SYNTHESIS OF COPPER NICKEL TIN SULPHIDE (CNTS)
USING SOLGEL METHOD
Under Guidance of
Dr. R. Thangavel
Department of Applied Physics
Indian Institute of Technology (Indian School of Mines), Dhanbad
B.Tech (7th Sem )
I would like to express my heartfelt thankfulness to the Applied Physics Department of Indian Institute of Technology (Indian School of Mines), Dhanbad for giving me the chance to do the project work. I am thankful to my project guide Dr. R. Thangavel, Department of Applied Physics, IIT (ISM), Dhanbad, who had given me the opportunity to work under his supervision and encouraging me to undertake this project work and providing valuable suggestions and all kinds of facilities time to time in completing this project.
I would also like to extend my special thanks to Mr. Akash Sharma, Ms. Pooja Sahoo who took lot of efforts to train me and extended cooperation at all time. I take this opportunity to express my deep sense of gratitude towards Mr. Zeeshan Anwer, Mr. Jorge Boro, Mr. B. Virajit and Mr. Abhijit for helping me a lot in my work and was ever willing to engage in thoughtful discussions. Last but most important, I want to thank my parents whose consistent support, encouragement and blessings helped me to carry out my work peacefully.
The energy demands of the world are increasing exponentially and we getting almost 84% of the current energy supply from fossil fuels. The drawback of fossils fuels are that they are a non-renewable source of energy with a significant carbon footprint. The quantity of CO2 liberated in the earth’s atmosphere as a result of the burning of fossil fuels is bewildering due to which the quantity of and adds meaningfully to global warming and climate alteration. Human population and the survival of the human race will be afftected wildly in near future, that’s why it is necessary to find substitution for energy sources that are spotless, green and renewable. There are many source of energy like solar, wind, tidal, geothermal and nuclear. We can obtain energy from sun in one day is more than energy spent by total world population in a year. Vitality collecting through solar photovoltaics is on the foremost edge among other renewable energy means.
Approximately 85% of the total photovoltaic market is the silicon-based solar cells. This may because of the presence of major amount of Si on the earth in adding to the fact that the progress mechanism of high-quality Si thin films is well-advanced in the semiconductor industry for mass construction. The important important in marketing solar cell technology are the high industrial costs and the non-obtainability of different techniques to increase the cell proficiency. The cost of the materials used for the solar cell production is focal spending. Hence, it is urgent need to decrease the material cost to make high proficient solar cells suitable popular common household uses. It is pretty documented that 40% of the expense of solar cell fabrication is in the materials side, and therefore any decrement in the amount of material can lead to a reduction in the cost of solar cells. The straight optical band gap of chalcogenide based solar cells provide the advantage of high fascination in contrast to silicon. Moreover, the band gap tunability either by metal or chalcogenide replacements can enhance the absorber band gap as per the solar spectrum. To make solar energy obtainable for worldespread use to the common masses, the absorbing materials should be minmum cost, non-toxic, earth copious and provide a similar or better effectiveness and generation than standard silicon solar cells. The straight band gap chalcogenide thin film photovoltaics (PVs) through higher absorption than silicon could permit the construction on module rule. Newly, CuInGaSe2 (CIGS) based solar cells display world record productivity of 21.7% on the workroom scale but materials like In, Ga and Te are expensive and rare. Hereafter this cannot be used for the increase of Terawatt (TW) energy sources to meet the energy demands of the world.
There are numerous applicants for the growth of earth plentiful photovoltaics such as Cu2ZnSnS4 (CZTS), SnS, Cu2O and FeS2. Among these CZTS are actual capable as competences beyond 12% have already been attained. Therefore materials with equivalent structures similar band gaps and absorption coefficients as CZTS such as Cu2MSnS4 where (M = Ni) have involved a great contract of consideration for earth profuse thin film solar cells. Earth abundant, nontoxic and cost-effective CNTS offers high absorption coefficient ~ 104 cm?1 and optimal optical band gap of 1.4 eV – 1.6 eV. Theoretical studies reported that the replacement of Ni for Zn in CZTS compound has the probable to augment electrical conductivity and decrease the optical band gap.
The impartial of this work is to create Cu2NiSnS4 (CNTS) thin films at dissimilar temperature and explore its electrical and optical possessions and apply it in photovoltaic devices. The first step towards attaining these goals is to synthesize Cu2NiSnS4 (CNTS) solution using a simple, simplistic and solution handled technique like sol gel. This will be shadowed by making thin film using gyration coating. And lastly the temperature is optimised by examining electrical and optical properties. The research innovations would be the mixture of crystalline CNTS thin films by a solution treated technique and considerate the electrical conveyance and photocarrier group in these thin films.
DEPOSITION TECHNIQUES FOR CNTS THIN FILM:
In evaporation method Ni, Sn and Cu layers were successively dumped on glass substrates which were animated up to 150oC. The besieged arrangement ratio was obvious by the thickness of metallic layers. Hardening at 500oC in the atmosphere of N2 + H2S (5%) was then working to convert Cu/Ni/Sn stacked layers into a CNTS thin film.
It is examined the electrical and optical properties of CNTS thin film which was dumped on slide glass substrates by atom beam popping. The dumped CNTS thin film solar cells was polycrystalline.
In this method, Copper chloride, tin chloride were distinctly liquefied in a combination solution holding NaOH and sorbitol. Metal layers were potentiostatically dumped at room temperature in the order Cu, Sn, Ni using a predictable 3-electrode electrochemical cell with a platinum counter electrode and Ag/AgCl reference electrode. The electroplated metallic films and sulphur powder were overloaded into a graphite container, which was introduced into a oven tube. CNTS thin films were then synthesized at 550oC by the sulfurization of the electroplated metallic films.
For synthesis of Copper Nickel Tin Sulphide, the sol-gel method was used. It is a wet-chemical method that usages either a chemical solution or colloidal elements to harvest an combined network (gel). Sol-gel technique is to make the readily hydrolysable metal compound (inorganic salts or alkoxides) respond with water in convinced solvents, forming Sol through the process of hydrolysis and polycondensation and make Sol form fluid film on substrate by dipping or spin-coating method; after gelatinisation, it can be altered into formless form (or crystalline) films by heat dealing.
WHY WE ARE USING SOL-GEL METHOD TO DEPOSIT CNTS THIN FILM?
A particular challenge for fabrication of CNTS is the volatility of certain elements (Sulphur) which can evaporate after a certain temperature. Sol-gel method is low temperature method. Sol-get method is cheaper than other methods for deposition of thin film. We want to deposit thin film and from sol-gel method thin metals oxide/sulphides can be obtained. Sol-gel method is simple and economic and effective. By using sol-gel method we will get uniform nanostructure and highly pure products.
Preparation of CNTS Thin Film:
Magnetic stirrer, magnetic beads, ultrasonic cleaner, spin coater, heat oven, weighing machine, etc. along with ITO coated glass, flask, beaker, Petri dish, droppers, thermometer, etc.
Fig- Glass Cleaning Method
Glass substrates were placed in an ultrasonic cleaner with Piranha solution (Piranha solution is mixture of H2SO4 and H202 in 3:1 ratio) for 2 hours. Then the substrates were placed in DI water (Deionized water) for 20 minutes. Then the substrates were placed with Acetone for 20 minutes. Again the substrates were placed with DI water for 20 minutes. Now the substrates were treated with Ethanol for 20 minutes. Again the substrates were treated with DI water for 20 minutes for final cleaning. Finally the glass substrates were kept in the oven for drying. We use DI water between each step to remove the previous solution from the glass substrates.
Preparation of CNTS Solution:
Precursors used are:
S.No. Chemical Name Formula Molecular Weight
1 Copper Chloride Dihydrate (CuCl2.2H2O) 170.48g/mol
2 Nickel Acetate hydrate Ni(CH3COO)2.H2O 3 Thiourea (CH4N2S) 76.12g/mol
4 Tin Chloride Dihydrate (SnCl4.2H2O) 225.63g/mol
5 2-Methoxy Ethanol (C3H8O2) 76.09g/mol
6 Monoethanolamine(C2H7NO) 61.08g/mol (Density=1.015Kg/m3)
We dissolved all precursors in 2-methoxy ethanol separately at 60°C. After all the precursors gets dissolved, we then mix the chlorides one by one, putting Thiourea at the end, then solution was stirred maintaining temperature at 60°C for 30 minutes, while stirring .3 ml monoethelenamine (MEA) was added drop wise. After stirring, the solution was filtered. The filtered solution was spin coated on the substrates like glass/ITO/Si etc.
CNTS thin films were deposited by spin coating method onto cleaned glass substrates. The solution was dropped onto glass substrate, which was rotated at 3000 rpm, for 30 second by using spin coater.
Spin Coating Unit