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Crystalline Silicon Solar Cells.pptx

  1. 1. Crystalline Silicon Solar Cells Peeyush Mishra (B191265MT) Kaushlendra Kumar (B191287MT) 1
  2. 2. Contents ● Overview ● Functioning & Structure of Silicon Solar Cells ● Types of Silicon Solar Cells ● Production of Silicon Solar Cells ● Merits and Demerits of Silicon Solar Cells ● Efficiency of Silicon Solar Cells ● Future Prospects & Challenges of Silicon Solar Cells ● Applications of Silicon Solar Cells ● References 2
  3. 3. “Crystalline silicon solar cells have high efficiency, making crystalline silicon photovoltaics an interesting technology where space is at a premium.” 3
  4. 4. Overview. 4
  5. 5. Crystalline silicon photovoltaic (PV) cells are used in the largest quantity of all types of solar cells on the market, representing about 85% of the world total PV cell production in 2011. Overview 5
  6. 6. ● Silicon is the most popular PV material ● Most cells are made from leftover computer chip manufacturing ● Silicon must be refined to almost 100% purity ● The uniform molecular structure of silicon makes it efficient for electric transport ● Silicon wafers are cut from ingots Overview 6
  7. 7. ● Sharp Electronic Corporation ● Sanyo ● Bp Solar ● Shell ● Sunwise ● Uni-Solar ● Astro Power Manufacturers 7
  8. 8. Functioning & Structure. 8
  9. 9. A silicon solar cell works the same way as other types of solar cells. When the sun rays fall on the silicon solar cells within the solar panels, they take the photons from the sunlight during the daylight hours and convert them into free electrons. The electrons pass through the electric wires and supply electric energy to the power grid. The direct current from the sunlight is transformed into alternating current within a solar inverter. It is then made to pass through the cables to charge different devices and appliances. Functioning 9
  10. 10. Structure Typical mono- and polycrystalline silicon solar cells (upper), and simplified cross-section of a commercial monocrystalline silicon solar cell (lower) 10
  11. 11. Types 11 ● Monocrystalline Silicon PV cell ● Polycrystalline Silicon PV cell ● Amorphous Silicon PV cell
  12. 12. Monocrystalline Silicon Solar Cell ● Single Crystal ● Pure Silicon ● Comes in Dark Shade ● Space Efficient ● Works longer ● Expensive 12
  13. 13. Polycrystalline Silicon Solar Cell ● Multiple Crystals ● Less Efficient ● Takes large space ● Works longer ● Cheaper 13
  14. 14. Amorphous Silicon Solar Cell ● Most significant thin film variant ● High absorption capacity ● Maximum Efficiency of 13% ● Cheapest ● Ideal for charging small electronic gadgets- calculator and watches ● Simple design- can be deposited on glass and plastic 14
  15. 15. Production. 15
  16. 16. Czochralski Process ● For monocrystalline silicon PV cell production ● This is the process of creating an ingot ● A small single silicon rod is placed in an inert gas at high temperature ● When the seed is rotated up and out silicon adheres to it and forms an ingot 16
  17. 17. Siemens Process ● For multicrystalline silicon PV cell production ● Made from metallurgical grade Silicon by a chemical purification method ● Involves distillation of volatile silicon compounds and its decomposition at a high temperature 17
  18. 18.
  19. 19. Merits and Demerits. 19
  20. 20. ● Maturity: Considerable amount of information on evaluating the reliability and robustness of the design, which is crucial to obtaining capital for deployment projects. ● Performance: Offers higher efficiencies than any other mass-produced single-junction device. Higher efficiencies reduce the cost of the final installation because fewer solar cells need to be manufactured and installed for a given output. ● Reliability: Reaches module lifetimes of 25+ years and exhibit little long-term degradation. ● Abundance: Silicon is the second most abundant element in Earth's crust (after oxygen) Merits 20
  21. 21. ● Non-Toxic ● Cost Effective ● Good Photoconductivity ● Light weight ● Resistant to corrosion and does not rust easily. ● Handles intense sunlight and high temperatures. ● Low maintenance. ● Can be placed in solar panels and used for residential, commercial, and industrial applications. Merits 21
  22. 22. ● Heavily reliant on weather. ● Humongous space needed to store and accommodate them. ● Installation cost is higher than those of electrical systems. ● Demonstrates intermittent problems. ● Users need to purchase batteries and inverters separately to convert solar energy into electric energy and save the excess for later use. Demerits 22
  23. 23. Efficiency. 23
  24. 24. ● Crystalline Silicon PV cells have laboratory conversion efficiency of: ○ 25% for single crystal cells ○ 20% for multicrystalline cells ○ 13% for amorphous cells ● However, industrially produced solar modules currently achieve efficiencies ranging from 18- 22% under standard test conditions Efficiency 24
  25. 25. Efficiency Best research solar cell efficiencies reported by NREL 25
  26. 26. Efficiency Efficiency of various solar cells over the years presented by NREL 26
  27. 27. Efficiency Simulation of the solar cell efficiency of a double-junction solar cell as a function of light concentration at a temperature of 320 K. 27
  28. 28. Future Prospects & Challenges. 28
  29. 29. ● Efforts being focused on innovative ways to reduce costs ● R&D being done to reduce raw material requirements ,including pioneering ultra-thin crystalline silicon absorber layers, developing kerf-free wafer production techniques and optimizing growth processes. Current Research 29
  30. 30. Developments Reduction of silicon wafer thickness 30 cells_fig30_327467751
  31. 31. ●Selective front diffusions ●Localized back contacts and dielectric back surface passivation ●Metallization ●Wafer crystallinity and conductivity type Increasing efficiency 31
  32. 32. Due to the usage of pricey and high-quality silicon in manufacturing, silicon solar panels used to be extremely expensive. Additionally, the cost of purifying silicon cells was also high. But as technology advanced, low-cost silicon materials made it possible to produce affordable silicon cells. Government subsidies have also contributed to decreasing the overall cost. Customers must contact the manufacturers to find the exact price before making a purchase. The cost of a silicon solar cell can alter based on the number of cells used and the brand Costs 32
  33. 33. Applications. 33
  34. 34. ● Automotive industry ● Charging calculators ● Household appliances ● Power Farms for producing electricity on large scale ● Business-related industries Applications 34
  35. 35. References. [1] Saga, T. Advances in crystalline silicon solar cell technology for industrial mass production. NPG Asia Mater 2, 96–102 (2010). [2] Sopian, K., et al. “An Overview of Crystalline Silicon Solar Cell Technology: Past, Present, and Future.” AIP Conference Proceedings, vol. 1877, no. 1, Sept. 2017, p. [3] Battaglia, Corsin, et al. “High-Efficiency Crystalline Silicon Solar Cells: Status and Perspectives.” Energy & Environmental Science, vol. 9, no. 5, May 2016, pp. 1552– 76 35
  36. 36. Thank You. 36

Editor's Notes

  • Back contact acts as emitter zone
  • The Czochralski process (Cz) is also known as “crystal pulling” or “pulling from the melt”. In this process, Silicon (Si) is first melted and then allowed to freeze into a crystalline state in a controlled manner. The advantage of this method is that it is fast and highly controllable. The industrial cultivation of high-purity monocrystalline Silicon crystals using the Cz Process has become well established primarily for the solar and semiconductor industries (in the computer industry for integrated circuits and in microsystem technology). You benefit from the high effectiveness and quality of the cultivated crystals.

    To begin with, high-purity polycrystalline silicon is placed in the Silica crucible of a single crystal pulling system and then melted in a controlled atmosphere (Argon) using a resistance heater. Once the temperature of the melt has stabilized (the melting point is around 1,412 °C), a rotating monocrystalline Silicon seed crystal is dipped into the melt. A slight temperature drop initiates the crystallization of Silicon on the seed crystal. When the seed crystal is slowly pulled upward, a cylindrical Silicon monocrystal hanging on the seed crystal starts to form. The pulling rate and temperature are regulated such that a Silicon monocrystal—whose orientation and structure is identical to those of the seed crystal—can be pulled with a constant diameter.

  • The Siemens process involves deposition of silicon from a mixture of purified silane or trichlorosilane (TCS) gas with an excess of hydrogen onto high-purity polysilicon filaments. The silicon growth then occurs inside an insulated reaction chamber or ’bell jar’, which contains the gases. The filaments are assembled as electric circuits in series and are heated to the vapor deposition temperature by an external direct current. The silicon filaments are heated to very high temperatures of 1100–1175 ºC at which TCS with the help of the hydrogen decomposes to elemental silicon and deposits as a thin-layer film onto the filaments. Hydrogen chloride (HCl) is formed as a by-product.
    The most critical process parameter is temperature control. The temperature of the gas and filaments must be high enough for the silicon from the gas to deposit onto the solid surface of the filament, but well below the melting point of 1414 ºC, so that the filaments do not start to melt. Second, the deposition rate must be well controlled and not too fast because otherwise the silicon will not deposit in a uniform, polycrystalline manner, making the material unsuitable for semiconductor and solar applications.
  • However, converting sand into high grade silicon comes at a high cost and is an energy intensive process. High-purity silicon is produced from quartz sand in an arc furnace at very high temperatures.

    Ingots: The silicon is collected, usually in the form of solid rocks. Hundreds of these rocks are being melted together at very high temperatures in order to form ingots in the shape of a cylinder. To reach the desired shape, a steel, cylindrical furnace is used.  
    In the process of melting, attention is given so that all atoms are perfectly aligned in the desired structure and orientation. Boron is added to the process, which will give the silicone positive electrical polarity.
    Mono crystalline cells are manufactured from a single crystal of silicon. Mono Silicon has higher efficiency in converting solar energy into electricity, therefore the price of monocrystalline panels is higher.
    Polysilicone cells are made from melting several silicon crystals together. You can recognise them by the shattered glass look given by the different silicon crystals. After the ingot has cooled down, grinding and polishing are being performed, leaving the ingot with flat sides

    Wafers: Wafers represent the next step in the manufacturing process.
    The silicon ingot is sliced into thin disks, also called wafers. A wire saw is used for precision cutting. The thinness of the wafer is similar to that of a piece of paper.
    Because pure silicon is shiny, it can reflect the sunlight. To reduce the amount of sunlight lost, an anti-reflective coating is put on the silicon wafer.

    Solar Cell: The following processes will convert a wafer into a solar cell capable of converting solar power into electricity.
    Each of the wafers is being treated and metal conductors are added on each surface. The conductors give the wafer a grid-like matrix on the surface. This will ensure the conversion of solar energy into electricity. The coating will facilitate the absorption of sunlight, rather than reflecting it.

    System+ Battery+ Inverter: The solar cells are soldered together, using metal connectors to link the cells. Solar panels are made of solar cells integrated together in a matrix-like structure.
    The current standard offering in the market are:
    48 cell panels - suitable for small residential roofs.
    60-cell panels - this is the standard size.
    72-cell panels -used for large-scale installations.

  • With the invention of modern photovoltaics, and in a quest to increase efficiencies and reduce costs, engineers in the 1970s demonstrated that concentrating sunlight and focusing the equivalent of hundreds of “suns” onto solar cells increases their efficiency (Backus, 2003). For example, 20.7% efficient mono-c-Si cells, under AM1.5 spectral conditions, reach 26.5% efficiencies under 500 suns because the efficiency of a solar cell increases as the voltage- and fill factor of the cell rise. However, further increases in solar concentration require augmented cell package designs to collect the increased electrical current and dissipate additional waste heat. Otherwise there will be a decline in efficiency as shown in Fig. 1 for a cell package optimized for 500 suns.

    Unlike the flat-plate photovoltaic systems seen on roofs, solar concentrators must track the sun to focus light on to a solar cell throughout the day. Sun tracking increases the daily energy production above that of non-tracking flat-plate PV panels. However, electrical output drops dramatically if the sun is not focused on the cell, or if clouds block the sun.
  • kerf is silicon dust that is wasted when silicon ingots are cut into thin wafers