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Novel Materials for Dye Sensitized Solar Cells

Thesis Info

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Author

Javed, Sofia

Program

PhD

Institute

National University of Sciences & Technology

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2015

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/6735/1/Sofia_Javed_HSR_Materials_%26_Surface_Engineering_2015_NUST_25.11.2016.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726767874

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Dye sensitized solar cells (DSSCs) being third generation photovoltaics are inexpensive renewable energy resource and recently been a hot topic of research. The objective of the present research work was to develop photoanode materials for low cost efficient DSSCs. This thesis presents some novel materials for the photoanode including semiconductor material with different nanostructures such as nanoparticles, nanoflowers and nanorods and new sensitizers. Synthesis method of titanium dioxide nanoflowers is reported here. Such hierarchical morphology led to the improved device performance due to greater absorption of light through scattering; a novel photoanode with one dimensional sandwich configuration of ZnO/Au/TiO2, incorporating plasmon resonance and charging effects of Au nanoparticles for enhanced efficiency in DSSCs. New metal free calixarene sensitizers with directed flow of electrons are also studied for DSSCs. Titania nanoflowers are highly desirable in light driven applications due to their large surface area and greater light absorption capabilities. Microwave synthesis of nanomaterials is an energy efficient and quick method. Microwave treatment of titania nanopowders under alkaline conditions is carried out to see the effect of treatment duration. An instant, simple, inexpensive and environment friendly method of preparing titanium dioxide nanoflowers or hierarchical nanostructures (HNSs) is thus achieved. Production of sub-micron sized HNSs without any surfactant or hydrofluoric acid is discovered. From FESEM and TEM analysis the titania nanoflowers are found to be made of few nanometers thick radially arranged nanosheets. XRD and Raman spectra reveal no phase change during the microwave treatment. The mechanism of formation of these hierarchical nanostructures involves sheet formation under strong alkaline conditions and their radial growth under the effect of microwave radiation. The hierarchical morphology provides huge surface area for maximum exposure for light driven reactions and 3 D folding morphology allows further scattering of light to get its maximum utilization. This is evident in improved DSSC performance with synthesized nanoflowers. The HNSs produced in a time as short as 5 minutes show improvement in DSSC efficiency by about 216%. vii One dimensional nanostructures of TiO2 and ZnO have also been vastly studied for application in DSSCs. As a novelty in configuration of 1D core/shell nanostructures, the effect of Au nanoparticles inclusion as a sandwiched layer is studied. The sputter coated gold nanolayers of various sizes are applied over ZnO nanorods grown by seed assisted route. 1D Au/ZnO nanoarrays are covered with a few nanometers thick spin coated TiO2 film to make TiO2/Au/ZnO sandwich nanorod arrays. The uniform morphology and dimensions of the nanorod arrays are studied by SEM. HRTEM studies depict the Au nanoparticle size and distribution within the sandwich nanorods and they are found to be embedded at the interface of ZnO/TiO2 coreshell nanorods. The UV/Vis spectra reveal the plasmon resonance effects due to Au nanoparticles, which are also improving the solar cell efficiencies. The observed enhancement in the photocurrent density is attributed to the Localized Surface Plasmon Resonance (LSPR) effects due to sputter coated Au layers. An increase in the open circuit voltage of DSSCs is also observed due to Fermi level alignment between the Au bridged ZnO and TiO2 in the photoanodes of devices. With 2nm sputter coated Au in TiO2/Au/ZnO 1D nanostructures, a relative efficiency enhancement factor of 2.05 is achieved. Further in search of new inexpensive materials for DSSCs, a new class of metal free Donor-π-bridge-Acceptor (D-π-A) dyes based on basket shaped molecules “calixarenes” is introduced for DSSCs. As in calixarenes the flow of electrons is directed along the length of the molecules by resonance and induction effects and there is no conjugation around the molecular cup. This fact can prevent the recombination of charge carriers to a great extent. p-(6-chloro-2- benzothiazolylazo)calix[4]arene (pcb calix) and p-(1,3,4-thiadiazol-2-thiol-5- ylazo)-calix[4]arene (ptt calix) are synthesized and after characterization by FTIR, UV/Vis, NMR spectroscopy and cyclic voltametry are employed in DSSCs to sensitize titania. The HOMO LUMO levels of the dyes are found consistent with the requirement of DSSCs. An efficiency of 0.3% and 0.47% is achieved with dyes pcb-calix and ptt-calix respectively. The attachment of better absorbing chromophores to calixarene can result in obtaining better efficiencies in DSSCs.
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, طوطے تے گالڑ دی دوستی

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اک واری دی گل اے کہ اک جنگل وچ اک طوطا رہندا سی۔ طوطا بہت خوش سی کہ اوس نوں جنگل وچوں کھاون لئی وافر پھل مل جاندے نیں۔ اوہ ایہناں نوں کھاندا تے جنگل دی سیر کردا۔ اک دن اوہ امرود دے درخت اتے بیٹھا امرود کھا رہیا سی کہ اک گالڑ وی اوس درخت اتے چڑھ آندا اے۔ پہلاں اک دوجے دے یار بن جاندے نیں۔ طوطا گالڑ نوں امرود کھواوندا اے تے اپنے گھر آون دی دعوت دیندا اے۔ ایس توں بعد طوطا تے گالڑ اپنے اپنے گھر آ جاندے نیں۔

کئی دناں توں بعد اک دن ہلکے ہلکے بدل آئے ہوئے سن۔ ٹھنڈی ہوا چل رہی سی۔ گالڑ گھر وچ ویہلا سی۔ اوس دے من وچ خیال آیا کہ کیوں نہ اج طوطے دے گھر پھیرا پایا جاوے۔ ایس خیال دے آوندیاں ای اوہ تیار ہو کے طوطے دے گھر اپڑ جاندا اے۔ طوطا اوہنوں اپنے گھر ویکھ کے بہت خوش ہوندا اے تے جی آیاں نوں آکھدا اے۔ جنگل وچوں ہر طرح دے پھل اکٹھا کر کے اوہدی مہمان نوازی کر دا اے۔ گالڑ سب کجھ کھا کے طوطے کولوں گھر واپسی دی اجازت لیندا اے۔ واپسی تے گالڑ طوطے نوں اپنے گھر آون دی دعوت دیندا اے۔ جو طوطا قبول کر لیندا اے۔

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Line Item Budgeting on Labor Costs to the Level of Income

Library research is a data collection technique through the library in the form of literature books, and lecture materials that are relevant to the problem under study. In this study, the authors used the following data collection methods Research library (library research) It is a data collection technique through the library in the form of literature books, and lecture materials that are relevant to the problem under study. Field research (field research) is direct retrieval of the object under study by taking the following steps Observation, namely data collection through direct observation of the object under study, Interviews, namely conducting interviews with leaders and parties interested in the object of research.

The Influence of Plant Spacing, Floral Buds, Seed Extraction Time on Okra Saeed Production and Retention of Quality During Storage

A series of experiments were organized to investigate the “Influence of plant spacing, floral buds, seed extraction time on okra seed production and retention of quality during storage” during the years 2012-2014 at the University of Agriculture, Peshawar. The experiment on influence of plant spacing (20, 30 and 40 cm) on the growth and seed production of five okra (Abelmoschus esculentus L. Moench) varieties i.e. Sabz Pari, Arka Anamika, Pusa Sawani, Punjab Selection and Green Star revealed that Arka Anamika variety had the maximum plant height (136.8 cm), number of branches per plant (1.42), number of pods per plant (26.33), number of seeds per pod (60.67), seed weight per pod (3.87 g) and seed yield (4.54 t ha-1). The plant spacing of 20 cm resulted in the maximum plant height (136.92 cm) but planting of okra plants at 40 cm plant spacing resulted in the maximum seeds per pod (67.28), seed weight per pod (4.61 g), 100 seed weight (6.87 g) and seed yield (4.42 t ha-1) as well as significant variations in the seed weight per pod due to varieties x spacing interaction. The study of floral buds (8, 11, 14, 17 and 20) retention on the plant growth, seed yield and quality attributes of five okra varieties i.e. Sabz Pari, Arka Anamika, Pusa Sawani, Punjab Selection and Green Star revealed significant variations in different varieties except mean hard seeds. The maximum plant height (131.65 cm), number of branches per plant (2.04), number of seeds per pod (65.30), seed weight per pod (4.29 g), seed yield (2.37 t ha-1) was observed in variety Arka Anamika. The number of leaves per plant (39.88) was the highest in Sabz Pari, while the 100 seed weight was maximum (7.55 g) in Pusa Sawani, followed by Arka Anamika (7.48 g). The number of floral buds retained for seed production also significantly influenced the vegetative growth and seed yield. The retention of 8 floral buds resulted in the maximum plant height (128.1 cm), number of branches per plant (2.16), number of seeds per pod (69.72), seed weight per pod (4.29 g), but the minimum seed yield (1.51 t ha-1). Whereas, the highest seed yield (2.77 t ha-1) and hard seed percentage (26.77%) was recorded with 20 floral buds retained for seed production. The varieties x floral buds interaction significantly affected the plant height and seed yield. The plant height was maximum (134.47 cm) in Arka Anamika with 8 floral buds retained and minimum in Sabz Pari (109.9 cm) with 20 buds retained. The maximum seed yield (3.69 t ha-1) in Arka Anamika was observed with 20 floral buds retained for seed production, whereas the minimum seed yield (1.42 t ha-1) was recorded in Punjab Selection with 8 floral buds retained for seed production. The experiment on influence of seed extraction time, packing materials and storage durations on the okra seed quality was conducted by extracting seeds of okra at 0, 15 and 30 days after pods harvesting, packed in aluminum, polythene, cloth, gunny and paper bags and stored for 0, 3, 6, and 9 months. The seed quality attributes such as seed x moisture content, percent germination, length of seedling, seedling dry weight, vigor index, electrical conductivity and hexanal production were assessed. It was observed that the seed extracted immediately (0 days) after pods harvesting had the maximum mean seed moisture content (13.38%), hexanal production (12.96 μg kg-1) and electrical conductivity (125.66 μs cm-1) but the least germination percentage (73.75%), length of (20.43 cm), dry seedling weight (17.09 mg/10 seedlings) and seedling vigor index (1521.3). By contrast extracting the seeds 30 days after pods harvest resulted in the minimum seed moisture content (11.45%), hexanal production (6.80 μg kg-1) and electrical conductivity (59.76 μs cm-1) as well as the highest germination percentage (93.58%), seedling length (30.74 cm), seedling dry weight (26.35 mg/10 seedlings) and seedling vigor index (2881). Among the packing materials, the maximum mean moisture content (12.37%) was recorded with seed stored in aluminum bags, but the maximum percent germination (88.33%), length of seedling (27.98 cm), seedling dry weight (23.94 mg) and seedling vigor index (2509.9); least hexanal production (8.69 μg kg-1) and electrical conductivity (77.13 μs cm-1) were recorded with seed packed in polythene bags. The seed quality attributes declined with increasing storage durations. The seed moisture content, germination percentage, seedling length, dry seedling weight and vigor index decreased while hexanal production and electrical conductivity increased with increasing storage duration. The experiment on the influence of packing materials and storage durations at room temperature on okra seed quality was conducted by packing the variety Arka Anamika seed in aluminum, polythene, cloth, gunny and paper bags and stored for 0, 3, 6, 9, 12, 15 and 18 month durations at room temperature. The data revealed that the packing materials and storage durations had significant effect on the seed quality attributes. Among the different packing materials, the maximum seed moisture content (10.69%), germination (89.52%), seedling length (30.18 cm), dry seedling weight (25.96 mg), seedling vigor index (2713.7) and least hexanal accumulation (18.17 μg kg-1) as well as electrical conductivity (92.23 μs cm-1) was recorded in seeds packed in cloth bags, that were at par with aluminum bags in most of the quality attributes evaluated. The data regarding seed quality attributes in relation to seed extraction time revealed that the highest seed moisture (12.89%), seedling length (33.06 cm) and seedling dry weight (28.49 mg/10 seedlings); as well as the least hexanal content (0.0 μg kg-1) and electrical conductivity (61.70 μs cm-1) were recorded in fresh seeds, while the maximum germination percentage (94%), and seedling vigor index (3055.8) were observed in seeds stored for 3 months. Beyond, 3 months storage, all the seed quality attributes decreased with concomitant increase in hexanal content and electrical conductivity. Thus, the minimum seed quality attributes such as seed moisture content (8.68%). germination (71.67%), seedling length (24.24 cm), seedling dry weight (20.37 mg) and seedling vigor index (1752.2); and the maximum hexanal accumulation (40.40 μg kg-1) and electrical conductivity (154.0 μs cm-1) were recorded after 18 months storage at room temperature. To determine the influence of packing materials, storage conditions and durations on the okra seed quality, variety Arka Anamika was packed in aluminum, paper and polythene bags and stored in cold, refrigerated and room temperatures for 0, 3, 6, 9, 12, 15 and 18 months. The data revealed that the packing materials, storage conditions and storage durations had significant effect on the seed quality. Among the different packing materials, the highest seed moisture content (12.87%) was recorded in seed stored in paper bags and maximum germination percentage (90.79%) was recorded in xi seeds stored in polythene bags. The polythene and aluminum bags had higher but at par seedling length (30.63 and 30.52 cm), dry seedling weight (26.23 and 26.09 mg), seedling vigor index (2703.8 and 2879.5) and lower hexanal content (16.47 and 77.11 μg kg-1) and electrical conductivity (86.30 and 89.22 μs cm-1) as compared to the seed stored in paper bags. The seed stored in cold storage condition had the highest seed moisture content (12.56%), germination (86.98%), seedling length (29.76 cm), seedling dry weight (25.47 mg) and vigor index (2616.8) as well as the least hexanal production (19.41 μg kg-1) and electrical conductivity (98.63 μs cm-1). The data on seed quality attributes in relation to storage durations revealed that the highest germination percentage (93.52%) and seedling vigor index (3042.6) was recorded in seed stored for 3 months. The highest seed moisture (12.91%), seedling length (33.02 cm), seedling dry weight (28.65 mg) and least hexanal content (0.00 μg kg-1) and electrical conductivity of the seed (61.29 μs cm-1) was recorded in the fresh seed. The seed storage for 18 months resulted in the minimum seed moisture (11.11%), germination percentage (72.22%), seedling length (24.48 cm), dry seedling weight (20.58 mg/10 seedlings), vigor index (1801.3) and the highest hexanal content (44.77 μg kg-1) and electrical conductivity (157.69 μs cm-1) of the okra seed." xml:lang="en_US