untitled

Transcription

1 The Earth - Our Energy Challenge 綠 -- 立 March 5, 2010 Energy Challenge of World 量 (Barrel) 43 年 量 146 立 62 年 量 年 量 9, 年 20 不 都 度 20 年 了 年 都 CO2 量 (2005/2/16 ) 例 12%~15% World Energy Millions of Barrels per Day (Oil Equivalent) Source: John F. Bookout (President of Shell USA), Two Centuries of Fossil Fuel Energy International Geological Congress, Washington DC; July 10,1985. Episodes, vol 12, (1989). Energy Challenge of Taiwan 98 力 識 不 不 例 2010 年 量 :513.9 力 :215.9 力 :216.8 :2.1:5.0 :74.1 Increasing CO 2 Emissions A rise in Atmospheric CO 2 Global Temperature 1

2 North Pole 都 來 ( ) 力 力 1 量 (~ J) 類 1 年 (2005) 50 年 Sunlight 165,000 TW of sunlight hit the Earth every day 1.33 TW needed by people on the Earth every day (Photovoltaic) (Solar Cell) 流 料 年 ( --) 量 度 力 不 ( 聯 ) 輻 (BIPV) 類 Single Crystalline :12~20% III What are semiconductors IV V Elemental Semiconductors Si, Ge Solar Cells Compound Nano & Organic Crystalline Amorphous Thin Film (Si:H, SiGe, SiC..) Single Crystalline (GaAs, InP..) Poly Crystalline (CdS, CdTe, CuInSe 2...) Poly Crystalline Thin Film Poly. : 6~8% :10~18% : % ( PV ) TiO 2 / 料 B Al Ga In C Si Ge Sn N P As Sb Binary Compounds GaAs, InP, GaSb, GaN, InAs, AlAs, AlP Ternary Compounds AlGaAs, InGaAs, InGaP, AlGaP, InAlAs, GaAsSb Quarternary Compounds InGaAsP, AlGaAsP, InAlGaAs, AlInGaP 2

3 Name Symbal Si Atomic number 14 Atomic weight Discoverer Jöns Jacob Berzelius Discovered at Sweden Discovery date 1824 Origin of name From the Latin word "silicis" meaning "flint" Bond length in single crystal Si Å Density of solid 2.33 g/cm 3 Molar volume cm 3 Velocity of sound 2200 m/sec Electrical resistivity 100,000 μω cm Reflectivity 28% Melting point 1414 C Boiling point 2900 C Amorphous Polycrystalline Single Crystal From Sand to Wafer From Sand to Wafer (cont.) Quartz sand: silicon dioxide Sand to metallic grade silicon (MGS) React MGS powder with HCl to form TCS Purify TCS by vaporization and condensation React TCS to H 2 to form polysilicon (EGS) Melt EGS and pull single crystal ingot Cut end, polish side, and make notch or flat Saw ingot into wafers Edge rounding, lap, wet etch, and CMP Laser scribe Epitaxy deposition Polysilicon Deposition, EGS Purification II Heat (1100 C) SiHCl 3 + H 2 Si + 3HCl TCS Hydrogen EGS Hydrochloride H 2 Liquid TCS Process Chamber H 2 and TCS TCS+H 2 EGS+HCl EGS Carrier gas bubbles 3

4 Electronic Grade Growth of Crystal Pulling: CZ method CZ Crystal Pullers Single Crystal Seed Quartz Crucible Single Crystal silicon Ingot Molten 1415 C Heating Coils Graphite Crucible Mitsubish Materials Source: CZ Crystal Pulling Floating Zone Method Heating Coils Movement Poly Si Rod Molten Heating Coils Single Crystal Source: Seed Crystal 4

5 Comparison of the Two Methods CZ method is more popular Cheaper Larger wafer size (300 mm in production) Reusable materials Floating Zone Pure silicon crystal (no crucible) More expensive, smaller wafer size (150 mm) Mainly for power devices. A silicon ingot is a single crystal of Si. Within the bulk of the crystal, the atoms are arranged on a well-defined periodical lattice. The crystal structure is that of diamond. (cont.) Ingot Left: crystal ingots grown by the Czochralski crystal drawers in the background Right: 200 mm and 300 mm Si 300-mm (12-inch) Si Ingot 400-mm (16-inch) Si Ingot Wafers Evolution of Wafer Size mm (8-inch) Si Wafers 400-mm (16-inch) Si Wafers mm 100 mm 125 mm 150 mm 200 mm 300 mm 5

6 理 Substrate P-N Diode Antireflection Texturing Metal Contact 洞 (hole) (electron) - Electrode Anti-Refection Coating n n-type Semiconductor p p-type Semiconductor Electrode + 流 Electric Current P N 料 量 料 離 ( - 洞 ) - 洞 (Hole) - (Electron) (P ) (N ) 流流 ( 亮 ) P-N Juction Built-in Potential ρ(x) qn D -x p 0 x n x -qn A (x) -x p x n - m Ψ i (x n )-Ψ i (-x p ) x -x p x n V bi x P Energy Band N Principle E c E c E f E i E i E f (p-type) p E v (n-type) n E v qψ Fp qv bi qψ Fn E c E f E i E v 6

7 Biased Operation Photovoltaic Effect of P-N Junction Ways to Reduce Optical Losses Minimize top contact coverage area of the cell (although this may result in increased series resistance). Use anti-reflection (AR) coatings on the top of the cell. Texturing the surface of the Thicker solar cell to increase optical absorption (also need matching diffusion length) The optical path length in the solar cell may be increased by a combination of surface texturing and light trapping. Different Front Metal Patterns Anti-Reflection Coatings Textured Surface to Decrease Reflection loss on the Top 7

8 Surface Texturing Photocurrent vs Cell thickness Scanning electron microscope photograph of a textured silicon surface Light Trapping in Solar Cell by Total Internal Reflection Lambertian Back Reflector (Back Surface Texturing) Lambertian back reflector randomizes the direction of the reflected light. Light absorption can be dramatically increased by a factor up to 4n 2 This allows an optical path length of approximately 50 times the physical devices thickness EVA 0.125" 0.015" 例 例 Cells 0.014"EVA Tedlar TM (Dupont) 例 0.015" " 0.1~1" EVA 0.015" Cells 0.014" EVA 0.015" 0.1~1" EVA (ethylene-vinyl-acetate) ( ) 8

9 路 Building-Integrated Photovoltaic (BIPV) System 蘭 Floriade Exhibition Hall BIPV 利 料 降 度 見度 PV 量 2.3 MWp (3 ) DB Lehrter Station, Berlin BIPV NASA Helios PV 量 325 kwp (2003) 3,311 m 2 Flabeg Solar 1, ,000 BP LGBG 123x123 mm η =17% 料來 行 度 5-7 ( 錄 96,000 ) 60 mph ( 25 mph) 247 ( ) 量 2,000 率 >22% 9