应用光伏学题库Word文档格式.docx

1、6. Research and development of photovoltaics received its first major boost from the space industry in the 1960s.11. A photon is characterized by either a wavelength, denoted by , or equivalently an energy, denoted by E.2. There is an inverse relationship between the energy of a photon （E） and the w

2、avelength of the light （） given by the equation: ，.3. The photon flux is defined as the number of photons per second per unit area.4. The total power density emitted from a light source can be calculated by integrating the spectral irradiance over all wavelengths or energies of interest.5. In the an

3、alysis of solar cells, the photon flux is often needed as well as the spectral irradiance.6. The blackbody sources which are of interest to photovoltaics, emit light in the visible region. 7. The spectral irradiance from a blackbody is given by Planks radiation law.8. The peak wavelength of the spec

4、tral irradiance is determined by differentiating the spectral irradiance and solving the derivative when it equals 0. The result is known as Wiens Law:9. Solar radiation in space:. Hsun=5.961107W/m2.10. The solar radiation outside the earths atmosphere have been defined as a standard value called ai

5、r mass zero （AM0） and takes a value of 1.353 kW/m2.11. The spectral irradiance from a blackbody at 6000 K （at the same apparent diameter as the sun when viewed from earth）; from the suns photosphere as observed just outside earths atmosphere （AM0）; and from the suns photosphere after having passed t

6、hrough 1.5 times the thickness of earths atmosphere （AM1.5G）.12. The Air Mass is defined as:,. where is the angle from the vertical （zenith angle）.13. When the sun is directly overhead, the Air Mass is 1.14. The standard spectrum at the Earths surface is called AM1.5G （the G stands for global and in

7、cludes both direct and diffuse radiation） or AM1.5D （which includes direct radiation only）, these calculations give approximately 970 W/m2 for AM1.5G。15. The standard AM1.5G spectrum has been normalized to give 1 kW/m2 due to the convenience of the round number and the fact that there are inherently

8、 variations in incident solar radiation.16. The standard spectrum outside the Earths atmosphere is called AM0, because at no stage does the light pass through the atmosphere. 17. The standard AM0 spectrum is typically used to predict the expected performance of cells in space.18. Wavelengths below 0

9、.3 m are strongly absorbed by ozone. The absorption bands around 1 m are produced by water vapor absorption, complemented by CO2 absorption at longer wavelengths. 19. The air mass represents the proportion of atmosphere that the light must pass through before striking the Earth relative to its overh

10、ead pathlength.20. Diffuse radiation is predominantly at the blue end of the spectrum because of more effective scattering at small wavelengths. Hence, the sky appears blue.21. AM1 radiation （radiation when the sun is directly overhead）, has a diffuse component of about 10% when skies are clear.22.

11、Carbon dioxide absorbs strongly in the 13-19 m wavelength band and water vapour, another atmospheric gas, absorbs strongly in the 4-7 m wavelength band. Most outgoing radiation （70%） escapes in the “window” between 7-13 m.23. The two common methods which characterize solar radiation are the solar ra

12、diance （or radiation） and solar insolation.24. While solar irradiance is most commonly measured, a more common form of radiation data used in system design is the solar insolation.25. The solar radiance is an instantaneous power density in units of kW/m2.26. The solar insolation is the total amount

13、of solar energy received at a particular location during a specified time period, often in units of kWh/（m2 day）, also in units of MJ/m2 per year.27. The average daily solar insolation in units of kWh/m2 per day is sometimes referred to as “peak sun hours”. For example, a location that receives 8 kW

14、h/m2 per day can be said to have received 8 hours of sun per day at 1 kW/m2.28. The declination of the sun is the angle between the equator and a line drawn from the centre of the earth to the centre of the sun. 29. The declination of the sun is zero at the equinoxes （March 22 and September 22）, pos

15、itive during the northern hemisphere summer and negative during the northern hemisphere winter.30. The elevation or altitude angle is the angular height of the sun in the sky measured from the horizontal. The elevation is 0 at sunrise and 90 when the sun is directly overhead.31. The zenith angle is

16、similar to the elevation angle but it is measured from the vertical rather than from the horizontal.32. The azimuth angle is the compass direction from which the sunlight is coming with North = 0, South = 180, 90 at sunrise and 270 at sunset. 33. For a fixed tilt angle, the maximum power over the co

17、urse of a year is obtained when the tilt angle is equal to the latitude of the location.34. The module is orientated to the equator so it faces north in the southern hemisphere and south in the northern hemisphere.35. The sun is at an altitude of 30 to the horizontal, the corresponding air mass is 2

18、 .36. The length of the shadow cast by a vertical post with a height of 1 m under AM1.5 illumination is .21. The most important parameters of a semiconductor material for solar cell operation are: （1） the band gap; （2）the number of free carriers available for conduction; （3）the generation and recomb

19、ination of free carriers in response to light shining on the material.2. The electrical properties of semiconductors can be explained using two models, the bond and the band models.3. The band model describes semiconductor behavior in terms of the energy level between valence and conduction bands.4.

20、 The lower energy level of a semiconductor is called the valence band （EV） and the energy level at which an electron can be considered free is called the conduction band （EC）. The band gap （EG） is the distance between the conduction band and valence band.5. The band gap corresponds to the minimum en

21、ergy needed to release an electron from a valence bond to the conduction band where it can conduct a current.6. Both the electron and hole can participate in conduction and are called carriers7. It is possible to shift the balance of electrons and holes in a silicon crystal lattice by doping it with

22、 other atoms. 8. Atoms with one more valence electron than silicon are used to produce n-type semiconductor material, which adds electrons to the conduction band and hence increases the number of electrons. 9. In p-type material, the number of electrons trapped in bonds is higher, thus effectively i

23、ncreasing the number of holes. 10. In doped material, there is always more of one type of carrier than the other and the type of carrier with the higher concentration is called a majority carrier, while the lower concentration carrier is called a minority carrier11. The number of carriers in the con

24、duction and valence band with no externally applied bias is called the intrinsic carrier concentration.12. For majority carriers, the equilibrium carrier concentration is equal to the intrinsic carrier concentration plus the number of free carriers added by doping the semiconductor.13. Silicon or ot

25、her semiconductor materials used for solar cells can be single crystalline, multicrystalline, polycrystalline or amorphous.14. Terminology for various types of crystalline silicon （c-Si）Descriptor Symbol Grain Size Common Growth Techniques Single crystal sc-Si10cmCzochralski （CZ） float zone （FZ） Mul

26、ticrystalline mc-Si1mm-10cmCast, sheet, ribbon Polycrystalline pc-Si1m-1mmChemical-vapor deposition Microcrystalline c-Si1mPlasma deposition 15. It has been found that the incorporation of atomic hydrogen in amorphous silicon, to a level of 510%, saturates the dangling bonds and improves the quality

27、 of the material.16. The minority carrier diffusion lengths in the silicon-hydrogen alloys （a-Si:H） are much less than 1 m.17. Photons incident on the surface of a semiconductor will be either reflected from the top surface, will be absorbed in the material or, failing either of the above two proces

28、ses, will be transmitted through the material.18. For photovoltaic devices, reflection and transmission are typically considered loss mechanisms as photons which are not absorbed do not generate power.19. If the photon is absorbed it will raise an electron from the valence band to the conduction ban

29、d.20. The absorption depth is a useful parameter which gives the distance into the material at which the light drops to about 36% of its original intensity, or alternately has dropped by a factor of 1/e.21. Neglecting reflection, the amount of light which is absorbed by a material depends on the absorption coefficient and the thickness of the absorbing material.22. Assuming that the loss in light intensity （i.e., the absorption of photons） directly causes the generation of a