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Preparation and Characterization of Thin Film Polycrystalline Solar Cells

Thesis Info

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Author

Zia, Rehana

Program

PhD

Institute

Lahore College for Women University

City

Lahore

Province

Punjab

Country

Pakistan

Thesis Completing Year

2009

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/3633

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726992100

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This thesis describes the development and characterization of single crystal and polycrystalline CdTe/ZnxCd1-xS based solar cells along with the modeling of CdTe based solar cells. Solar cells hold great hopes for use as an environmental friendly and economically viable renewable energy source. For this purpose thin film materials are being investigated by various research organizations and groups. In this work we have developed ZnxCd1-xS thin film as window layer, CdTe as absorber and ZnTe thin film to solve the back contact problem of CdTe (due to high work function) and studied their optical, electrical and structural properties. The polycrystalline layers of ZnxCd1-xS, ZnTe and CdTe solar cell in both “Superstrate” and “Substrate” configurations were developed. I-V characterization for single crystal CdTe based solar cells at different illumination levels and temperatures were carried out, which showed 14.37% efficiency. We have applied 1-D modeling to these cells to improve the efficiency at lower illumination levels. All thin film ZnxCd1-xS/CdTe solar cell showed low efficiency (1.7%) which was improved up to 3.7% by annealing the cell at 200oC for three hours.
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16 سوچن دیاںگلاں

سوچن دیاں گلاں

 

                سجنو تے مترو اک واری اک وڈھی عمر دا بندہ کسے راہ توں لنگھ رہیا سی۔ اوہدا لک جھک کے کمان وانگوں کبا ہو گیا سی۔ کسے اتھرے جوان نے بابے دے نال ٹھٹھا کردیاں آکھیا۔ بابا اے کمان کتھوں لئی جے تے کنے پیسے دتے سن۔ بابے نے منڈے دی گل نوں بڑے پیار نال جواب دے کے ٹال دتا۔ بابے نے آکھیا بچیا ایہہ کمان وقت دیندا اے تے ایسی دی قیمت صرف ذمہ داری اے۔ جیہڑی رسید بن کے باقی دی حیاتی نال جڑ جاندی اے مقصد ایہہ کہ تھوڑی دیر دے ای بعد ایہہ کمان تینوں وی پیسیاں توں بغیر ای لبھ جاوے گی۔

                ویرو تے بھراؤ کدی کسے دے نال اوہ ٹھٹھانہ کرے۔ جہدے نال اوہدے دل دا شیشہ ٹٹ جاوے۔ تے ناں کدی اپنے توں امیر نوں ویکھ کے تے سڑجایئے کہ اوہ حسد بن جاوے۔ تے ساڈے ستھرے عملاں نوں وی تباہ کردیوے۔

                اج دا زمانہ سائنس تے کمپیوٹر دا زمانہ اے۔ اہدے وچ انسان دی قیمت پاکستان روپیہ وانگوں گھٹ ہوگئی اے۔ جتھے زمینداراکرن لگیاں اک بندہ ہل چلاؤن لئی تے دوجا سہاگے لئی تے تیسرا بندہ ایہناں ساریاں بندیاں تے ڈنگراں دی خوراک لئی لوڑی دا سی۔ اوتھے ہن اک بندہ اپنے گھر وچوں کھانا کھاکے تسلی نال کھیتاں وچ جاندا اے تے ٹریکٹر نال اک گھنٹے وچ اگے نالوں ودھ کم کرکے پچھے مڑ آندا اے۔

                رب نے ایہہ ساریاں چیزاں انسان دے فائدے لئی بنائیاں نیں۔ پر حضرت انسان اوہناں چیزاں نال بڑا غلط ورتارا کردا اے بجلی نوں لے لو ایہہ تے بنی پئی گھراں وچ چانن کرے گی کارخانے ترقی کرن گے تے ساڈی سوچ وچار اگے...

External and Internal Factors of Political-Religious Violence and Pakistan’s Role: Unravel Threats for the Security of Modern Islamic State

Political scientists and Islamic philosophers have long been discussing the different phenomena of violence. This article analyzes external and internal factor of violence in Pakistan, interpreting the religious and political dimension of the violence. The presence of external and more specifically internal factors are the real threats for the security of the country. Building from theoretical approaches, I fielded two dimensions of the political-religious violence, violence inside the country and outside the country. It is found out, on the one hand, that the both dimensions can be met with the profound enforcement of the law. On the other hand, both dimensions of the violence can be the big contributory factors of violence due to the poor promulgation of the law. Unjust political-religious dispensation inside the country rise the frustration, and outside support make it fertile and leads it towards violence. It is proposed that on equity bases, political-religious deprivation and absolute deprivation of the minority elite class can be disposed of. I also come up with balanced educational system, which should be the blend of traditionalism and modernism for the fulfilment of our spiritual dimension and for the greater understanding of our political-religious outlook.

Comparative Studies on Recombinant Laccases of Thermiphilic Geobacillus Sbs-4S and Mesophilic Bacillus Strain R5 Origins

Laccases are multidomain copper containing proteins acting on phenolic and non-phenolic compounds. They are industrially relevant enzymes performing diverse oxidative functions including dye decolorization, food processing, organic synthesis and bio-remediation. Laccases exist in all domains of life. Laccases from fungal species are well characterized for industrial utilization. However, Laccases from bacterial genera are comparatively less characterized. In comparison with fungal laccases bacterial laccases are heat stable and halide tolerant, the properties desired for industrial applications. The present study describes the identification, cloning, gene expression and characterization of laccases from two sources (i) from thermophilic Geobacillus thermopakistaniensis and (ii) from mesophilic Bacillus subtilis strain R5. Genome search of Geobacillus thermopakistaniensis, formerly Geobacillus sp. SBS-4S, revealed the presence of an open reading frame (GenBank accession number ESU71923) annotated as laccase, (named as Gt-Lac). Gt-Lac gene was having 825 nucleotides, encoding a protein of 273 amino acids. The BLAST search showed that Gt-Lac does not display sequence similarity with characterized laccases of Bacillus subtilis, Streptomyces coelicolor and Thermus thermophilus. Gt-Lac shared highest homology with laccases of a new protein family, DUF152, like Kurthia huakuii (32%), RL5 laccase from bovine rumen metagenome (31%), and Thermobifida fusca (28%). To examine the properties of ESU71923, Gt-Lac was cloned in expression vector (pET-21a) and mobilized to E. coli for the production of recombinant enzyme. However, the purified recombinant protein did not exhibit any laccase-like activity even when produced in the presence of copper ions. Expression of Gt-Lac gene at low temperatures and in the presence of zinc also failed to produce an active enzyme. Atomic absorption spectroscopy could detect only zinc atom instead of four coppers that most laccases possess. Based on these results it was suggested that ESU71923 does not encode a functional laccase. The laccase activity was, therefore, purified from G. thermopakistaniensis cells and N-terminal amino acid residues of the enzyme were determined. These residues matched the N-terminal sequence of an open reading frame annotated as a copper oxidase (ESU72270). In order to characterize the enzyme, recombinant ESU72270 (named as Gt-Cuo) was prepared in Escherichia coli. Gt-Cuo gene encoded a protein of 503 amino acids with a molecular weight of about 60 kDa. The recombinant protein was found to exhibit a negligible amount of laccase activity when produced in the absence of copper in the growth medium. However, the recombinant protein exhibited significantly high laccase activity when produced in the presence of copper. The recombinant enzyme showed highest activity at 60 °C and a pH of 7–7.5. Gt-Cuo was copper dependent and a five-fold increase in laccase activity was observed in the presence of 100 μM copper sulfate. When using halide donors, a 7-fold and 5-fold increase in laccase activity was observed with 500 mM NaBr and NaCl, respectively. Gt-Cuo showed good stability towards organic solvents. Moreover Gt-Cuo was able to decolorize several synthetic dyes with highest rate of color removal observed for indigo caramine. In conclusion, this is the first report about the identification of gene, from genus Geobacillus, responsible for true laccase activity having potential to be used for biotechnological applications. The third gene of the study, (named as Bsu-Lac) laccase from Bacillus subtilis was composed of 513 amino acids with calculated molecular weight of 58498.99 Da. When expressed in E. coli the recombinant Bsu-Lac was produced as inclusion bodies which were tried to refold by denaturing in urea but the refolded sample was inactive. Co-expression of Bsu-Lac gene with a chaperonin gene also failed to solubilize the inclusion bodies. Finally expression of Bsu-Lac gene was taken in pET-28a(+) at low temperature and the protein was purified by nickel affinity chromatography. The enzyme was found to function optimally at 55 °C and a pH of 7. The laccase activity of Bsu-Lac was dependant on copper only during protein production rather than adding in assay mixture, showing the importance of copper for proper protein folding. The enzyme was stable in 10% of all tested organic solvents. The Bsu-Lac activity was stable at 80 °C for 150 min. When the protein was incubated with various concentrations of urea, structural stability was found even at 8 M urea. The recombinant protein was able to degrade various synthetic dyes with the highest rate of dye degradation for orange G, thus having potential for various industrial applications.