15. Cost goals for third generation solar cells Efficiency and cost projections for first-, second- and third generation photovoltaic technology (wafers, thin-films, and advanced thin-films, respectively) Source: University of New South Wales
21. The PV Value Chain (multi-crystalline) Polysilicon Wafer Solar Cell Solar Module Chemical Process (purification) Casting Cutting Surface Treatment Assembly Systems Installation Operation
23. How does solar energy work? Solar Electric or Photovoltaic Systems convert some of the energy in sunlight directly into electricity. Photovoltaic (PV) cells are made primarily of silicon, the second most abundant element in the earth's crust, and the same semiconductor material used for computers. When the silicon is combined with one or more other materials, it exhibits unique electrical properties in the presence of sunlight. Electrons are excited by the light and move through the silicon. This is known as the photovoltaic effect and results in direct current (DC) electricity. PV modules have no moving parts, are virtually maintenance-free, and have a working life of 20 - 30 years . Silicon Solar cell
24. Photovoltaics Most current solar cells are photovoltaic Typically made from silicon or amorphous silicon. Typical efficiency ~ 12%. Best efficiency ever in laboratory: ~30%. Theoretical maximum, including concentrating light: 43% Generic design: doped pn junction. Photons come in and photoionize donors. Built-in electric field at junction causes carriers to flow, building up a potential (voltage) btw the p and n sides. Clearly one can play with different band gap systems to arrive at materials with different absorption spectra. Also, good mobility of charge essential for this to work well - trapping of charge or poor mobility will kill efficiency.
25. Principle p-n Junction Diode. Silicon Solar cell Ref. Soft Condensed Matter physics group in univ. of Queenland
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28. Poly-Si Solar cell Making process 기판준비 : Si ingot 330 m 2cm x 2cm Surface cleaning Texturing : chemical v-groove p-n junction : POCl 3 (900 ºC ) ITO increasing minorty carrier correction, ARC
29. Back Surface Field Deposition Al and Ag ohmic-contact Forward surface Electrode Anti-reflection coating (ARC) TiO 2 deposition
30. H 2 diffusion dangling bond H2 bonding Decreasing recombination Measure H 2 H 2 H 2 H 2
31. - An individual PV cell typically produces between 1 and 2 watts Solar Cell, Module, Array
