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Synthesis and Characterization of Thin Film Materials for Photovoltaic Applications

Thesis Info

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Author

Tariq, Ghulam Hasnain

Program

PhD

Institute

COMSATS University Islamabad

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2222/1/2771S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727466653

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The aim and objective of this work is to develop low cost, and naturally abundant semiconductor thin film materials for photovoltaic applications. In this work, different materials for window, absorbent and interfacial layers are studied. This study was done for synthesis and characterization of these thin film materials. All these materials were deposited by using thermal evaporation method. Characterization of sample material was carried out using Raman spectroscopy, X-ray diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), UV-Vis-NIR spectrophotometer and Photoconductivity. Furthermore conductivity type determination was performed by using hot probe technique. CdS thin films were deposited at chamber ambient temperature and annealing was done in vacuum at 400 ̊C for 1 hour. Further these films were doped with Al using ion exchange method. In XRD patterns no peaks of Al and Al2S3 were found, which revealed that the incorporation of Al+3 ions does not alter the crystalline structure of these doped CdS thin films. The bandgap of CdS initially decreased for Al doping and then increased with the increase in Al concentration and finally reached a saturation value of 2.42 eV for 18 at.% of Al. All Al-doped CdS thin films showed n- type conductivity. CdTe thin films for applications as absorber layer in thin film solar cells (TFSCs) were studied. These thin films were deposited by thermal evaporation and were effectively doped with Cu by using ion exchange technique. At higher annealing temperature variation was found in size of crystallites. The obtained bandgap energy values changed from 1.53eV to 1.42eV for samples annealed at 100-400°C. The type of conductivity was concluded to be p-type for all CdTe films doped with Cu. Further in this work, to discover nontoxic absorber layer material, libraries of (SnS)x-(Bi2S3)1-x graded thin films were successfully deposited by using combinatorial synthesis approach (CSA) via thermal evaporation. Effect of annealing in vacuum and elemental composition was studied. XRD studies confirmed that these thin films are grown in different binary and ternary phases and were well crystalline; also these have better surface homogeneity, crystalline and more compact morphology. Photo conductivity response showed a shift towards smaller wavelengths (blue shift) as the temperature of annealing was increased to 400°C. It was also improved progressively for atomic ratio of Sn/Bi (0.22 to 2.11). Bandgap energy increased from 1.23 eV to 1.48 eV for variation in Sn/Bi value from 0.21 to 6.67. Films having compositions Sn/Bi > 2 and annealed at 400 ̊C showed p-type conductivity and could be used as an active photon absorber layer. In the next phase, we have studied the influence of annealing temperature on Sn-Bi-S graded thin films annealed in Argon environment. The structural and morphological properties were investigated, which showed that the thin films with different well crystallized binary phases and good surface homogeneity are grown. The estimated value of bandgap was in the range 1.27-1.43eV for Sn/Bi of 2.18-0.67. Moreover, samples annealed over temperature of 400°C -500°C showed better photoconductivity response. Photoconductivity response was better for samples containing Sn rich compositions and these showed p-type conductivity over the temperature range of 350-400 ̊C. As a part of search for nontoxic photovoltaic materials, thin films of Cu-Sn-S were successfully prepared on glass slides. Further annealing of all these samples was done in vacuum at 350̊C for two and half hours. Bandgap increased (1.07 – 1.47 eV) with increase in Cu content (7-18 at.%). Photo response also improved gradually with increasing Cu at.% in these thin films. All samples showed p-type conductivity. For development of low resistance interfacial layer, ZnTe thin films were deposited on glass slides via thermal evaporation and were effectively doped with Cu using ion exchange method. Optical bandgap decreased with annealing at 300°C, which verifies the settlement of doped Cu in ZnTe thin films. The resistivity of as doped sample was 148 Ω-cm and after annealing at 400°C for one hour it was reduced to 30 Ω-cm. The conductivity type of these Cu doped ZnTe thin films was observed to be p-type. These conclusions can help out in manufacturing of CdTe TFSCs. Our obtained results for Al doped CdS thin films with improved bandgap energy of 2.42eV are useful for utilization of these materials as window layer in different types of TFSCs such as CdTe, CZTS, SnS, etc. The results for Cu doped CdTe thin films are useful for use as absorber layer in TFSCs. Further findings of dependency of physical properties on elemental composition and annealing of (SnS)x- (Bi2S3)1-x graded thin films are useful for applications of these nontoxic materials as layer in TFSCs. Furthermore, physical properties of Cu:SnS thin films were also explored for the use of these materials as layer. Interfacial layer being an important part of TFSCs, Cu doped ZnTe thin films with low resistivity are valuable for an interfacial material at back contact.
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مولاناسید انور شاہ

مولانا سیّد انور شاہؒ
دین و دانش کی دنیا کا مہرانور ۳؍ صفر ۱۳۵۲؁ھ (۲۹؍مئی ۱۹۳۳؁ء) کی صبح کو دیوبند کی خاک میں ہمیشہ کے لئے غروب ہوگیا، یعنی مولانا سید انور شاہ صاحب جانشین شیخ الہند و صدر المدرسین دارالعلوم دیوبند نے دوبرس کی علالتہ بواسیر اور ضعف و نقاہت کے بعد ۵۹ برس کی عمر میں وفات پائی، مرحوم کا وطن گو کشمیر تھا، مگر تعلیم سے فراغت کے بعد ایک مدت تک مدینہ منورہ میں اقامت کی، پھر واپس آکر استاد کی خواہش اور اصرار سے دارالعلوم کی صدارت کی ذمہ داری قبول فرمائی، اور جس کو حضرت شیخ کے زمانۂ جنگ میں ہجرت کے بعد سے ۱۹۲۹؁ء تک اس طرح انجام دیا کہ چین سے لے کر روم تک ان کے فیضان کا سیلاب موجیں لیتارہا اور ہند اور بیرون ہند کے سینکڑوں تشنگان علم نے اس سے اپنی پیاس بجھائی۔
مرحوم کم سخن لیکن وسیع النظر عالم تھے، ان کی مثال اس سمندر کی سی تھی جس کی اوپر کی سطح ساکن لیکن اندر کی سطح موتیوں کے گراں قیمت خزانوں سے معمور ہوتی ہے، دو وسعت نظر، قوتِ حافظہ اور کثرت حفظ میں اس عہد میں بے مثال تھے، علوم حدیث کے حافظ اور نکتہ شناس، علوم ادب میں بلند پایہ، معقولات میں ماہر، شعر و سخن سے بہرہ مند اور زہدہ و تقویٰ میں کامل تھے، اﷲ تعالیٰ اپنی نوازشوں کی جنت میں ان کا مقام اعلیٰ کرے کہ مرتے دم تک علم و معرفت کے اس شہید نے قال اﷲ و قال الرسول کا نعرہ بلند رکھا۔
مرحوم کو سب سے پہلے ۱۹۰۶؁ء یا ۱۹۰۷؁ء میں دیوبند میں دیکھا، جب وہ اور مولانا حسین احمد صاحب مدنی سرزمین عرب سے تازہ وارد ہند تھے، مدرسہ دیوبند میں میری حاضری کی تقریب سے طلبہ اور مدرسین کا ایک جلسہ...

شیخ عبدالعزیز دباغ کی صوفیانہ فکر کے بر عظیم پر اثرا ت کا تحلیلی مطالعہ

Shaikh Abdul Aziz Dabbagh was a prominent Sufi scholar of the Shdhiliyah order. Owing to his moral excellence and righteousness, he endeavored to rejuvenate the Sufism according to the basic principles of Quran and Sunnah. This study aims at to explore the impacts of Shaikh Abdul Aziz Dabbagh’s ideology about Sufism in the territory of Sub-Continent. His philosophy about Sufism has some explicit and unique features which were different from other Sufis of his time. In his method, he gave special importance to abide by the rulings of Quran and Sunnah firmly rather than the prevailing Sufi traditions and asked his disciples to refrain from un-Islamic practices which were being accepted by other so-called Sufis. In this way, he exposed the genuine picture of Sufism before the world. Resultantly, his ideas were widely accepted in Scholars and masses too. In this study, his teachings about Sufism have been designated in detail and peculiarity from other Sufis has been focused.

Investigation of Interactions in Binary and Ternary Systems Using Various Techniques

Investigation of 1-butylamine(BA)+water(W) mixtures (the system) is almost lacking in the literature. This work deals with systematic study of the system and its solutions of alkali metal bromides using various techniques. Both the components of the system have two labile hydrogens each on the same atom of their molecules and are mutually miscible in all proportions. The system also exhibits good solubility for various electrolytes; bromides of four different alkali metals have been selected for the study so that (with all other conditions same) any ‘change’ of the solution property on varying the electrolyte may be attributed to the size and other related parameters of the cation. Measurements of density, viscosity and electrical conductivity have been carried out by systematically varying composition of the system, concentration of the electrolytes and temperature, over the respective suitable ranges at appropriate intervals while dielectric relaxation (DR) spectroscopy was carried out only at 25 oC. The collected data have been interpreted and analysed according to the corresponding pertinent models and schemes. Density measurement on the system has revealed non-ideal mixing which is further substantiated by the isotherms of viscosity (ηmix), excess viscosity (ηE) and excess Gibbs free energy of activation of flow (G*E) as well as the plot of activation energy of viscous flow (Ea); all of them exhibit maxima at a common xBA=0.2. It has thus been concluded that maximum (internal) structure prevails in the system at xBA=0.2 plausibly due to replacement of weaker BA-BA H-bonds by the relatively stronger BA-W ones as well as due to further strengthening of W-W H-bonds caused by the hydrophobic interaction; it has been also inferred that this composition corresponds to ‘optimum H-bonding’ in terms of number and quality both. Same position of the viscosity maximum for different isotherms indicates that no ‘significant’ structural change occurs in the system by changing the temperature (at least within the investigated range). Overall stronger becoming of the intermolecular interactions (IMI) in the system is also indicated from negative excess molar volume (VE) over the entire composition range. The above noted excess quantities were fit to the Redlich-Kister equation to determine the corresponding coefficients. The mixtures were subjected to broadband DR measurement over the frequency range of (0.2 ≤ ν ≤ 89)/GHz. Since complete dielectric loss was not observed upto 89 GHz, the measurements for some selected mixtures were extended to 2.4 THz at which the complete loss could be achieved. The DR spectra were fit to various pertinent models; spectrum of BA got resolved into only two relaxation modes about 50 GHz and 1 THz while the system exhibit an additional mode at 10 GHz indicating (H-bonded) iii association amongst the BA molecules besides co-operative association between the BA and W. Analyses of the relaxation amplitudes have revealed that the ‘effective hydration number’ of BA molecules depends on the mixture composition starting from ~1.5 at xBA=0.03 down to 0.05 at xBA=0.80 thereby suggesting that water molecules are mutually shared by BA when the latter is in excess. Similarly ‘effective dipole moment’ determined for the system varied from 4.68 D at xBA=0.03 to 1.33 D at xBA=0.90 (the reported values for neat water and BA being 2.39 D and 1.75 D, respectively). All the solutions exhibit almost linear increase of density with the electrolyte molality (m) and the slope furnishes ‘density index’ [gρ(x1)] which can be used to quite accurately predict solution density at any mixture composition and m. The g-values follow the sequence: gρ(CsBr) ˃ gρ(KBr) ˃ gρ(NaBr) ˃ gρ(LiBr); partial molar volumes of the electrolytes at infinite dilution ( ϕ V) also follow the same sequence. Viscosity (η) of solutions generally increased with m at all the compositions and temperatures; the exceptions being solutions of KBr and CsBr in (water-rich) mixtures at xBA=0.1 and 0.2. Generally the η–m isotherms were linear and the corresponding ‘viscosity index’ [gη(x1,T)] shows dependence on temperature as well. Like the neat mixtures, each η–xBA isotherm also tends to pass through maximum at xBA=0.2 indicating that the maximum structure was maintained by the mixture upon added electrolyte. Application of a ‘modified Jones-Dole equation’ to the solutions has revealed that KBr and CsBr act as structure-breakers for the more structured (water-rich) mixtures having xBA=0.1 and 0.2; as the structure of the two mixtures is successively made to destroy by increasing temperature, the structure-breaking ability of the two electrolytes also diminished. Ea determined from the temperature-dependent viscosity measurement were quite comparable to the mixture values; Ea–xBA isotherms for all the solutions also exhibit maxima at x1≈ 0.2. All the solutions exhibit increase of electrical conductivity (κ) of the solutions with m and temperature (κ–m isotherms are linear). For a given set of conditions, both KBr and CsBr solutions exhibited quite high and comparable values of κ while LiBr solutions show the lowest values; a plausible explanation is the structure-breaking behaviour of K+ and Cs+ which tend to decrease the so-called micro-viscosity in the vicinity of their rather lesser compact solvates. Variation of κ with temperature change has been correlated with ‘thermal co-efficient of conductivity’ (g) which was almost independent of the electrolyte and its m but changed with composition exhibiting maximum value at xBA=0.2. For an electrolyte the molar conductivity at infinite dilution (Lo) changed with both xBA and T; higher values of the Walden product (WP ≡Lo×ηmix) were found for the water rich region. Under a given set of iv condition the WP follows the sequence: of WP(Li+) < WP(Na+) < WP(K+) ≈ WP(Cs+). From the κ–T-1 plots, values of the corresponding ‘conductivity activation energy’ (Ea) have been determined; the Ea−xBA plots tend to pass through maximum at xBA=0.2. All the electrolyte solutions were subjected to DR measurement within the frequency range from 0.2 to 89 GHz. Symmetrical DR spectra could be adequately explained by a single Cole-Cole (CC) model which furnished time of relaxation (τ), ‘amplitude’ (S) of the relaxing species and relative permittivities (εj). In a given mixture τ increased with m whereas the τ–xBA plots tend to pass through maximum at xBA ≈ 0.2; similar behaviours were also shown by η of the solutions. Thus enough evidence has become available from the study to conclude that BA+W is highly associated system having maximum ‘association & structure’ at xBA=0.2, a mixture composition that corresponds to four W molecules per BA molecule.