109 research outputs found
Effect of Sn/Zn/Cu precursor stack thickness on two-step processed kesterite solar cells
No full textWe have fabricated Cu2ZnSnSe4 (CZTSe) solar cells with different absorber layer thickness. Absorber layers with different thicknesses were fabricated by changing the thickness of e-beam evaporated Sn/Zn/Cu precursor stacks and then selenization in a rapid thermal processing system. Scanning electron microscopy revealed that by increasing the thickness the morphology of CZTSe films improves substantially and energy dispersive spectrometry measurements showed that the Cu to Sn ratio increased with increasing the film thickness, despite a similar Cu to Sn ratio in the starting layers. A longer minority carrier lifetime and higher open circuit voltage were achieved for solar cells with thicker absorber layers. A maximum conversion efficiency of 7.8% (without anti reflection coating) was achieved for a solar cell with 1.7 mu m thickness in which a low doping density of the order of 10(15) cm(-3) was measured, leading to a wide space charge region of about 300 nm. (C) 2016 Elsevier B.V. All rights reserved.This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 640868. This research is partially funded by the Flemish government, Department Economy, Science and innovation. This work is also funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the project UID/CTM/50025/2013. Samaneh Ranjbar acknowledges the financial support of the Portuguese Science and Technology Foundation (FCT) through PhD grant SFRH/BD/78409/2011. B. Vermang acknowledges the financial support of the Flemish Research Foundation FWO (mandate 1204215N)
Alkanna semiromica Ranjbar & Khalvati 2021, sp. nov.
No full text2. Alkanna semiromica Ranjbar & Khalvati, sp. nov. Fig. 10. Type: — IRAN. Isfahan: Semirom, 31°25’ 0.01”N, 51°34’0.01”E, 2950 m, 30 April 2012, Ranjbar 30880 (holotype BASU!). Fig. 11. Diagnosis: —The new species is similar to Huynhia pulchra, but differs by its smaller cauline leaves (1.2–2 cm versus 3–5 cm), pedicel in fruiting state (up to 8 mm versus up to 5 mm), blue to light violet corolla (versus sulphur yellow with purple spots), shorter corolla (12–14 mm versus 18–20 mm), calyx in flowering state (7–10 mm versus 8–14 mm), shorter style 5–7 mm (versus 9–10 mm) and stigma shallowly bilobed (versus deeply bilobed). The pollen grains are ovoid and 3-colporate, in contrast to prolate and stephanocolporate pollen in H. pulchra. Pollen characters fit Alkanna, in where the new species is similar to but differs from A. frigida. It differs by corolla dark blue (versus sulphur yellow), shorter basal leaves (8–15 × 0.5–1 mm versus 30–100 × 5–12 mm) and narrow corolla limbs (versus broad limbs). Etymology: —The specific epithet refers to Semirom, a city in Isfahan province, where the new species was found. Description: —Perennial green plant, with stout scaly stock. Stem multi-branched, branched from base, densely patent-pilose. Basal leaves, oblong to ovate, 8–15 × 0.5–1 cm, acute to subacute, tapering into the petiole, with entire, flat, or sometimes slightly undulate margins, white setose, sometimes with prominent base. Cauline leaves, oblong to lanceolate, 1.2–2 × 0.3–0.5 mm, acute or subacute, sessile, attenuate at base, with an evident midrib, veinless, densely white setose. Inflorescence a compact terminal head; 2–3 × 1.5–3 cm, pedicels short, leafy, peduncle 1–2 cm long; bracts oblong to ovate, 12–15 × 3–5 mm. Calyx 7–10 mm long in flower, up to 15 mm long in the fruiting state, broad at nearly the base; lobes linear to lanceolate, acute, densely hispid-setose with yellowish, patent setae up to 2 mm long. Corolla blue to violet light, lobes 12–14 mm long, loosely pubescent outside, slightly pilose inside, slightly constricted below the anthers. Annulus absent. Stamens inserted irregularly at different levels; three higher at the throat and two lower down in the middle of the tube. Anthers 1.5–2 mm long. Style 5–7 mm long, reaching up to the middle of the corolla tube, shallowly bilobed; lobes 0.2 mm long. Nutlet not seen. Palynology: —Pollen grains heteropolar, triangular concave, tricolporate, equatorial axis (E) 9.3 ± 1.9 μm, polar axis (P) 11.5 ± 3.85 μm, ornamentation psilate. Fig. 5. Distribution and ecology: — Alkanna semiromica was seen in the field by the first author and is known from a single specimen from the type locality that is deposited at the herbarium of Bu-Ali Sina University (BASU). The new species occurs in Isfahan province. It is endemic to southwestern Iran and known only from the type locality. It was collected from the rocky terrain along the roadside of the Black Mountains. IUCN Red List category: —A low frequency of the new species in one field locality was observed and therefore decided to classify this species as VU (Vulnerable). This category includes taxa with small populations that could be at risk, according to IUCN criteria (IUCN, 2001). We revisited the locality, where the new species was discovered and the neighboring areas in 2019. Our interpretation is based on a single known population. Pollen morphology: —Members of the family Boraginaceae represent a great array of pollen types, and thus the family is interesting for investigating the evolution of pollen characters (Noroozi et al 2021). Pollen characters can provide other elements with taxonomic significance can play important role in diversification of the group. According to previous studies, the pollen morphology of the Huynhia has been described as radial symmetric, isopolar with prolate shapes, polycolpate types, and with psilate ornamentations (Tab. 1; Coppi et al. 2015, Khatamsaz 2001). The pollen grains of the new species were observed as triangular concave and 3-colporate, which fits the ancestral state of the Lithospermeae and is realized in the genus Alkanna (Noroozi et al. 2021). The average polar axis (P) was between 11.5–15.35 μm and the average equatorial axis (E) between 9.3–11.19 μm. From this palynological information we infer the taxonomic placement of the new species in the genus Alkanna. * p: prolate; ell: elliptical; tc: triangular concave ** Data taken or adapted from Coppi et al. 2015 (2015). Taxonomic discussion: —The specimens kept at BASU, M. Ranjbar 30880, were determined morphologically as H. pulchra (Willdenow ex Roemer & Schultes) Greuter & Burdet, which are confined to Isfahan province. Herbarium material of this species is very scarce. However, when the specimens were more thoroughly examined, several characters appeared to be dissimilar to that species and other closely related species. The new species is similar to H. pulchra, especially by its habit, indumentum, number of leaflets, and shape, size, and arrangement of pods, and also differs from H. pulchra, by pollen shape, stigma shallowly bilobed, shorter style, smaller corolla, and calyx in anthesis. General and detailed characters of the vegetative parts and flowers in Huynhia are already well known from various literature. Here, two characters are worthy of mention because of their taxonomic significance; one concerning the androecial arrangement and other the stigma structure. In Huynhia the epipetalous stamens are inserted through very short filaments at different heights within the corolla tube, e.g., three higher at the throat and two lower down in the tube, however, this character also occurs in Alkanna frigida (Khatamsaz 2002) (Fig. 12). Given the payonlogical evidence from above, the new Iranian blue to light violet-corolla species is fully described here as a new species and named as Alkanna semiromica.The differences in characters of the new species and its relatives are shown in Table 2.Published as part of Khalvati, Sina & Ranjbar, Massoud, 2021, The comparative study of Alkanna and Huynhia (Boraginaceae, Lithospermeae), with description of a new species in Iran, pp. 216-234 in Phytotaxa 524 (4) on pages 227-230, DOI: 10.11646/phytotaxa.524.4.1, http://zenodo.org/record/565635
Progress in Cleaning and Wet Processing for Kesterite Thin Film Solar Cells
No full textCopper indium gallium selenide/sulfide (CIGS) and copper zinc tin selenide/sulfide (CZTS) are two thin film photovoltaic materials with many similar properties. Therefore, three new processing steps - which are well-known to be beneficial for CIGS solar cell processing - are developed, optimized and implemented in CZTS solar cells. For all these novel processing steps an increase in minority carrier lifetime and cell conversion efficiency is measured, as compared to standard CZTS processing. The scientific explanation of these effects is very similar to its CIGS equivalent: the incorporation of alkali metals, ammonium sulfide surface cleaning, and Al2O3 surface passivation leads to electrical enhancement of the CZTS bulk, front surface and reduced front interface recombination, respectively.This work is funded by the Flemish government (Department Economy, Science and Innovation) and the European Union (Horizon 2020 grant agreement No 640868). B. Vermang acknowledges the financial support of the Flemish Research Foundation FWO (mandate 12O4215N)
Effect of the duration of a wet KCN etching step and post deposition annealing on the efficiency of Cu2ZnSnSe4 solar cells
No full textThe influence of the duration of the KCN etching step on the efficiency of Cu2ZnSnSe4 (CZTSe) solar cells and Post deposition annealing (PDA) has been explored. CZTSe thin film absorbers prepared by selenization at 450 °C were etched by 5 wt% KCN/KOH from 30s up to 360 s before solar cell processing. KCN etching times above 120 s resulted in poor efficiencies. The fill factor (FF) and short circuit current density (Jsc) of these deviceswere affected severely. After annealing the solar cells at 200 °C in N2 atmosphere the best devices degraded and poor devices
improved. Combined physical and optoelectronic characterization of the solar cells showed that PDA modifies the bulk defect density and also surface composition which reflects in the solar cell performance.sponsorship: This research is partially funded by the Flemish government Department Economy, Science and innovation. This research has received funding from the European Union's Horizon 2020 - Research and Innovation Framework Programme under grant agreement No. 640868. (Flemish government Department Economy, Science and innovation, European Union's Horizon 2020 - Research and Innovation Framework Programme|640868, H2020 Societal Challenges Programme|640868)status: Publishe
P–N Junction Passivation in Kesterite Solar Cells by Use of Solution-Processed TiO2 Layer
No full textIn this work, we used a solution-processed TiO2 layer between Cu2ZnSnSe4 and CdS buffer layer to reduce the recombination at the p-n junction. Introducing the TiO2 layer showed a positive impact on VOC but fill factor and efficiency decreased. Using a KCN treatment, we could create openings in the TiO2 layer, as confirmed by transmission electron microscopy measurements. Formation of these openings in the TiO2 layer led to the improvement of the short-circuit current, fill factor, and the efficiency of the modified solar cells.This work was supported in part by the European Union's Horizon 2020 research and innovation program under Grant 640868, in part by the Flemish government, Department Economy, Science and Innovation, in part by the FEDER funds through the COMPETE 2020 Programme, and in part by the National Funds through FCT - Portuguese Foundation for Science and Technology under the project UID/CTM/50025/2013. The work of S. Ranjbar was supported by the Portuguese Science and Technology Foundation through Ph.D. grant SFRH/BD/78409/2011. The work of B. Vermang was supported by the Flemish Research Foundation FWO (mandate 12O4215N). (Corresponding author: Samaneh Ranjbar.
interfacial layer
No full textIn this study, an ultra-thin MoO3 layer synthesized by a solution-based technique is introduced as a promising interfacial layer to improve the performance of kesterite Cu2ZnSnSe4 (CZTSe) solar cell. Solar cells with 10nm of MoO3 between Mo rear contact and CZTSe had larger minority carrier life time and open-circuit voltage compared to the reference solar cells. Temperature dependent current density-voltage measurement indicated that the activation energy (E-A) of the main recombination is higher (approximate to 837 meV) in solar cells with MoO3 layer, as compared to conventional solar cells where E-A approximate to 770meV, indicating reduced interface recombination. A best efficiency of 7.1% was achieved for a SLG/Mo/MoO3/CZTSe/CdS/TCO solar cell compared to the reference solar cell SLG/Mo/CZTSe/CdS/TCO for which 5.9% efficiency was achieved.This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 640868. This research is partially funded by the Flemish government, Department Economy, Science and innovation. This work is also funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the project UID/CTM/50025/2013. This work is also supported by JSPS Core-to-Core Program, A. Advanced Research Networks. S. Ranjbar acknowledges the financial support of the Portuguese Science and Technology Foundation (FCT) through PhD grant SFRH/BD/ 78409/2011. B. Vermang acknowledges the financial support of the Flemish Research Foundation FWO (mandate 12O4215N)
Modifying the split-step theta-method with harmonic-mean term for stochastic differential equations
No full text[EN] In this paper, we design a class of general split-step methods for solving Ito stochastic differential systems, in which the drift or deterministic increment function can be taken from special ordinary differential equations solver, based on the harmonic-mean. This method is justified to have a strong convergence order of 1/2. Further, we investigate mean-square stability of the proposed method for linear scalar stochastic differential equation. Finally, some examples are included to demonstrate the validity and efficiency of the introduced scheme.This research was in part supported by the Research Council of Semnan University, and in part by a grant 97007950 from Iran National Science Foundation (INSF). Also, the third author acknowledges the support by the Spanish Ministerio de Economia, Industria y Competitividad (MINECO), the Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER UE) grant MTM2017-89664-P. The authors are grateful to the anonymous reviewers for their careful reading, insightful comments and helpful suggestions which have led to improvement of the paper.Nouri, K.; Ranjbar, H.; Cortés, J. (2020). Modifying the split-step theta-method with harmonic-mean term for stochastic differential equations. International Journal of Numerical Analysis and Modeling. 17(5):662-678. https://riunet.upv.es/handle/10251/164481S66267817
Enhanced mass transfer and water discharge in a proton exchange membrane fuel cell with a raccoon channel flow field
No full textThe cathode flow channel plays an important role in the water management of proton exchange membrane (PEM) fuel cells. In order to improve mass transfer and water management in traditional channels, this paper presents a new wavy flow field to increase the fuel cell performance and overall efficiency. A raccoon channel with various waviness parameters is numerically studied by a three-dimensional two-phase PEM fuel cell model. The electrochemical current-voltage performance results confirm that the PEM fuel cell's performance with the raccoon design is higher than a conventional straight channel at high current densities. The effects of uniform gas distribution, removal of the accumulated water, and sufficient water content in the membrane are crucial factors for improving cell performance. A parametric analysis is also performed by considering the amplitude and wavelength of the raccoon pattern on the fuel cell performance. The results show that the output power improves in the raccoon channel by increasing the amplitude or increasing the wavelength. The raccoon channel's output power with amplitude of 0.5 mm and a wavelength of 2 mm is enhanced by about 20%. The increase of performance in the raccoon channel is significantly higher than in the past reported studies
Nondestructive measurement of refractive index profile of optical fiber preforms using moire technique and phase shift method
No full textEvaluation of multiple-locus variable-number tandem repeat analysis (MLVA) for genotyping of Escherichia coli isolated from Karaj River
No full textAbstract
Most microbiological water quality regulations rely upon the detection of indicators of fecal pollution, such as coliform bacteria, or more specifically Escherichia coli. In order to further understand the source, fate, and implications for water quality regulation, environmental E. coli isolates should be assessed genetically to observe various levels of genotypic diversity. Multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA) is a novel, simple and inexpensive polymerase chain reaction (PCR) based genotyping method which relies on the detection of different copy numbers inside each VNTR locus. In this study, we evaluated MLVA as a tool for the genotyping of E. coli strains of water samples collected from the Karaj River, Iran. Overall, high genetic diversity was observed among environmental E. coli isolates. We also proved the feasibility of MLVA as a complementary or even future replacement genotyping method for the average routine laboratory.</jats:p
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