells. The estimates (%) of gated cells in different compartments are given for each dot blot. Representative flow cytometry analysis scatter-grams of Annexin V/PI staining (A) and quantitative analysis of the histograms (B and C).^#<i>P</i><0.05 and ^##<i>P</i><0.01 <i>vs</i>. control; *<i>P</i><0.05 <i>vs</i>. treatment with glutamate alone. Data are represented as the mean±SEM of three independent experiments.</p

Effects of 1-methoxyoctadecan-1-ol on glutamate-induced apoptosis in cultured cortical neurons.

<p>Cortical neurons were pretreated with 1-methoxyoctadecan-1-ol (0.01 and 0.1 µg/ml) for 24 h, followed by exposure to 200 µM glutamate for 6 h. Quantitative analysis of the histograms for Hoechst 33342 (A) and TUNEL staining (B). ^#<i>P</i><0.05 and ^##<i>P</i><0.01 <i>vs</i>. control; *<i>P</i><0.05, **<i>P</i><0.01 <i>vs</i>. treatment with glutamate alone. Data are represented as the mean±SEM of three independent experiments.</p