TW201300745A - Method for deriving estimated spectrum of light source to be determined - Google Patents

Abstract

A method of deriving an estimated spectrum of a light source to be determined is disclosed. Firstly, a desired wavelength range, from λ a to λ b, is divided into several wavelength-bands. Next a plurality of solar cells, each having different antireflective films in thickness or different internal quantum efficiency, is prepared in accordance with the number of the wavelength-bands. Thereafter, the reflectivity, and the internal quantum efficiency of each solar cell at each wavelength-band are measured. Thereafter, the light source to be determined is used to irradiate the solar cells, and then the output currents of each solar cell are measured. Next, every equation, which is the measured output current of each solar cell is proportional to the sum of the product of the anti-reflectivity, the internal quantum efficiency, and the average photon flux of each solar cell in different wavelength-band, is listed, and the unknown average photon fluxes in different wavelength-band can be calculated by solving these simultaneous equations. Finally, the approximately spectrum can be draw according to the relationship of the average photon flux versus the wavelength-band.

Description

Method for obtaining an approximate spectrum of a light source to be tested

The invention relates to a spectroscopic analysis method for a light source to be tested, in particular to a spectral analysis of a light source to be tested by using a plurality of solar cells without using a spectrometer, and the thickness of the antireflection film contained therein is different.

In recent years, various environmental factors such as air pollution and fuel shortage of petrochemical power generation, waste pollution of nuclear power plants, and environmental damage of hydropower generation are testing the current mainstream power generation methods, and sustainable alternative energy research has received high attention. Solar energy is one of the most promising alternative energy sources. Because the energy of the sun's surface has far exceeded the energy we use, how to use it effectively is one of the important topics in the coming decades.

The power generation efficiency of solar cells and the efficiency of energy conversion determine whether solar energy can completely replace existing petrochemical energy in the future as a main source of power. Therefore, after each batch of solar cells completes the process, the finished product will be tested for energy conversion efficiency before leaving the factory, that is, the current that the solar cell can output under illumination, and classified according to this. However, due to the uncertainty of the weather, the standard of grading is to use a standard light source to replace the sunlight with a predetermined light intensity, and to illuminate the solar cell, and then measure its output current, according to the current size. The so-called standard light source is a light source whose spectrum is close to the solar spectrum, that is, an analog light source.

Therefore, analog light sources are a very important key to testing solar cells. The difference between the spectrum of the simulated source and the actual solar spectrum has a large impact on the determination of solar cell performance. Figure 1 shows a comparison of the simulated spectrum with the solar spectrum at a light intensity of 1000 W/m ² . As shown in Figure 1, curve 10 is the solar spectrum and curve 11 is the solar spectrum. The two spectra are roughly similar. However, the simulated spectrum is distributed in the wavelength range of 800~1000 nm, which is much larger than the actual solar spectrum. Therefore, if a group of solar cells are unfortunately capable of absorbing photons in this wavelength range, this will be This results in distortion of the measured conversion efficiency. Therefore, in order to make the test results of the solar cells conform to the facts, the correction of the analog light source is very important.

Moreover, even if the analog light source is taken from a manufacturer with reliable quality and is precisely calibrated, it does not guarantee that it will retain the same quality as the factory after a period of use. Therefore, it needs to be corrected regularly, or it can be replaced within the recommended period of the manufacturer that provides the analog light source.

The calibration method that can be thought of in the past is to use a spectrometer to make actual measurements for sunlight and analog light sources, and then calculate the difference between the two spectra in each band based on the measurement results. Spectrometers use complex optical designs that typically use dispersive elements to spatially distribute the path according to the wavelength of the incident light.

The general way of correcting efficiency in the industry is to regularly send solar cells to the Fraunhofer Solar System Research Institute (ISE) in Germany, and then adjust the intensity of the analog light source based on this to ensure accurate measurement of solar cell conversion efficiency. Sex. It takes nearly three to six months to send a standard film back and forth, which is quite time consuming.

At the measuring machine end, the intensity of the simulated light source is measured using a standard piece (approximately 5 × 5 cm ² ) and the measured results are fed back to the measured efficiency. For example, if the intensity of the light source measured by the standard piece is 1050 W/m ^{2 during the} test, the current measured by the battery piece is automatically corrected by 0.5%. If a part of the surface of the standard sheet is covered with debris that is dropped or contaminated, the standard sheet will be inaccurate (in the above case, the original area of the standard sheet will be small and the magnification error will be increased), which will result in waiting. The solar cell measurement results are incorrect, but the errors caused by this cause are often not easily noticeable.

Therefore, in order to avoid the measurement efficiency deviation caused by the measurement spectral shift, a method for analyzing the spectrum of the analog light source without using a spectrometer is provided, and the light intensity monitoring and correction of different wavelengths of the analog light source are performed by comparing the solar spectrum. For the purpose of the present invention.

In view of the above problems, the present invention provides a method for obtaining an approximate spectrum of a light source to be tested, comprising: dividing a wavelength range λ _a to λ _{b of} an approximate spectrum into n bands; providing the same number according to the number of bands divided Solar cell N, wherein each solar cell has an anti-reflection film layer or internal quantum efficiency of different thicknesses; respectively, the internal quantum efficiency IQE _{Nn of} each of the solar cells at each wavelength is measured; respectively, the solar energy is measured An average reflectance R _{Nn of the} battery at each of the wavelength bands; the solar cells are irradiated with the light source to be measured to measure the output current I _N , wherein the light intensity of the light source to be tested is a predetermined value; The average photon flux Φ _n of the solar cells at the bands, the average anti-reflectance (1-R _Nn ) at the bands, the internal quantum efficiency IQE _Nn and the output current I _N at the bands relation of the equation, the equation is the relationship between the output current I _N is proportional to the average photon flux Φ _n in the plurality of band antireflective average rate (1-R _Nn) of the plurality of the band, the lower band of the plurality of IQE _Nn quantum efficiency of the product and, wherein the average photon flux Φ _n in the plurality of bands is unknown; simultaneous equations above relationship, the plurality of unknowns and solving Φ _n; and based on the average photon in the plurality of band-pass The quantity Φ _n plots the approximate spectrum of the light source to be tested relative to the bands.

The method of the present invention can be used to detect and correct solar light analog sources. Furthermore, the difference between the average light intensity of the simulated light source and a solar spectrum in different bands is compared, and whether the difference exceeds an error tolerance range is determined, and if so, the solar light analog light source exceeds the error tolerance range. The band is used for intensity correction.

The method of the present invention is not only simple, but also allows the solar energy industry to adjust and correct the solar light source at almost no cost.

In order to make the above objects, features and advantages of the present invention more comprehensible, the method for obtaining an approximate spectrum of a light source to be tested according to the present invention will be described in detail with reference to the accompanying drawings. as follows.

The invention utilizes the thickness of the anti-reflection film layer of the solar cell to affect the characteristics of the light energy absorption band, that is, when the anti-reflection film is thicker, the absorption capacity for long-wavelength photons (low anti-reflection rate) is better than the short-wavelength ( The antireflection rate is high. On the contrary, when the antireflection film is thinner, the absorption capacity of short-wavelength photons is better, and a plurality of solar cells having different thicknesses of the anti-reflection film are prepared.

Subsequently, a spectrum band is divided into a plurality of bands, and a light source with a known spectrum is used to generate a plurality of color lights by a beam splitter, the photon fluxes of the color lights are known), and the solar cells are respectively analyzed under the bands The average reflectance R and the average internal quantum efficiency IQE are such that the reflectance R and the internal quantum efficiency IQE at these bands become known. Then, the solar cells are illuminated by the light source to be tested (the spectrum is unknown). The equation is listed by the ratio of the photon flux Φ (unknown) at each band to the anti-reflectance (1-R) of the above band and the internal quantum efficiency (IQE) of the band proportional to the output current.

Then, according to the equation of each solar cell in each band, the matrix equation can be obtained. The approximate spectrum of the light source to be measured can be obtained by solving the photon flux Φ at each band in the matrix equation. The detailed steps and description are as follows: The detailed flow of the embodiment of the present invention is shown in FIG. 2. First, the wavelength ranges λ _a to λ _{b of the} approximate spectrum to be obtained are divided into n bands, as by step S200. In the embodiment of the present invention, the light source to be tested is a solar light source, λ _a = 300 nm, λ _b = 1200 nm, and the preferred embodiments λ _a to λ _b are 400 nm and 1100 nm, respectively, and the range is at least divided into 6 Band.

According to the number of divided bands, the same number of solar cells N are provided, each of which has an anti-reflection film layer or internal quantum efficiency of a different thickness, as by step S205. In this embodiment, the thickness distribution of the anti-reflection film layer of the solar cell is such that the lowest average reflectance of the solar cells falls at different positions of the bands. Please see the table below:

The use of solar cells is only one embodiment of the invention, and other photoelectric conversion devices, such as photon detectors, can also be used. In the embodiment of the present invention, six solar cells are used corresponding to the number of divided bands, and the thickness of the anti-reflection film of each solar cell is 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100, respectively. Nm.

The internal quantum efficiency (IQE _Nn ) of the solar cell at each band is separately measured, as by step S210. In an embodiment of the invention, the solar cells have the same internal quantum efficiency for the same wavelength band.

The average reflectance (R _Nn ) of the solar cell at each wavelength band is separately measured, as by step S215. In the embodiment of the present invention, when measuring the internal quantum efficiency and the reflectivity, there is a full-band light source in the machine, and the reflectivity and current of the solar cell in each band are measured. Since the intensity of the light source used for measurement is known, the internal quantum efficiency can be derived.

Next, the photoelectric conversion device is irradiated with the light source to be tested to obtain an output current I _N as by step S220. Wherein, the light intensity of the light source to be tested is in a predetermined range of values, and is one of 100 to 3000 W/m ² .

The average photon flux Φ _{n of} each solar cell at the bands, the average anti-reflectance (1-R _Nn ) at the bands, the internal quantum efficiency IQE _n and the output current I at each of the bands are listed separately. The relational equation of _N. Please note that the first subscript N represents the Nth solar cell, for example: the first piece of solar energy, in one embodiment, has a thickness of 50 nm. The second subscript n represents the band. The relational equation is that the output current I _{N is} proportional to the product of the average photon flux Φ _n in the bands, the average antireflection rate (1-R _Nn ) in the bands, and the internal quantum efficiency IQE _{Nn in} the bands. ,As follows:

Among them, the average photon flux Φ _n of each band is an unknown number.

Finally, the above relationship equations are linked, and the unknowns are solved, as in step S225. The above-mentioned simultaneous equations are expressed in matrix form as follows:

In the embodiment of the present invention, the selected solar cell only changes the reflectivity, but in the same wavelength band, the internal quantum efficiency of the solar cell is equal, that is, IQE ₁₁ =IQE ₂₁ =...=IQE ₆₁ ; IQE ₁₂ =IQE ₂₂ =...=IQE ₆₂ ;...IQE ₁₆ =IQE ₂₆ =...=IQE ₆₆ .

In another embodiment, the internal quantum efficiency can also be changed by selecting a solar cell made of a wafer cut at different positions of the ingot, but controlling the thickness of the anti-reflection layer to make the anti-reflection rate (1-R) _Nn ) is equal. By solving the matrix, the average photon flux Φ ₁ ~ Φ _n for each band can be calculated.

Finally, according to the average photon flux Φ ₁ ~ Φ _n of each band with respect to the wavelength, the approximate spectrum of the light source to be tested can be drawn, as in step S230.

The embodiment of the present invention is applied to correct the difference in intensity between the light source to be tested and the solar spectrum in different wavelength bands, and further includes the following steps. First, by the relationship between the average photon flux Φ _n and the average light intensity E _n , Φ _n =E _n /(h×c/λ _n ), the average light intensity E _{n of} each band can be calculated, as in step S235. . Where h is the Planck's constant, which is 6.626 × 10 ^-34 joule‧s; c is the speed of light, which is 3 × 10 ⁸ m / s, and λ _{n is} substituted into the middle or average value of the wavelength range of each band.

When the light source to be tested is a sunlight light source and the analog light source is to be corrected, the following steps are performed: comparing the intensity difference between the light source to be measured and the solar spectrum in different wavelength bands, as in step S240, and determining whether the error exceeds one by one. The allowable range, if yes, is intensity corrected for the band of the solar simulated light source, as in step S245.

The present invention has the following advantages:

(1) The present invention provides a simple but effective method for estimating an approximate spectrum of a light source to be measured. The finer the wavelength of each band, the closer the approximate spectrum is to the actual spectrum. Of course, the premise is the reflectance of each band. And IQE must be obtained first. You can save a huge amount of money to buy a spectrometer.

(2) Spectral analysis of the light source to be measured at any predetermined time can avoid premature replacement (wasting money) or too late (the light source is aging, resulting in incorrect classification and being complained.)

(3) It is possible to further analyze whether the standard sheet has an offset problem.

Although the estimated photon flux for each band is an average, in the future, in the solar cell industry, manufacturers do not necessarily need to spend time and money, and then send the solar cells abroad for testing. Instead, directly in the instrument of the solar light source, a few solar cells can be used to detect whether the solar light source and the solar spectrum have too much error, resulting in a misjudgment of the efficiency of the solar cell.

The present invention has been described above by way of a preferred example, but it is not intended to limit the spirit of the invention and the inventive subject matter. Those who are familiar with the technology can easily understand and utilize other components or methods to produce the same effect. Modifications made without departing from the spirit and scope of the invention are intended to be included within the scope of the appended claims.

Figure 1 shows the solar spectrum and the solar spectrum; and

Figure 2 shows a flow chart of an embodiment of the invention.

10. . . Solar spectrum

11. . . Solar light analog light source spectrum

S200, S205, S210, S215, S220, S225, 230, 235, 240, 245, 250. . . Process steps of the embodiment of the present invention

S200, S205, S210, S215, S220, S225, 230, 235, 240, 245, 250. . . Process steps of the embodiment of the present invention

Claims (6)

A method for obtaining an approximate spectrum of a light source to be tested, comprising: dividing a wavelength range λ _a to λ _{b of} the approximate spectrum into n bands; providing the same number of solar cells N according to the number of divided bands, wherein each Each of the solar cells has an antireflection film layer or an internal quantum efficiency of different thicknesses; respectively, the internal quantum efficiencies of the solar cells at each wavelength band are respectively measured; and the average reflectance of the solar cells at each band is respectively measured Illuminating the solar cells with the light source to be measured to measure the output current, wherein the light intensity of the light source to be tested is at a predetermined value; respectively, the average photon flux of the solar cells at the bands is listed, The relationship between the average reflectance (1-reflectance) at these bands, the internal quantum efficiency at these bands, and the output current. The equation is that the output current is proportional to the average photon flux at the bands. The sum of the average antireflection rate at these bands and the internal quantum efficiency at these bands, where the average photon flux at these bands is unknown The above relationship simultaneous equations and solving the plurality of unknowns; and according to the average photon flux in the wavelength band of these bands is plotted relative to the plurality of the light source approximately measured spectrum. The method of claim 1, wherein the predetermined light intensity is about one of 100 to 3000 W/m ² . The method of claim 1, wherein the light source to be tested is a solar light source, λ _a = 300 nm, λ _b = 1200 nm, the intensity of the simulated light source is 1000 W/m ² , and n is at least Greater than or equal to 6, the method further comprises: comparing the difference between the average light intensity of the simulated light source and a solar spectrum in different bands; determining whether the difference exceeds an error tolerance range, and if so, continuing the following steps; The intensity correction is performed for the wavelength band in which the solar light analog light source differs beyond the allowable range of the error. The method of claim 1, wherein the thickness distribution of the anti-reflection film layer of the solar cell is such that the average anti-reflectance minimum values of the solar cells fall at different positions of the bands. The method according to claim 1, wherein if the number of the solar cells is six, the thickness of the solar cell anti-reflection film layer is about 50 nm, 60 nm, 70 nm, 80 nm, 90 nm and 100 nm, respectively. The method of claim 1, wherein when the solar cell is selected, internal conversion efficiencies of the solar cells in the same band are different.