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APPLICATION FOR FINANCIAL SUPPORTContribution to Alma Matter Project (CAMP)

By

Prof. A. Vasudeva Adhikari, NITK, Surathkal, DK.E mail: avachem@gmail.com Ph: 9448627138

1. Name of the Project2. Name of the Investigator with email id3. Project Objectives4. Key Deliverables / Outcomes5. Estimated Cost

1. Title of Research proposal:

“NEW CYANOPYRIDINE BASED CHROMOPHORES FOR HIGHLYEFFICIENT SOLAR CELL APPLICATION”

Brief Introduction:

A low-cost and environmentally friendly alternative to conventional Si based solid-state devices is the dye sensitized solar cells (DSSCs). DSSCs are a class ofphotoelectrochemical cells, which converts solar light to electric energy. It is inexpensiveto prepare, and the light-weight thin-film structures are compatible with automatedmanufacturing and thus potentially has easy scaling possibilities. In addition, it showsgood performance under weak/diffused light, and compatibility with building windowglass and on flexible substrates (Hashmi et al., 2011). Amongst the four components ofDSSC, sensitizer plays an important role. Organic dyes with appropriate structures are thepotential candidates for sensitizers. Till date, use of organic dyes as sensitizers hasreached the maximum efficiency of 13% in the device (Mathew, S. et al., 2013). So, thereis an ample of scope for the improvement in the efficiency, if an efficient sensitizer isused.

Several organic chromophores (n-type) have been reported as effective sensitizersin DSSC. Also, their structure and device characteristics have been correlated. Based onthe literature reports, it has been thought of designing new n type organic chromophoresas effective sensitizers for DSSC application (Mishra et al., 2009; Albero et al., 2015). Ithas been planned to synthesize newly designed molecules using standard syntheticmethods. Finally, it has been intended to fabricate DSSCs using newly developedchromophores, keeping semiconductor and electrolyte unchanged in the cell. It has beenalso contemplated to study the effect of structure of chromophores on device parameters(Naik, P et al., 2018). It is hoped that new sensitizers would lead to improved efficiencyand give valuable information about structural dependence on efficiency of DSSCs.

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2. Type of Project:

Applied Area of Research

3. Objectives of the Research Proposal:

The major objectives of the research proposal are as follows:

1. To fabricate new dye-sensitized solar cells using the new chromophores as sensitizersby using the Doctor Blad method

Following are the sub-objectives:

(i) To design new D-π-A, D-D-π-A type organic chromophores carrying differentdonar units such as phenothiazine, carbazole, indole, triphenylamine,diphenylamine units as donor with different π-spacers and accepting/anchoringgroups as n type sensitizers

(ii) To synthesize newly designed n-type organic chromophores using simplesynthetic routes and optimize the reaction parameters

(iii)To characterize the newly synthesized intermediates and target dyes by FTIR,1H-NMR, 13C-NMR and Mass spectral techniques followed by elementalanalysis, and finally by single crystal X-ray diffraction study

(iv)To evaluate their linear optical properties by means of UV-visible absorptionand fluorescence emission spectroscopy

(v) To determine their electrochemical properties, charge carrying properties andband-gaps using cyclic voltammetry

(vi)To study electronic distribution in HOMO-LUMO using Turbomole V 7.2software package at the def-TZVPP level

2. To carry out photovoltaic performance studies of new chromophores or theircombinations in photovoltaic device with respect to efficiency, stability, morphologyand thickness of titania film and other related parameters

3. To optimize the parameters for improved performance with the aim of achieving amaximum monochromatic incident photon-to-current conversion efficiency of 90%, ashort-circuit photocurrent density more than 16 mAcm-2, an open-circuit photovoltageof 800 mV, a fill factor of 0.7 and an overall conversion efficiency of 8.5 % understandard global AM 1.5 solar light conditions. Optimization parameters include size oftitania, film thickness, dye concentration, conductivity of electrolyte, temperature,environmental conditions and other related parameters. Exploration of structure–property correlations of new dyes in the context of cell efficiency is also involved.

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4. To investigate the co-sensitization properties of newly synthesized dyes along withwell-known Ruthenium based sensitizers

4. Details of Investigators

(a) Principal Investigator

Name & Designation:

Dr. A. Vasudeva Adhikari, Professor of Chemistry

National Institute of Technology Karnataka, Surathkal, Mangalore-575 025, DK

Ph: Off: (0824)2474000, Extn: 3203; Res: (0824)2474203; Mob: +919448627138

Fax: (0824)2474033; or (0824)2474039

Email: avachem@gmail.com, avadhikari123@yahoo.co.in, avchem@nitk.ac.in

(b) Collaborating Investigator

Name & Designation:

Name and address of Institution complete with phone no., mobile, fax and e mail:

Dr. Ahmed El- Shafei

Fibre and Polymer Science Program, College of Textiles, 1020 Main Campus Dr,Raleigh, North Carolina State Universiy (NCSU) 27606, USA

Professor, Room 3119 Polymer and Color Chemistry Department

Email: ahmed_el-shafei@ncsu.edu Phone: 919-515-6548

5. Proposed duration of the research proposal:

Two years

6. Amount of grant proposed for:

Proposed expenditure on Year IRs. inLakhs

Year 2Rs. inLakhs

Line TotalRs. inLakhs

a) Staff - JRF @ 25,000/- per month 2.40 2.40 4.80

b) Expendables (Chemicals andGlasswares)

0.40 0.40 0.80

c) Travel 0.30 0.30 0.60

d) Contingencies 0.30 0.30 0.60

Column totals 3.40 3.40 6.80

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Justification:

(a) Staff (Designation, number and pay for each post to be given)

It is intended to appoint a JRF to carry out synthetic work and characterization ofnewly synthesized compounds. The selection will be based on Institute’s norms.Selected candidate is supposed to design the structures of new dyes based on HOMO-LUMO calculations, using Turbomol software. He/she has to develop synthetictechniques and purification methods to get pure dyes. His/her other responsibilitiesinclude writing yearly and final project reports, papers for publication and attendingconferences. The selected candidate will be paid Rs. 20,000/- per month as stipend fortwo years.

(b) Expendables (Chemicals, Substrates, Glasswares, Photographic materials, etc.)The planned research proposal includes experiments involving synthesis, optimizationof synthetic protocols and conditions and finally purification of synthesized molecules.Lots of common chemicals, rare-chemicals and fine-chemicals are to be procured forsynthesis. We need solvents for purification of new molecules. Glasswares likereactor, distillation assembly round bottom flasks, filtration assembly, condensers,guard tubes, distillation assembly with ground glass joints are to be purchased.Costly ITO plates are to be procured for preparing DSSCs. Coating of TiO2 to arequired thickness is very important work in our research. Certain adhesives andsurface active chemicals are in need to enhance the overall efficiency of DSSCs.

(c) Travel (only Domestic)A part of money has been assigned for travel required for investigators as well as JRFwith regard to research activities. The investigator’s group will visit IISc and IITs forlibrary reference work. A part of travel grant will be used for attending nationalconferences in order to interact with other scientists in the same area. Sometimes,grant may be used to meet subject experts of other Institutes personally for discussingon the research problems.

(d) Contingencies (Postage, Stationary, Typing, Miscellaneous etc.)A part of expenditure is earmarked for postage and purchase of stationary items likepen, pencil, gum, paper, stapler, scissor, blades etc. required for preparation of projectreports and other related work. Also, the expenditure under this head includes mainlypurchase of toners, replacement of old parts of computer/printer, typing charges, andother miscellaneous payments.

7. (i) Departments of the Institution where research work will be carried out:

Department of Chemistry, NITK, Surathkal, DK.

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(ii) Other Departments, if any, which will cooperate in this study.

Fibre and Polymer Science Program, College of Textiles, 1020 Main Campus

Raleigh, North Carolina State Universiy (NCSU) 27606, USA

8. Summary of the work

Dye-sensitized solar cells (DSSCs), belonging to a group of thin film photovoltaictechnologies are a promising low cost alternative to existing crystalline siliconphotovoltaic technology. This was discovered by Gratzel and O’Regan (Grätzel M. etal.,1991).The DSSC or Gratzel cell, is a complex system wherein three differentcomponents, viz. the dye, the semiconductor and the electrolyte are brought together togenerate electric power from light without undergoing any permanent chemicaltransformation. Dye-sensitized solar cells (DSSCs) have attracted considerableattention after Gratzel’s discovery because of the following reasons: Efficient use of DSSC can meet our increasing energy demand

It is environmentally friendly. Organic dyes as sensitizers own advantages of easy production and design

versatility

Highly economicalGenerally, DSSCs make use of various chromophores including inorganic

complexes and metal-free organic dyes, as efficient sensitizers (Grätzel, M. 2001).The DSSC research field can be an exciting playground for synthetic and materials

scientists. Unlike solar cells based on single material semiconductors, DSSCs haveseveral key components which allow numerous innovative approaches. It has beenpossible to design DSSC panels which are flexible, lightweight versions based onpolymer supports in lieu of glass substrates (ideal for portable electronics), withoptically translucent TiO2 layer (Li B.,et al., 2016).

Till date, several organic chromophores (n-type) have been reported for DSSCapplication; therefore it will be a herculean task to give an account of all the dyes.Design and synthesis of efficient dyes, and the identification of parameters limiting theperformance of dye sensitized solar cell are really challenging tasks. By modifying thedye structure, the optical properties as well as the energy levels will be altered, whichhad a large effect on the light harvesting ability and different charge transfer processes(Hagberg, D.P.,et al.,2008).

With regard to dye-design, it is of interest to increase the life-time of the charge-separated state by introducing the conjugated π-linkers either between the anchoringgroup and the electron-donor, or between the electron-donor and electron-acceptor,and by introducing shorter alkyl chains close to the anchoring group in order to protectthe surface. In addition, dyes with broad absorption spectrum, high molar extinction

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coefficient, good stability and strong binding ability should be considered forimproved efficiency (Qin, H.,et al.,2008).

9. Scientific Importance of the Project

Today, solar power accounts for only 0.54% of global energy usage. Theaverage annual market growth of the photovoltaic industry has been 35-40 % forseveral years. Propelled by aggressive research and development (R&D) activities(Green M. A.,et al.,2018),third generation photovoltaics (PVs) are poised to take ahuge leap forward. In this context, DSSCs are future potential candidates forharvesting abundant solar energy.

10. Specific technology fall-outs:

According to company expert reports, there are many “formidable challenges”for manufacturers of DSSCs devices to overcome. Topping the list, it says, is thepower conversion efficiency (PCE). Some of the fundamental issues that must beaddressed are band-gap, interfaces, and charge transport. If these bottlenecks are dealtwith, the prospects of gaining a better share of the commercial market will beenhanced.

The optimum PCE values are yet to be achieved because the methods to allowmorphology control and the principles that underpin them are still being heavilyresearched upon. The experts from the company opine by saying that higherefficiency, enhanced stability, extended lifetime, reduced cost and materialperformance are some of the core areas of research for the joint ventures pursued byboth government and private organizations. Focus on optimization of the productionprocess, prototype development, effective encapsulation, large-area, and large-scalemanufacturing, as well as streamlining distribution will put the market on the fasttrack to progress.

Strategies for the improvement of DSSCs:

The major technical challenges:In light of the recent advances within the field of organic photovoltaics with

respect to stability and power-conversion efficiency, the current challenge is theindustrial demonstration of a low-cost organic photovoltaic module with moderatestability and efficiency. The secondary challenges are a higher stability of more than10 years and efficiencies above 10%. Most notably, the demonstrations of moderateefficiency, high stability and large-scale processing have not been demonstrated forthe same material. However, the fact that isolated studies can reach any of the threegoals does hold promise for the possibility of combining all three goals in the same

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material, and this is the overall current challenge known as the unification challenge.To conclude, major technical challenges include:

Low DSSC power-conversion efficiencies

Low stability of DSSCs Corrosive nature of iodide redox couple

Inability for harvesting the whole spectrum of light ranging from visible toNIR light

High internal resistance

Low internal and external quantum efficiency Unnecessary aggregation of dye molecules

Costlier transparent conducting electrodes for DSSCs Proper fabrication methods i.e development of thin layer technology for

continuous production

Required modifications:

Dye molecules can be modified to increase the range of wavelengths acrosswhich light can be absorbed.

Absorption power of the dye system can be improved by mixing two or moredyes with different absorption wavelengths to expand light absorptionwavelength range.

The efficiency of existing Ru based dyes by the process called co-sensitizationtechnique.

Photoelectric conversion of the dye can be increased by slowing down thepassage of electrons from the dye molecules to the electrode and by hinderingthe flow of electrons from the dye molecules into the TiO2 through properselection of dye components.

Light absorption can also be enhanced by increasing the amount of dyemolecules adsorbed to the titanium dioxide surface.

Internal resistance can be reduced by modifying the electrode structure andelectrolyte.

The efficiency of the solar cell module can also be enhanced by increasing theaperture ratio.

Against this background, we are interested to design and synthesize new classof dyes and study their sensitizing efficiencies in liquid-junction DSSCs. Further, byusing highly efficient dyes, it has been planned to conduct series of experiments withvarying electrolyte system, redox system and size of TiO2 in order to develop a DSSCwith improved performance. Further, it has been thought of commercial developmentof the DSSC panels for particular applications.

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Prospect of commercialization

In the future photovoltaic market DSSCs will compete depending on:

(i) Our ability to increase power-conversion efficiencies and develop ultralow-cost architectures that are stable over 20 years.

(ii) Overall photovoltaic demand and the scarcity of rare elements.(iii) Cheap metal foils (such as stainless steel and aluminium) and plastic sheets

could be used to make Ultralow-cost DSSCs.(iv) Cheaper transparent conducting electrodes for DSSCs must therefore be

developed to match the efficiency of glass-based designs.(v) To increase the life time of DSSCs we have to think of electrolytes that are

less corrosive than iodide.(vi) Increasing the module efficiencies of DSSCs to more than 14% would

reduce the ultra low-cost constraints, thus providing substantial incentive tocreate laboratory-scale devices with efficiencies greater than 15%.

(vii) Further increasing efficiencies up to 15% with a dye capable of absorbingup to 920 nm.

Development of new DSSC with enhanced efficiency and its module designrequire a great deal of further investigation into overall lifetimes and degradationmechanisms of DSSC.

The expected outcomes of the proposed project are as follows: Fabrication of DSSCs using newly synthesized dyes with suitable electrolytic

system (such as cobalt based redox couples with lower potential or solid state holetransport) following the established technique. This also includes design anddevelopment of synthetic methods for the synthesis of new organic dyes with highUV, Visible and NIR absorption characteristics.

Development of optimized DSSCs with improved performance, i.e. achievement ofmaximum monochromatic incident photon-to-current conversion efficiency of 90%,a short-circuit photocurrent density of 16 mAcm-2, an open-circuit photovoltage of800 mV, a fill factor of 0.7 and a overall conversion efficiency of 8% under standardglobal AM 1.5 solar light conditions and stability. Optimization with respect to sizeof titania, dye concentration, solvent, temperature, and other related parameters.

Contribution of significant research in the area of photovoltaics for the developmentof cheaper and efficient DSSC with better performance for harvesting solar energy,to reach the common man in the society.

11. Methods and Procedure:

Design of New Sensitizers for DSSC:As per the literature report, the introduction of cyanovinylene group to the

molecular core resulted in the reduction of band gap and as a result an increase in λmax

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values. Further, this molecule exhibited light harvesting efficiency of near unity andan IPCE of 80% (Wang et al.,2007). Further, the desired optical properties can beachieved when new conjugated systems are composed of donor-π bridge-acceptor (D-π-A) segments with different heterocyclic systems which allow the fine tuning ofimportant physical and/or photo-physical properties. Such aromatic D-π-A typemolecules with push-pull mechanism are quite stable and they can act as potentialdyes for DSSC. Ever since the introduction of DSSC many sensitizers have been usedsuch as coumarine, carbazole, triarylamines etc. The π-conjugation linkers typicallyused are chain of ‘n’ units (generally 4 to 8) or aromatic moieties such as phenylene,thiophene etc. the most commonly used acceptors is cyanoacrylic acid, whichcombines the electron withdrawing properties of cyano group with the carboxylicanchoring group. Other anchoring groups used are rhodanine-3-acetic acid,phosphonic acid, silanol etc (Koumura,N.,et al.,2006). in order to gain a better insightinto the effect and contribution of different components we have framed a strategywherein it has been planned to one of these part at a time. Keeping this in view, newsensitizers consisting of different π-conjugated donor and acceptor moieties have beendesigned.

In this new design, different electron donating moieties (phenothiazine,triarylamine, indole, and coumarines) are linked to π-bride via cyanovinylene group.In all the cases the π-bridge and the acceptor units are kept constant. Due to thedifference in the electron donating ability of the donor groups as well as conjugationpath length it is expected that these sensitizers will show variable optical andelectrochemical properties. Also, we expect a bathochromic shift in the UV profile ofthe newly synthesized dyes which in-turn will enhance the light harvesting efficiencyand eventually the the overall efficiency.

Fig. 1 Newly designed dyes

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Similarly some new molecules have been designed by keeping the donor andacceptor unchanged and by varying the π-spacer groups, as show in fig. 2. Thisdesigned is based on the observation that the replacement of thiophene byphenylenevinylene and ethylenedioxythiophene groups have resulted in an increasein Jsc and Voc values leading to an increment in cell efficiency. Also, the introductionof thienothiophene core lead to an improved efficiency suggesting that the rigidthienothiophene could well be an excellentent π-conjugated system for DSSC.

Fig. 2 Newly designed dyes with different π-conjugation groups

According to literature reports (Becke, A.D. 1993), the anchoring groups alsoplay a pivotal role in the overall efficiency of DSSCs; this is because the anchoringgroups are responsible for the charge injection from the LUMO level of the dye to theconduction band of TiO2. Keeping this in view, it has been planned to investigate theeffect of change in anchoring groups on the efficiency of solar cells. It has beenplanned to keep the donor and π-spacer as unchanged and to alter the anchoringgroups shown in figure 3, which may help us to have a deeper understanding of theeffect of anchoring groups on DSSC performance.

Fig. 3 Design of new n-type sensitizers with different anchoring groups

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According to literature the auxiliary donor groups also play a pivotal role in theoverall efficiency of DSSCs; this is because the auxiliary donor groups are responsiblefor the charge donation from the HOMO level to the LUMO of the dye (Becke, A.D.1988). Keeping this in view, it has been planned to investigate the effect of auxiliarydonor groups on the efficiency of solar cells. It has been planned to keep the donor andπ-spacer as unchanged and to alter the anchoring groups shown in fig.4, which mayhelp us to have a deeper understanding of the effect of anchoring groups on DSSCperformance.

Fig. 4 Design of new n-type sensitizers with different π-conjugation groups

Reactions schemes have been proposed for synthesis of newly designedmolecules. These compounds will be synthesized by following standard syntheticprotocols. A brief methodology for their synthesis, characterization followed byfabrication of DSSC properties is described below.

Synthesis:

Thus, four series of new sensitizers will be synthesized according to the schemesmentioned below.

Series 1:

Scheme 1

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Series 2:

Scheme 2Series 3:

Scheme 3Series 4:

Scheme 4

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Structural characterization

The formation of new compounds will be confirmed by spectral techniqueslike FTIR (for the identification of presence of functional groups), 1H NMR (fordetermining the types of proton within the molecules) and 13C NMR (for theidentification of carbon atoms in the molecule). The purity as well as molecularformula of new compounds will be confirmed by mass spectral analysis (LCMS -powerful technique used for the percentage purity, identification of molecular formulaand determination of molecular mass). In addition, single crystal X-ray analysis willbe carried out for selected compounds to confirm their structures. These facilities willbe taken from Manipal Institute of Technology, Manipal.

Fabrication of DSSC device:

It has been planned to fabricate DSSC using the newly synthesized dyes. Thefabrication of the DSSC will be carried out by following the Doctor Blade method(Hashmi G.,et al.,2011). A paste consisting of 20 nm sized TiO2 particles (CICC,PST-18NR) was applied with a scalpel on a fluorine-doped SnO2 (FTO,PilkingtonTEC-8 glass, 6e9 Ohms/sq with 2.3 mm thickness) conducting glass andthen air-dried for 2 h. This TiO2 film was gradually heated at 325oC for 5 min, at 375oC for 5 min, at 450 oC for 15 min, and at 500 0C for 15 min. The second layer is air-dried and then sintered in the same way as the first layer. The TiO2 electrodes wereimmersed in 40mM aqueous TiCl4 solution at 70 0C for 30 min, washed with waterand ethanol and heated at 500 oC for 30 min. After cooling to 800C, the TiO2

electrodes were dipped into the dye solutions (0.4 mM ) for 24 hours. The dye-coatedelectrodes were rinsed quickly with ethanol. To prepare a platinum (Pt) counterelectrode, a small hole was drilled in a FTO glass and a drop of H2PtCl6 solution (2 mgPt in 1 ml of ethanol) is placed on the FTO plate followed by sintering at 400 oC for 15min. The dye-anchored TiO2 electrodes and the Pt counter electrodes were assembledin to a sealed sandwich type cell using a thin Surlyn polymer transparent film (SX1170-25, 25 mm) as a spacer between the electrodes. The sandwich cells were lightlycompressed at 110 oC to seal the two electrodes. A thin layer of electrolyte wasintroduced into the inter electrode space from the counter electrode side through pre-drilled holes using vacuum backfilling method. Electrolyte 0.5M4-tert-butylpyridine(TBP) in 2-methoxypropionitrile. The holes were sealed with Surlyn and microscopecover slides to avoid leakage of the electrolyte solution.

Photovoltaic characterization:

The current-voltage characteristics of the devices were carried out undersimulated AM 1.5G irradiation using a xenon lamp-based solar simulator (Oriel 300W solar simulator) attached to Kiethley 2400 source metre and calibrated with acrystalline silicon reference cell (VLSI standards, PVM-495-KG5). The solar cell

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efficiency (η) was obtained with the relation, η= Jsc. Voc FF /Pin, in which JSC (mAcm-2) is the current density measured at short circuit, VOC (V) is the voltage measuredat open circuit, FF is the fill factor and Pin is the input radiation power (for 1 sunillumination (AM 1.5G), Pin = 100 mW cm-2).

Work plan:

The proposed research work will be executed according to the work plan asgiven in the following table and summarized in the bar chart.

Time Schedule Activities

0 - 12 months Library work – Literature survey, Design of new dyemolecules and their synthetic schemes

Procurement of new rare chemicals and solvents. Continual of reference work

Procurement of Instruments Synthesis of newly designed dyes as per the schemes and their

structural characterization by UV-Vis, FTIR, NMR, Massspectral studies including single crystal x-ray studies andelemental analysis

Development of synthetic methods for good yield andpurification techniques for final dyes

Preliminary setting, studies and calibration of instruments Yearly report. Objectives (i) to (vi) will be covered.

13 - 24 months Continual of reference (literature survey) work Development of fabrication technology with controlled

thickness after preliminary experimentations (2 - 3 methodswill be employed to get optimum results)

Continual of reference work, Photocurrent and photo-voltagemeasurements using pre-calibrated solar simulator, Generationof photovoltaic parameters, Photo-physical studies, DFTcalculations, electronic structure calculations to visualizemolecular orbitals

Optical and Electrochemical studies of new molecules andcorrelation of their efficiencies with structures

Co-sensitization studies of new organic samples

2nd Year progress report. Objectives (2), (3) and (4) will becovered.

Paper presentations, publications, preparation and submissionof final project report.

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BAR Chart for the work plan (activities)

Months/ Activities 0 - 6 7 - 12 13 - 18 19 - 24

Literature Survey,Procurement of Chemicals & Instruments

Lit. Survey, Synthesis & Characterization offirst two series, Publications, First report

Lit. Survey, Synthesis, Purification andCharacterization of next two series ofcompounds

Lit.survey,Electro-chemical andphotophysical characterization,publications, II report

Lit. Survey, Preliminary device fabricationstudy, Pilot experiments, Calibration, etc.

Lit. Survey, Device performance Studies ofall the series, Publications, Final report

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1. Name of institution submitting application

National Institute of Technology Karnataka, Surathkal, Mangalore

A Deemed University, Center of Excellence, MHRD, GOI

2. Address

National Institute of Technology Karnataka, SurathkalPost: Srinivasnagar, Mangalore, 575 025, DK, Karnataka State

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3. Name, designation and full address of the official to whom cheques are to be mailed

Prof. Karanam Uma Maheshwar RaoDirectorNational Institute of Technology Karnataka, Surathkal, Srinivasnagar,Mangalore,575025Phone: (0824) 2474000, Ext: 3203; Fax: (0824)2474033.

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