Solar Photovoltaic Technologies

Transcription

1 Solar Photovoltaic Technologies Lecture-29 Prof. C.S. Solanki Energy Systems Engineering IIT Bombay

2 Contents Brief summary of the previous lecture Production of Si MG-Si, EG-Si Siemens Process, FBR process CZ Si, FZ Si Wafer dicing 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-2

3 Semiconductor Fundamentals, P-N Junction, Solar cell Physics, Solar cell design Solar PV Technologies Production of Si Wafer based Si solar cells Thin-film solar cells 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-3

4 Contents- Production of Si Solar PV Chain Why Si for PV? Demand for Si feedstock Si wafer production process EG poly-si (Siemens type, FBR) CZ & FZ process of ingot production wafer dicing Si feedstock from various sources Multi-crystalline Si wafers and ribbon Si 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-4

5 Si for PV Solar energy (PV) is a very fast growing market where the basic technology depends on availability of pure Si. This material is today in high demand and a shortage is expected. Most analysts assume that silicon will remain the dominant PV material for at least a decade. One of Shell s energy scenario indicates that solar energy will be the single largest energy source within Solar PV would play important role in it 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-5

6 Why Silicon? At the time being it is almost the only material used for solar cell mass production Easily found in nature, Silicon oxide forms 1/3 of the Earth's crust It is non-poisonous, environment friendly, its waste does not represent any problems It is fairly easy formed into mono-crystalline form Its electrical properties with endurance of 125 C Si is produced with % purity in large quantities. 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-6

7 Solar PV market Worldwide production of Solar PV modules Solar PV industry has recorded a growth of 30% in the last decade Crossing the GW-level: Last year alone worldwide solar cell production reached 1,256 MW (in 2004), 67 percent increase over the 750 MW output in /1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-7

8 Contribution of Si in PV market Others include CdTe, CIGS, C-Si/a-Si (4.5%) Over 90% of solar cell are made of Si 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-8

9 Companies producing Si Si Wafer Manufacturers Hemlock (USA) SEH, SUMCO Wacker Chemie (Germany) Tokuyama Soda (Japan) ASiMi (USA) MEMC Electronic Material Inc., (USA) Dedicated manufacturers for PV (wafers and cells) Kyocera (Japan), BP Solar (USA), Shell Solar (USA), Photowatt (France). RWE Schott (USA/Germany) 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-9

10 Crystal type Single crystal Si wafers Multi-crystal Si Wafers Wafers for solar cells Shape Circular Pseudo square Square 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-10

11 ingot Lecture-29 Si Wafer Production High temp, Carbon Silica HCl MGS (s) Chlorosil -anes (g) Separation and purification top Pure silanes (g) Wafer producti on tail Single crystal growth CVD, Solid silicon(s) 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-11

12 Solar PV Chain There are several steps from raw material to power systems Silica MG-Si Purification Casting Surface treatment Cell assembly 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-12

13 Contents-Si production Solar PV Chain Why Si for PV? Demand for Si feedstock Si wafer production process MG-Si EG poly-si (Siemens type, FBR) CZ & FZ process of ingot production wafer dicing Si feedstock from various sources Multi-crystalline Si wafers and ribbon Si 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-13

14 Metallurgical grade (MG) Si MG-Si is material with 98-99% purity, Produced in about 1 Million tons per year Produced in countries which cheap electricity and quartz deposits (USA, Europe, Brazil, Australia, Norway) Average price is 2 to 4 $/kg MG-Si is produced by reduction of SiO 2 with C in arc furnace at 1800 o C. SiO 2 + C Si + CO 2 Application in producing chlorosilane for electronic grade Si production, production of Al and Steel Typical impurities are iron, aluminium, calcium and magnesium 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-14

15 Silane and Chlorosilane for Prime Poly Electronic grade (EG-Si), 1 ppb Impurities, % MG-Si EG-Si: impurities reduction by five order of magnitude is required convert MG-Si to gaseous chlorosilanes or silane, purified by distillation For instance Trichlorosilane SiHCl 3 and silane SiH 4 On chlorination of MG-Si Si + 2Cl SiCl 4 The following reactions result in tri-chlorine-silane gas: SiCl 4 + HCl SiHCl 3 The following reactions result in silane gas 4 SiHCl 3 SiH SiCl H 2 SiF 4 + NaAlH SiH 4 + NaAlF 4 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-15 Si

16 Siemens type reactor Waste gases Boiling point.: +32 C SiHCl 3 +H 2 Quartz bell Jar Polysili con depositi on Power supply Generate by-products containing chlorine -Pure SiHCl 3 in Gas Phase Pure Si in Solid Phase SiHCl 3 + H 2 Si + 3HCl Chemical Vapor Deposition (CVD) process Siemens type reactor Deposition process is slow 10 days/ton using 12 Siemens reactors Wacker, Hemlock, Mitsubishi, Tokuyama, Sumitomo SiTiX, MEMC Italia 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-16

17 Fluidized bed reactor (BFR) Gran ular Si Silicon seed particles are held in suspension by a gas mixture (H 2 and SiH 4 ) At 600 C gas phase decomposition takes place, causing the seed particles to grow up to 2 mm in size Big particles falls due to weight SiH 4 Si is collected from the bottom of the jar Continuous process considerably higher production rates and lower energy consumption Yielding silicon of the highest purity 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-17

18 Czochralski (CZ) process: (CZ Si wafer) Seed Holder Poly-EGS is melted in a quartz crucible (SiO 2 ) Seed Seed particle introduced to begin crystallization Crystal neck Seed pulled to generate desired wafer diameter Si melt Shoulder Ingot is cooled Crucible is discarded Air + SiO 2 +Co Air + SiO 2 +Co Thermal shield (warping and cracking) 8/1/2008 IIT Bombay, C.S. Solanki Solar Photovoltaic Technologies L29-18